Introduction

Traditional herbal medicine practitioners have detailed the therapeutic usefulness of several indigenous plants for various ailments. Indigenous plants are still used as a primary health care system in different parts of the world, where local empirical knowledge about plant medicinal characteristics serves as the foundation for their usage as a home medicine and continues to bring novel treatments to humans. Advances in separation and characterization technology have offered practical tools to the active constituents of medicinal plants and specifically identified the biologically active compounds, which rendered the use of whole plants as a drug to treat particular diseases unacceptable. Metabolomics is the most recent and well-integrated specialty that contributes to this field. Metabolomics has rapidly progressed and significantly impacted both fundamental and applied sciences (Oliver et al. 1998).

The prevalence of atopic disorders (AD) such as asthma, allergic rhinitis, atopic dermatitis, and food allergy has steadily increased over the previous 10 years, with the highest incidence for asthma, followed by allergic rhinitis. Atopic dermatitis, and food allergy, respectively, affects about 15–20% of children and a population of about 2–10% of adults (Capozza et al. 2023). Impaired immune system function and persistent inflammation increase vulnerability to repeated respiratory infections. AD represents a health burden to patients due to the high treatment costs besides the inability to perform daily regular work (Allenova and Darlenski 2023). Until now, AD treatments target inflammation using local-acting corticosteroids and systemic immunosuppressive medications (Tham and Leung 2019).

Dexamethasone (DEX) is regarded as a potent corticosteroid widely used to treat inflammations caused by several diseases. DEX has proven its efficiency in managing postoperative inflammations, notably when other therapeutic agents have failed to provide treatment benefits. However, the use of DEX has many drawbacks, such as a short half-life that requires repetitive administration of the drug and multiple side effects with prolonged use like hypertension, hydro electrolytic disorders, hyperglycaemia, peptic ulcers, and glucosuria; this limits the use of dexamethasone in long-term treatment (Schimmer and Parker 1996).

As a potentially safer alternative to topical terpenes, tripenes and steroids from natural products (Mohammed 2023) such as Boswellia carterii i volatile and fixed oils can be used in cases of inflammation associated with allergy due to their anti-inflammatory effects (Borotová et al. 2023). Trees in the Boswellia genus are prized for their fragrant resin, which has several medicinal uses, most notably as anti-inflammatory drugs. Components of the resin called boswellic acids have showed promise in the management of inflammatory disorders, such as asthma (Yassin et al. 2013).

For a long time, the development of new systems has required sophisticated chemistry, which has mainly thwarted efforts to create effective targeted mechanisms for delivering drugs. The development of the Nanocomposite Spongey delivery system for drugs has shown to be a big step in the right direction. Nano sponges (NSs) are a novel method for medicine administration. They are nanoscale sponge-like structures with several chambers capable of holding drugs. NSs are colloid structures made of polymers that are highly cross-linked being capable of distributing payloads owing to its porous exterior surfaces. Lipophilic and hydrophilic pharmaceuticals can be held in these polymeric sponge-like structures, enhancing the aqueous solubility and bioavailability of poorly soluble medicines (Girigoswami and Girigoswami 2022).

Because of their distinctive three-dimensional network and functional groups, NSs based on cyclodextrin are currently widely employed in the pharmaceutical sector to interact with biological tissues and promote bio adhesion. The targeted location can be reached by these small sponges passing through the body; once there, they adhere to the surface and begin releasing drugs gradually and accurately. Since the drug may be released at the precise target site rather than dispersing throughout the body, it will be more effective for a given dosage. Another significant feature of these sponges is their aqueous solubility, which enables successful application of these systems for medications with low solubility (Utzeri et al. 2022).

This work aims to fabricate a locally acting nano-composite delivery system loaded with DEX or BC oil mixture. The new system can be used to alleviate signs and symptoms of allergic rhinitis that occur as a part of AD in an attempt to prevent progression to bronchial asthma. Nano-composite delivery systems can enhance the efficacy of loaded drugs, avoiding severe side effects accompanied by oral administration, such as hepatic first-pass metabolism, gastric irritation, and compliance problems, and providing better treatment convenience.

Materials and methods

Materials

Boswellia carterii resins collected from Khartoum; Sudan governorate, this collection complies with local and national guidelines as permission was obtained for collection of plant material. Dexamethasone Sodium Phosphate was a gift from AMRIYA Pharmaceutical Industry Company, Egypt. Hydroxyprobyl β-cyclodextrin (HPβ-CD) (KLEPTOSE HPB, MW 1380) was kindly provided by Roquette (France). Diphenyl carbonate (DPC) was purchased from Acros Organics (Belgium). Prednisolone was purchased from Sigma Chemical Co. (St Louis, MO, U.S.A.). Disodium hydrogen phosphate anhydrous and Potassium dihydrogen phosphate were purchased from El-Gomhouria Pharmaceutical Chemicals (Egypt). Cellulose membrane was purchased from Sigma-Aldrich, chemie Gmbh, Steinheim, Germany. All other chemicals and solvent are of chemical grade and used without further purification. ELISA Kits for determination of allergic and inflammatory markers: Intracellular adhesion molecule 1(ICAM-1), Leukotriene B4 (LTB4) and Interleukinβ 4 (ILβ4) levels in serum were purchased from Elabscience Inc (USA).

Animals

Male Wistar albino rats weighing 150–175 g were obtained from the National Research Centre’s animal house colony in Dokki, Giza, Egypt. The rats were housed in common metal cages and kept in an air-conditioned space with a temperature of 22 °C and a humidity of 55°F with unlimited access to water. The current study complies with regional and federal regulations because it was carried out in accordance with the guidance for the care and use of laboratory animals and was granted clearance by the National Research Centre ethics committee under certificate number 19/209. The Institutional Animal Ethical Committee (IAEC) and the National Regulations of Animal Welfare in Egypt were followed when conducting the experiments, and the results were reported in line with Animal Research: In-Vivo Experiment Reporting (ARRIVE).

Methods

Plant extraction, volatile, and fixed oils from BC gum resin

Fixed and volatile oils are extracted substances from resin. The present study was carried out on Boswellia carterii resins collected from Khartoum; Sudan governorate. It was identified by Dr. Gibali, M.A. Department of Taxonomy, and Faculty of Science Cairo University then the estimation of volatile and fixed oil content (Rhimi et al. 2022). (i) The volatile oil of 50 g dry resins sample was extracted by the water distillation method (4 h) in a Clevenger’s apparatus (Guenther 1952). The resulted volatile oil of each treatment was separately dehydrated with anhydrous sodium sulphate and kept in the deep freezer until GC/MS analysis (Hamed et al. 2019). Each sample was done in triplicate and the mean values of the oil content (%) were recorded as 5.2 ± 0.8 ml. (ii) 355 g of air-dried fine powder of (BC) fruits were extracted by petroleum ether 40–60 °C using Soxhlet apparatus till complete extraction given 152 g. The extract was evaporated by rotary evaporator at 40 °C till dry, and then the residue was kept in vacuum desiccators till constant weight and total lipid content was calculated to be 42.25% (Rhimi et al. 2022).

Separating and classifying saponifiable and non-saponifiable substances

Two ml fixed oil was saponified (KOH) and determined (Kinsella 1966). The amount of fatty acid methyl esters was measured using GC/MS in the Chromatography unit at Bani Suef University, and it was used to establish a profiling list of fatty acid methyl ester metabolites (Mohammed et al. 2016). By contrasting the respective retention durations of the separated compounds with those of readily available reference compounds injected under the same circumstances, it was possible to identify the methyl esters of fatty acids, sterols, and hydrocarbon compounds. The area of the observed peak region served as the basis for the quantitative determination of each chemical (Mohammed et al. 2021).

Chromatographic procedure

Gas chromatography–mass spectrometry analysis (GC–MS)

Analyses were conducted using the GC–MS (Agilent Apparatus) at the Central Laboratories Network, National Research Centre, Cairo, Egypt. The equipment includes a gas chromatograph (7890B) and mass spectrometer detector (5977A). The GC was outfitted with an HP-5MS column that measured 30 m and had an internal diameter and film thickness of 0.25 mm. He was used as the carrier gas, with data being collected at the following temperature programmed and flow rates of 1.2 ml/min at a split of 1:30: 45 °C for 4 min; 4 °C/min increase to 150 °C and hold for 8 min; 6 °C/min increase to 210 °C and hold for 1 h. At 280 °C and 220 °C, respectively, the injector and detector were maintained by employing a spectral range of m/z 50–900 and a solvent delay of 5 min, mass spectra were produced by electron ionization (EI) at a power of 70 eV. By contrasting the spectrum fragmentation pattern with those found in the Wiley and NIST Mass Spectral Library data, many constituents were identified (Mohammed et al. 2022a, b).

UPLC-HRMS (lipidomic technique) of oils BC resins

One ml of methanol was added to 100 ul of oil from dried B. carterii resins extracted with petroleum ether. The extract was filtered before being mixed with a Q-Exactive hybrid MS/MS quadrupole—Orbitrap mass spectrometer (Thermo, Bremen, Germany) in negative ion mode. For the chromatographic separation of this system, deionized water acidified with 0.1 percent formic acid (solvent A) and acetonitrile (solvent B) were utilized, together with the BEH shield C18 column (1502.1 mm, 1.7 m). The mobile phase flow was changed to the following gradient for the duration of 5 min: (0–14 min) from 5 B to 50% B, (14–20 min) to 98 percent B. The system was then returned to its default settings and given three minutes to re-adjust. The Q-Exactive MS was operated at the following settings: the HESI ion source voltage (− 3 kV or 3 kV). The flow rate of the gas (N2) is 48 l/min, while the flow rate of the auxiliary gas is 13 l/min. The temperature of the auxiliary gas heater is 380 °C, whereas the ion source capillary is 250 °C. The CID MS/MS investigations’ collision energy was 15 eV (Mohammed et al. 2021).

Data processing

To give a thorough fragmentation pattern with retention time and MSMS information, mass spectral fragmentations of 50 metabolites were carried out using ion mobility tandem mass spectrometry (MSMS). The petroleum ether extract oil fractions were packed in MS-DIAL 4.90 (http://prime.psc.riken.jp/), which exported a common output ‘Analysis Base File’ (ABF) format from raw MS data import. Through the use of (MSP) format libraries to filter noisy spectra using a traditional spectral similarity computation, this resulted in an improved standardized untargeted lipidomic. By comparing the fragmentation patterns and retention indices (RI) of the chosen probable metabolites with those found in the KNApSAcK, Metlin, Golm, MassBank, Fiehn Bin Base, LipidBlast, ReSpect, and RIKEN databases, the metabolites were found and identified (Ammar et al. 2021; Mohammed et al. 2022a, b).

Preparation of nano sponges

A modified version of the ultrasound-assisted synthesis approach was employed to create NSs. Distilled water combined a specified molar ratio of diphenyl carbonate (DPC), a cross-linker, and hydroxypropyl cyclodextrin (HPβ-CD), a polymer. The ratios employed were 1:1, 1:3, 1:4, and 1:6 (HPβ-CD: DPC) (Table 5). The mixture was sonicated at 90 °C (Trotta et al. 2008; Abou Taleb et al. 2019), then homogenized in a hot water bath for 7 min at 12,000 rpm. The liquid was poured into falcon tubes and centrifuged for 30 min at 6000 rpm. After centrifugation, the drug was added, and the mixture was shaken at 150 rpm for the remainder of the night. The solution was centrifuged for 30 min at room temperature after being sonicated at 90 °C in the following day. The mixture was put into a petri dish, and the volume was adjusted for freeze-drying. It was then kept at 25 °C until it was used again. (Ansari et al. 2011b; Selvamuthukumar et al. 2012). The resulting Nano sponges will be uniformly sized and spherical in shape.

Determination of loading efficiency of NSs

NSs containing a precisely weighed quantity (10 mg) of DEX salt were stirred continuously in a 100 ml buffer solution (pH 7.4) for 50 min. Samples were filtered using a 0.22 m membrane filter before being analyzed with an ultraviolet–visible (UV) spectrophotometer (Pharma spec 1700, Shimadzu, Japan) at the preset λmax, at 242 nm (Al-Owaidi et al. 2021) The following equation was used to calculate encapsulation efficiency for all ratios:

$${\text{EE}}\% \, = \,\left( {M_{act} /M_{the} } \right) \times 100$$

where Mact is the actual DEX content in the weighed quantity of Nano sponges, and Mthe is the theoretical DEX content in Nano sponges (Kılıçarslan and Baykara 2003; Ahmed et al. 2021).

Vesicle size, polydispersity index and zeta potential measurement

The prepared formulations’ vesicle size, polydispersity index, and Zeta Potential were measured by the Zeta-sizer (Malvern Zeta-sizer Nano ZS, Malvern Instruments, UK) using dynamic light scattering (DLS), a method based on laser diffraction, at room temperature. At a scattering angle of 90.0°, the intensity of the scattered light’s time-dependent correlation function was measured (Abou Taleb et al. 2022).

Optimization of the selected NSs formulation

Following the completion of the tests, as mentioned earlier, the best molar ratio between HPβ-CD and DPC was selected to be the optimized ratio to prepare DEX salt NSs with the optimum EE%, PS and ZP values (D4). The same molar ratio HPβ-CD: DPC (1:6), was used for the preparation of BC mixed oils (1:1) extract NSs (O1). The new oil formulation was prepared as the same method previously mentioned in “Preparation of Nano sponges” section.

Determination of EE%, PS, ZP and PDI of Oil Ns formulation

The EE% of the prepared oil formulation was measured at the predetermined λmax, at 233 nm as previously mentioned in “Determination of loading efficiency of NSs” section. The composition, encapsulation efficiency and physico-chemical properties of the optimized formulations are presented in Table 5.

Characterization of the optimized formulations

Surface morphology

Transmission electron microscopy (TEM)

Using TEM (JEOL Co., JEM-2100, Japan), the morphological properties of DEX and Oil NSs were investigated. A copper grid that had been coated with carbon was given one drop of the diluted sample, and the grid was allowed to dry for 15 min at room temperature before the samples were stained. The grid was coated with a tiny amount of phosphotungstic acid solution (1%w/v), let to stand for three minutes, and then put into the microscope, where samples were inspected for surface features and shape at various magnifications (Swaminathan et al. 2010).


Scanning electron microscopy (SEM)

SEM (Quanta FEG 250, ThermoFisher Scientific Co., Czech Republic) was used to examine the surfaces of the optimized formulations. Freeze-dried samples were double-sided taped on aluminum stubs before being sputter-coated a thin coating of gold. At a distance of 10 mm and an acceleration voltage of 20 kV, SEM was employed (Abou Taleb et al. 2022).

X-ray powder diffraction

To examine the impact of inclusion complex phenomena on the drug’s crystallinity, the XRD spectra of DEX and oil NSs, as well as individual components such HP-CD, DPC DEX salt, and oil extract, were taken using a high-power powder X-ray diffractometer (Seimens, Model D5000, German). Quartz was used as the calibration internal standard. Powdered samples were subjected to Ni-filtered (Cu-k) radiation given at a 45 kV voltage and 40 mA current. Between 4 and 50 degrees, samples were examined. The recording employed a 2 o/min scanning speed with a 0.02 o step size. Calculated was the crystallinity’s % (Shankar and Agrawal 2015).

Fourier transform infrared spectroscopy analysis

To find out if there were any possible drug interactions with the components of the selected NS formulations, Fourier transform infrared spectroscopy (FT-IR) analysis using the KBr pellet method and an FT-IR spectrophotometer (JASCO 6100, Tokyo, Japan) was utilized.

In-vitro release study

This study employed free DEX, oil solutions, and DEX and oil NSs formulations (D4 and O1). The dialysis bags (Dialysis tubing cellulose membrane, Sigma-Aldrich Co., St. Louis, USA; Molecular weight cut-off 12,000–14,000) were filled with amounts equal to 2 mg of the NSs formulations, DEX, and oil aqueous solutions, and the cut-off value for molecular weight was 12,000–14,000. Before being put into 100 ml screw-capped glass containers filled with 100 ml PBS pH 7.4 to preserve sink condition, the bags were sealed on both sides to prevent leaking. The experiment was conducted in a thermostatic shaking water bath (Memmert, SV 1422, Germany) at 37 ± 0.5 °C and 100 rpm. Regular sample replacement with a similar amount of replacement release medium was done to maintain the sink condition. The DEX and oil concentrations were determined by spectrophotometric analysis and compared to blanks that had undergone the same treatment. The cumulative release percentages were calculated by dividing the drug release by the medication’s initial concentration in the dialysis bag. Each measurement was carried out in triplicate, and three separate samples were used. Numerous mathematical models, including zero, first order, Higuchi’s square root of time model, and Krosmeyr Peppa’s kinetic models, were used in the kinetic analysis of drug release from NSs formulations (Basha et al. 2015).

Pharmacological study

Experimental design of the efficacy study

Male Wistar albino rats were used for the biological evaluation of the formulations’ efficacy. Forty-eight rats were divided into 6 groups at random (n = 8). Rats in group I acted as the negative control group and received oral saline solution 0.9%. For the duration of 120 days, Group II was given acetaminophen suspended in yoghurt via oral gavage in order to induce allergic rhinitis (Mohammed et al. 2022a, b) and served as a positive control group. Groups III, IV, V and VI received acetaminophen as group II, then they were treated with a dose of 10 µl equivalent to 20 µg of Free BO extract, Free DEX, DEX NSs and BO NSs, respectively instilled in each rat’s nostril (IN) for 28 days.

Preparation of blood samples and biochemical analysis of anti-inflammatory and anti-allergic markers

At 24 h following the final therapy dosage, blood samples were taken from all rats’ retro-orbital plexus veins. Samples were centrifuged at room temperature for 10 min at 1500 rpm to separate the serum after clotting (Sorg and Buckner 1964). Serum samples were stored at − 20 °C for analysis of intercellular adhesion molecule-1 (ICAM-1), interleukin β 4 (ILβ 4) and Leukotriene B4 (LTB4) and levels in serum by using ELISA kits.

Preparation of tissues for Histopathologic examination

All groups were sacrificed. Each animal’s nose, trachea, and lungs were removed, fixed in 10% neutral formalin solution for 24 h, and then embedded in paraffin. After being rinsed in tap water for 30 min, all specimens were dehydrated in varying amounts of alcohol, cleaned in xylene, and embedded in paraffin. Hematoxylin and eosin were used to stain serial slices each three millimeters thick (Drury and Wallington 1980) to be examined histopathologically. Images were taken at the National Research Centre’s pathology lab utilizing an image analysis system with an Olympus CX41 light microscope and an SC100 video camera connected to a computer system. Numerous photomicrographs were captured at various magnifications.

Statistical analysis

Values were given as means ± standard error. One-way analysis of variance (ANOVA) was used to compare means, followed by the Tukey–Kramer multiple comparisons test. In all varieties of statistical tests, p ≤ 0.001 was considered as being significant. All statistical analyses were performed using GraphPad Prism software, version 8.

Results and discussion

Volatile oil extraction and chromatography of B. carterii resins by GC/MS

Trees in the genus Boswellia provide the resin used to make essential oils (family Burseraceae). To develop exuded gum, which looks like a milk-like resin, cuts are made in the tree trunks. The resin becomes frankincense, an orange-brown gum resin that has dried. B. carterii grows in Sudan, and China, and B. sacra grows in Arabia. It has been used by ancient Egyptians, and the aroma of these resins has been esteemed for its putative therapeutic effects and excellent qualities for religious ceremonies (DeCarlo et al. 2020). Numerous health-promoting qualities of frankincense resin have been thought to exist throughout history. Rheumatoid arthritis and other inflammatory disorders have been treated with the resins of the Boswellia serrata in many different cultures (Lindler et al. 2020).

In the First way of extraction; Volatile oils extracted from BC resin by steam hydro distillation are given yield 10.4%. According to GC/MS analysis, the recognized constituents of the essential oil are presented in (Table 1 and Fig. 1a). The resins of BC essential oil composed of forty-seven compounds representative of 94.4% of the total oil constituents. The main ingredients of the essential oil identified with GC/MS are Octyl acetate (46.46%, peak no. 18) and 3-Carene (6.37% peak no. 12), and D-Limonene (5.25% peak no. 14) and Farnesyl acetate (5.05 peak no. 31). The total amounts of the four major compounds in the volatile oils were 63.13 from 94.04% showed in (Table 1 and Fig. 1a). The oxygenated compounds were 66.61% more than non-oxygenated compounds 27.79%. When comparing the yield% with the other different studies that reported that frankincense resin contains 5–11% of essential oil, it was found that there is a similar correlation with the amount extracted by steam distillation (Al Amri et al. 2019; Ayub et al. 2022). We found that the main constituent of volatile oils resins is Octyl acetate (46.46%, peak no. 18), which was different from previous study performed by Ni et al., who uncovered that alpha-pinene 78.45% is the main constituent in B. sacra, which may be due to study of different species (Ni et al. 2012). In this respect, the results is nearly similar to that obtained by Hussain et al. (2013) and Mikhaeil et al. (2003), who mentioned that the major compounds in B. carterii was octyl acetate (13.4–40%) then Limonene, α-pinene, and octanol.

Table 1 The main chemical constituents of volatile oil Boswellia Carterri
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Fig. 1
figure 1

a TIC chromatogram of the volatile oil BC resins, b TIC chromatogram of the saponification fixed oil BC resins, c TIC chromatogram of the Unsaponification fixed oil of Boswellia Carterri fruits

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Lipid profiles of B. carterii resins by GC/MS chromatography

In the second extraction procedure, the Soxhlet apparatus extracted 355 g of resin fruit with petroleum ether (40–60 °C) as a total lipid extract. Using a rotating evaporator and lowered pressure at 35 °C, the mixed extracts were concentrated (Ayub et al. 2023) and filtered using Whatman No. 54.

Saponification of the fixed oil of BC-resins

The results in Table 2 and TIC in Fig. 1b represented the forty-four fatty acid methyl esters of different BC resins under investigation. MS was used in this investigation for the qualitative and quantitative determination of individual fatty acids. The major five fatty acids were estimated 46.44% from total lipids as follow: β-Boswellic acid (10.21%), Oleic acid (10.05%), 3-O-acetyl-β-boswellic acid (8.98%), Myristic acid (8.89%), and 11-Keto-beta-boswellic acid (8.31%).

Table 2 The main constituents of saponification fixed oil BC resin
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Unsaponification of the fixed oil of BC-resins

The unsaponifiable lipid fraction is a potential source of bioactive components such as, acetophenones, triterpenoids, and various hydrocarbons compounds. GC–MS analyses of the unsaponifiable matter of the BC resins are presented in (Table 3 and Fig. 1c). The highest four compounds are recorded as 4′-Methylacetophenone (47.11%), Squalene (20%), Campesterol (10.15%) and d-Limonene (6.41%). The results revealed the presence of various hydrocarbons ranging from C9 to C31, of which Hydrocarbon Resin C9, dodecane C12, Octacosane C28, and Hentriaconta C31 are the most predominant components. Dealing with percentage the unsaponifiable matter represented the percentage of 83.68% for four compounds from the total thirty-three compounds from the unsaponifiable lipid.

Table 3 The unsaponification fixed oil of Boswellia Carterri fruits
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Lipidomic profiles of the fixed oil of BC- resins by LC-MSMS

The lipidomic profiles of the 50 substances examined by LC-MSMS of BC were documented in Table 4 and graphically displayed in Fig. 2 (Mohammed et al. 2021).

Table 4 Lipidomic profiles of listed compounds by LC-MSMS
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Fig. 2
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Methods for the generation of molecular networks from lipidomic mass spectrometry using MS-DIAL (4.90) via data visualization then molecular spectrum networking data with the GNPS web platform for all signals compounds (15,19, 24 and 20) showed Norethisterone acetate compound

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Molecular network

When molecules are ionized using lipidomics mass spectrometry, they frequently form multiple ion species with distinct fragmentation behavior. MS-DIAL (4.90) is a method for creating molecular networks from these data. Next, molecular spectrum networking data is created using the GNPS web platform for all signals, and Fig. 2 displays a list of compounds (Mohammed et al. 2021).

Preparation of DEX NSs

In the present study, NSs were prepared by ultrasound assisted technique. This method produces NSs with spherical shape and uniform in size (Trotta et al. 2008). Table 5 lists the components of the four formulations as well as the conclusions drawn from the evaluation of the responses. The formation and functionality of NSs are influenced by the kind of polymer used in their manufacture. Similar to the combination formed between the polymer and the crosslinker, the cavity size should be enough for conveying a drug molecule of a particular size (Selvamuthukumar et al. 2012).

Table 5 Composition, entrapment efficiency and physico-chemical properties of DEX salt and oil extract NSs
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Cyclodextrin-based Nano sponges have gained popularity recently due to their unique properties. By forming inclusion complexes through the inner nanocavities of cyclodextrins and non-inclusion complexes through the gaps in the sponges’ cross-linked polymeric network, these sponges specifically increase the stability and apparent solubility of medicines. NSs made with cyclodextrins (like HPβ-CD) can offer a promising class of cross-linked polymers with a remarkable three-dimensional architecture made of both hydrophilic and hydrophobic nanosized pores that can successfully encapsulate a variety of drugs and increase the solubility of drugs that aren’t very soluble (Swaminathan et al. 2009). Additionally, they have been shown to be secure for use with various administration methods, making them a viable drug delivery strategy (Vyas et al. 2008a, b). To increase the effectiveness of the drug loading and solubilization, the ratio of cyclodextrin to cross-linker can be adjusted during the manufacture of NSs. In the current investigation, DEX NSs was made using HPβ-CD as the polymer and DPC as the crosslinker in various ratios (1:1, 1:3, 1:4, and 1:6). In all the formulations that were looked into, NSs were prepared effectively.

Encapsulation efficiency

Table 5 shows the EE% values for all DEX NSs formulations. The EE% values for all formulations ranged from 99.15 ± 3.50 to 100% ± 4.76%. It was clear that all prepared NSs had high encapsulation efficiency (EE%), confirming the success of DEX NS preparation. The high EE% of the produced NSs could be attributed to optimal cross-linking between HPβ-CD and DPC, allowing for high inclusion of DEX salt in the NSs matrix and cyclodextrin cavity (Olteanu et al. 2014; Kumar et al. 2018). Along with the inclusion of DEX salt in the porous matrix of the Nano sponge, Additionally, it is responsible for completely trapping the drug molecules as an inclusion complex inside the hydrophobic host cyclodextrins’ cavities, which are encircled by hydrophilic nanochannels (Trotta et al. 2012; Kumar et al. 2021).

Vesicle size, polydispersity index and zeta potential

The analysis of DEX NSs revealed that all produced NSs were in the nanosized range, with formulation sizes ranging from 59.9 ± 26.3 to 159.2 ± 20.2 nm (Table 5). Since the increase in cross linking agent molar ratio resulted in greater PS, it was discovered that formulations with a higher molar ratio of cross-linker had larger Vesicle diameters than those with a lower molar ratio of cross-linker (Yaşayan et al. 2020). Additionally, the data supported low polydispersity index (PDI) values of 0.265 to 0.675, indicating a uniform and constrained vesicle size distribution.

Table 5 further demonstrates that all of the formulations under investigation displayed a negatively charged zeta potential, which may have been caused by the free hydroxyl groups in HP β-CD and the carbonyl groups in DPC (Zidan et al. 2018; Omar et al. 2020). Absolute ZP values of greater than 20 were found for all formulations under consideration, and these values are more than sufficient to keep the individual particles apart from one another due to electrostatic repulsion. In contrast it keeps the stability of the prepared formulations (Abou Taleb et al. 2022).

Selection of the optimized DEX salt and oil NSs formulations

According to EE%, PS, PDI and ZP results, the best molar ratio between HPβ-CD and DPC was selected as the optimized ratio to prepare DEX salt NSs (1:6) (D4). The same molar ratio HPβ-CD: DPC (1:6), was used to prepare mixed oil extract NSs (O1). The λmax of the oil extract was found to be at 233 nm. The EE%, PS, PDI and ZP of the new oil formulation were estimated and demonstrated in Table 5. It was found that the new oil Ns formulation exhibited high EE%, with particle size in the nano range, low PDI and suitable ZP value.

Characterization of the optimized formulations

Surface morphology

Transmission electron microscopy (TEM)

Figure 3a depicts the morphology of DEX and Oil NSs. The NSs are round and uniform, with no drug crystals on the surface. According to the figures, the NSs created using the ultrasonic- assisted processes have a uniform size distribution, crystallinity, and a porous character (Mahalingam et al. 2017).

Fig. 3
figure 3

a TEM micrographs of Nano sponges optimized formulations (D4 and O1), b SEM micrographs of Nano sponges optimized formulations (D4 and O1)

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Scanning electron microscopy (SEM)

The SEM images of DEX and Oil NSs are illustrated in Fig. 3b. SEM analysis of the prepared NSs revealed nano-sized spherical particles having multiple pores on their surface (Muqtader et al. 2021). There were no residual crystals from the drugs indicating the complete encapsulation of drugs in the polymer (Sharma et al. 2011).

X-ray diffraction

The crystallinity of the Nano sponge formulations was determined using powder XRD. A diffractogram’s peak position (angle of diffraction) is used to determine a crystal structure, and the number of peaks is used to assess sample crystallinity. The creation of an amorphous state indicates that the medication was diffused molecularly with CD (Patel and Rajput 2009). X-ray diffractometer plots of HPβ-CD, DPC, DEX Salt, Oil Extract and optimized NSs formulations (D4 and O1) are existing in Fig. 4a. The HPβ-CD diffractogram reveals the presence of two big diffraction peaks at 10.5° and 19.5° (Han et al. 2020), they lack structure but disclose the presence of a distant disorganized crystal structure and its amorphous nature (Nikolić et al. 2013; Paczkowska-Walendowska et al. 2020). DPC diffractometer showed sharp peaks as an indication on its crystallinity nature. DEX Salt and BO extract diffractometers showed that the drugs are crystalline, and have a polymorphic form with distinct sharp peaks (Qnouch et al. 2021).

Fig. 4
figure 4

a X-Ray diffractometer of different Nano sponges components and optimized formulations, b IR spectrum of different Nano sponges components and optimized formulations

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Compared to the pure pharmaceuticals, the drug-loaded Nano sponges (D4 and O1) diffractometers demonstrated a weakening or elimination of powerful peaks when diffractograms of individual components and NSs formulations were examined. This reveals unequivocally how drug dispersion in NS polymer causes crystals to change into amorphous form. The polymeric enclosing layers constrain the drug film, which prevents crystallization at the air–solid junction. As a result, the coating layer includes an additional solid–solid barrier. This is known as an amorphous solid dispersion, and it is almost probably the result of drug-polymer interactions developing as a result of the drug’s crystal lattice’s intermolecular connections being broken down (Almutairy et al. 2021). This confirmed that medicines were entirely incorporated into the cavity of 2HPβ-CD, and the success of Nano sponge fabrication (Ansari et al. 2011a; Nikolić et al. 2013; Mahalingam et al. 2017).

Fourier transform infrared spectroscopy analysis

The interactions between pharmaceuticals and excipients were investigated by comparing the FTIR spectra of pure drugs with drug-loaded Nano sponges (D4 and O1) (Fig. 4b). The FTIR spectra of HP-β-CD showed prominent absorption bands at 3415 cm−1 (O–H stretching), 2929 cm−1 (C–H stretching), 1645 cm−1 (H–O–H bending), 1157 cm−1 (C–O stretching), and 1031 cm−1 (C–O–C stretching) (Gidwani and Vyas 2015; Han et al. 2020). FTIR spectrum bands for DPC revealed distinctive absorbance band at 1753 cm−1 for carbonate bond (Dubey et al. 2017). DEX exhibited distinct absorbance bands at 1706, 1660, and 1616 cm−1, which were attributed to –C=O stretching vibrations connected to C3-cyclic and C20 carbonyl groups, as well as double bond context coupled to –C=O bonds. Furthermore, two more different absorption bands of 3468 cm−1 and 1270 cm−1 were realized due to the stretching ambiences of the O–H and C–F bonds, respectively (Rodrigues et al. 2009; Long et al. 2019).

The IR spectrum of BO extract is comparative to Boswellia acids and it displayed characteristic peaks at 3437 cm−1 (OH stretching), 2932 cm−1 (C-H stretching), 1697 cm−1 (C=O stretching of aryl acid), 1453 cm−1 (C–H bend), 1375 cm−1 (COO symmetric stretching of carboxylates), 1240 cm−1 (C–CO–C stretching of aryl ketone), 1025 cm−1 and 988 cm−1 (ring structures of cyclohexane) (Mehta et al. 2016).

In the distinctive peaks of DEX or Oil extract, the IR spectrum of the optimized Nano sponge formulations (D4 and O1) revealed a shifting and diminished intensity. This shift in the characteristic peaks may be explained by the presence of physical interactions between drugs and various NS elements, such as Van der Wall bonds, hydrogen bonds, or dipole interactions, without any chemical changes to the drugs’ structure after encapsulation, which can result in the best possible entrapment of DEX or Oil in Nano sponges (Mazyed and Zakaria 2019; Omar et al. 2020; Younis et al. 2023).

In-vitro release study

CD-based NSs can be a valuable technique for delivering medications in a sustained manner. Drug encapsulation in a cross-linked NSs structure allows for prolonged drug administration, lower doses, fewer side effects, and changed pharmacokinetics. These characteristics can be used to improve medicine distribution (Osmani et al. 2018).

The produced NSs formulations and the free drug solutions’ DEX salt and Oil extract release profiles were shown in Fig. 5. The release profiles of the tested formulations displayed a biphasic behavior, with an initial quick-release lasting for the first six hours. This first rapid release may have been caused by the drug’s adsorption on the NSs’ surface vesicles, which led to a fast release from NSs (Sunil et al. 2019). Followed by a delayed, slow release for 24 h. On the other hand, about 100% of DEX salt and oil extract were liberated from the free drug solution after 6 h (Fig. 6).

Fig. 5
figure 5

In-vitro release profiles of drugs from Nano sponges optimized formulations (D4 and O1)) and free drugs at PBS 7.4

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Fig. 6
figure 6

Photomicrographs of lung, tracheal and nasal tissues of a Negative control, b Positive control, c Boswellia Oil, d DEX salt, e DEX salt Nano sponges (D4) and f Oil extract Nano sponges (O1). Black arrows; alveoli with average thickness wall, Dashed red arrows; congested blood vessels, A; Alveoli, B; bronchioles, B*; bronchioles filled with mucus, INF; inflammatory cells infiltrates, Black stars; ciliated pseudostratified columnar epithelium, Yellow stars; hyperplastic columnar epithelium, TC; tracheal cartilage, PSE; pseudostratified epithelium. All photomicrographs were taken at two magnification powers (× 200 and × 400)

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Frequent administration is the main disadvantage of the majority of the traditional, commercially available drug delivery devices. The medication, however, is kept and released gradually over time after being loaded into the Nano sponge. It has been previously reported that hydrophilic cyclodextrin Nano sponges are used to adjust the drug release rate, as it facilitates medication absorption over biological barriers and it may help to protect the medication throughout its passage through the stomach (2008a, b; Abou Taleb et al. 2019).

NSs formulations’ correlation coefficient (R2) values showed better fitting to Higuchi’s model than zero order and first order kinetic models, according to a linear regression analysis of the mathematical models used for release information gathered from NSs formulations (R2 ranged from 0.8634 to 0.9865). The Peppas equation was used for further examination of the DEX and oil release process (Peppas and Sahlin 1989; Lokhande et al. 2013) when high linearity was observed. According to Peppas theory, if n = 0.43, drug release follows the Fickian diffusion process, 0.43 < n < 0.85 follows anomalous (non-Fickian) diffusion, n = 0.85 follows case II transport, and n > 0.85 follows super-case II transport (Peppas and Sahlin 1989). Values of the release exponent “n” for NSs formulations ranged from 0.117 to 0.3568, respectively, indicating a Fickian diffusion-controlled release mechanism.

In-vivo pharmacological study

Effect of different formulations on inflammatory and allergic mediators of respiratory tract

Results in Table 6 revealed the biochemical analysis of the intercellular adhesion molecule-1 (ICAM-1), inflammatory marker Ilβ4, and the chemokine Leukotriene LTB4. All indicators considerably increased in the positive control group compared to the negative control group. Intranasal instillation of different medications for treating allergic rhinitis in rats showed different effects on the levels of biological markers.

Table 6 Effects of treatment with Boswellia carterii volatile oil, Dexa salt and their Nano Sponge formulations on inflammatory and allergic mediators of respiratory tract
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The function of ICAM-1, is crucial in the disease progression of the inflammatory allergic rhinitis. Its expression in epithelial cells of the nasal cavity during allergic rhinitis is considered the main feature of allergic reaction. It is used for the prognosis of the disease and evaluation of its severity (Bianco et al. 2000). In the case of ICAM-1, results showed that the effect of treatment on inhibition of its level were in the order of BO > D4 > O1, while treatment with free DEX elevated the levels of ICAM-1. The potent chemokine Leukotriene Ilβ4 is an allergic inflammatory marker that is a metabolite of arachidonic acid. It acts by enhancing the aggregation of neutrophils. When it is activated, it causes accumulation of inflammatory and immune effector cells in addition to its action on T cells in the immune response, leading to potentiation of the release of cytokines (Bocsan et al. 2021). Results showed that the effect of treatment on inhibition of the Ilβ4 level were in the order of O1 > BO > D4. Treatment with free DEX not enough of an appeal to make a difference on Ilβ4 levels. Leukotriene B4 (LTB4) is an important component of tissue injury and inflammation and a potent lipid mediator that is essential for the proliferation and recruiting of neutrophils (Asahara et al. 2022). Results showed that both BO and BO in Nano sponge have a significant effect on the inhibition of LTB4 levels, while treatment with free DEX and DEX Nano sponge didn’t appeal to have a significant effect on LTB4 levels. In the present work, the best effects as a whole were those of B. carterii mixed oil, B. carterii mixed oil in Nano sponge (O1) and Dexa salt in Nano sponge (D4) as they reduced ICAM-1 and Ilβ4 levels significantly.

Different symptoms of inflammation include redness, heat, pain, swelling, and a reduction in function. Numerous inflammatory mediators like ICAM-1, Ilβ4 and LTB4 are produced, which causes these symptoms to appear. It has been previously reported that, numerous medicinal plants such as Boswellia species have anti-inflammatory activity as Boswellic acids derived from them works on inhibiting the synthesis of prostaglandins by interfering with the cyclooxygenase system and the arachidonic acid cascade, which subsequently can inhibit the production of leukotrienes and thus can control the progress of inflammatory diseases like chronic asthma bronchitis and rhinitis (Ammon et al. 1993).

Results obtained on treatment with DEX salt can be explained in light of the study of Bocsan et al., who revealed that ICAM-1 levels were greater in patients sensitized with pollen grains and suffering allergic rhinitis, than non- sensitized individuals during pollen exposure. On the other hand, treatment with antihistaminic therapy didn’t lower their levels in sera during pollen season (Bocsan et al. 2021). In a related investigation, Vestbo and associates prospectively tracked 290 individuals with mild to moderate chronic obstructive pulmonary disease (COPD) and discovered no variation in the pace of inflammatory mediator decrease. In this patient cohort, the rate of exacerbation did not reduce with the use of inhaled corticosteroids (ICS) (Vestbo et al. 1999). The results of the Lung Health Study in many aspects confirmed those previously reported on the lack of impact of ICS on lung function loss; nevertheless, there were beneficial side effects, such as reduced symptoms, fewer doctor visits, and less airway hyperreactivity (Wise et al. 2000). Loading of Dex in Nano sponges enhanced its therapeutic activity when compared to free drug, which may be rationalized by the sustained release of drug from Nano sponges that lead to prolonged activity and reduction of adverse effects (Shrestha and Bhattacharya 2020).

Histopathological examination

The Histopathological examinations of the lung, trachea and nose from different groups are illustrated in Fig. 6. The figures revealed that the lungs of negative control rats (Fig. 6a) are more like a well-organized sponge consisting of functional respiratory units alveoli. Each alveolus shares its wall (interalveolar septum) with adjacent alveoli they are average in thickness, bronchioles lined by columnar epithelium supported by smooth muscle layer have normal appearance, bronchial vessels have normal looking and average thickness, examination of tracheal tissue revealed that it is lined by ciliated, pseudostratified columnar epithelium, rests upon ordinary connective tissue, Incomplete rings of hyaline cartilage encircle the trachea and photomicrographs of nasal tissue revealed that the nasal cavity lined by pseudostratified epithelium (PSE) mucosa and submucosa region filled of blood vessels, mucin and serous secreting gland.

On the other hand the positive group tissue examinations (Fig. 6b), exhibited disturbed lung architecture and severe infiltration of lung tissue with inflammatory cells some with focal formation, indentation of bronchial lining with evidence of intrabronchial mucus presence, bronchial vessels are congested with increased thickness, the trachea is lined minimally destructed pseudostratified columnar epithelium infiltrated by inflammatory cells, nasal tissues showed disturbed mucosal region by edema and inflammatory cell infiltrate.

Histopathological examinations of tissues from the B. carterii mixed oil group (Fig. 6c) showed that the lung tissues are infiltrated with inflammatory cell infiltrates, especially around the bronchioles, which are filled with mucus and have indented walls. Histopathological examination of tracheal tissues revealed that the trachea is lined by ciliated, pseudostratified columnar epithelium with severe inflammatory cells infiltrated.

Also, histopathological examination of the lung tissue DEX group (Fig. 6d) showed that the lung tissues were destroyed mainly by severe infiltration of inflammatory cells with focal areas of mucin formation. Histopathological examination of tracheal tissue revealed that the tracheal lining is destructed and rests upon connective tissue infiltrated by inflammatory cells and the focal regions of mucin. Also, histopathological examination of nasal tissue showed destruction of nasal tissue by inflammatory cells infiltrating and focal areas of mucin.

Histopathological examination of tissues treated with DEX salt in Nano sponges D4 (Fig. 6e) revealed that the tissues retained the normal appearance of lung architecture, with only the bronchial vessels congested with increased thickness. On the other hand, the lungs treated with B. carterii mixed oil in Nano sponge group O1 (Fig. 6f) are more like a well-organized sponge consisting of functional respiratory units alveoli; each alveolus shares its wall (interalveolar septum) with minimal inflammatory cells infiltrate, bronchioles lined by columnar epithelium supported by smooth muscle layer has normal appearance, bronchial vessels have normal looking and average thickness. Histopathological examination of nasal tissues treated with D4 and O1 revealed that the nasal cavity is lined by pseudostratified epithelium (PSE), mucosa, and submucosa region filled with blood vessels, mucin, and serous secreting gland, with improvement in the thickening of nasal cavity lining.

Results obtained with histopathological examinations were in accordance with that observed with inflammatory markers measurements. Since the antiallergic anti-inflammatory mechanism of action of conventional Boswellia oil and its Nano sponge formulation is the same as that adopted by non-steroidal anti-inflammatory drug Dexa salt, which acts by suppressing inflammation, via inhibiting eicosanoid synthesis (Koeberle et al. 2018), therefore it is suggested that the tested natural products in our study are potent anti-inflammatory and anti-allergic agents and can be promising for alleviating signs and symptoms of allergic rhinitis as they significantly lowered the inflammatory biomarkers ICAM-1, Ilβ4 and LTB4 levels in comparison to free Dexa salt which can be attributed to sesquiterpenoids, diterpenes, and triterpenes present in Boswellia, particularly boswellic acids and other tirucallic acids. Moreover, Boswellic acids are pentacyclic triterpene acids that may be able to treat chronic conditions with an inflammatory component because they target cathepsin G and 5-lipoxygenase (5-LO) in neutrophils (Rainsford 2007; Siemoneit et al. 2009; Huang et al. 2022).

Conclusion

The successful extraction and characterization of volatile oil from B. carterii have been accomplished, and Nano sponges loaded with either B. carterii oil or Dex salt exhibits the most desirable characteristics essential for an effective dosage form. These Nano sponges, characterized by a small particle size, demonstrate continuous release profiles lasting up to 24 h. Moreover, they display a remarkable capacity to extend drug release duration, potentially leading to a reduction in drug administration frequency, lower medication dosages, and the avoidance of systemic adverse effects. Both B. carterii volatile oil, Dexa salt, and their nanoformulations (D4 and O1) were examined to evaluate the anti-inflammatory activity for treating respiratory allergies. Histopathologic examinations, along with measurements of Intracellular adhesion molecule-1 (ICAM-1), Leukotriene B4 (LTB4), and Interleukin β4 (ILβ4) levels, indicated a significant reduction in inflammatory biomarkers in treated rats.

Additionally, these treatments exhibited improved histopathologic profiles compared to the positive control group. Boswellia oil and its Nano sponge formulation O1 and Dexa salt Nano sponge formulation D4 demonstrated promising therapeutic effects in managing both upper and lower respiratory allergic conditions. These findings suggest the potential clinical benefits of utilizing these formulations for treating respiratory allergies.