1 Introduction

Food and nutrition researchers are looking for novel food items with positive impacts on health that may be created to increase longevity; the dry and semi-arid regions worldwide are home to various crops called Opuntia spp. The promising plants are known as Opuntia spp. Sometimes called cactus pear or prickly pear, many Opuntia species (family Cactaceae) produce higher water usage efficiency than C3 or C4 plants due to the crassulacean acid metabolism (CAM) that takes place in those plants [1,2,3,4,5,6,7,8,9]. As a result, FAO recommended Opuntia spp. as a strategic and unique plant worldwide, particularly for those that experience a shortage of water, to combat global climate change [www.fao.org/publications/card/en/c/cefa9d40-eb22-5ce8-a4fb-ade184d0b4ac]. The advantages of Opuntia spp. ecological allows CO2 absorption at night, which minimizes water loss during the photosynthesis. Numerous colors of Opuntia spp., including red, violet, green, and yellow, result from genetic variation [10, 11].

Several Opuntia spp. are known to be renowned weeds in various regions worldwide, while some species, like Opuntia ficus-indica, are professionally farmed for edible and feed uses [7, 8, 10,11,12]. Although Opuntia spp. originated in Mexico and is still widely grown there; it is also grown in other nations, including the Mediterranean region, the United States, India, and South Africa.

Opuntia ficus-indica, often called cactus or the prickly pear fruit, is a member of the Cactaceae family. It has a thick pericarp with numerous clefts filled with tiny prickles that are yellow, reddish purple, or white and a delectable, sweet pulp mixed in with several very little seeds. The average weight of an Opuntia ficus-indica fruit ranges from 45 to 250 g [13].

The Opuntia fruit is made up of a thick skin (40–60% of the fruit weight) that surrounds a pulp (30–60% of the fruit weight) that contains smaller seeds (2–10% of the fruit weight). Opuntia fruit pulp is the starting point for many manufactured food items like juices and jams [10, 11]. Opuntia ficus-indica seed oil is usually utilized in various meals, cosmetics, and pharmaceuticals, but fruit seeds contain significant lipid content. Some Opuntia spp. fruits include large concentrations of natural pigments that can be used for food coloring, such as yellow to orange betaxanthins and red to violet betacyanins. Additionally, Opuntia fruits have a significant quantity of distinctive plant mucilage, which acts as a thickener agent [1,2,3,4,5,6,7,8,9,10].

Fruit is highly flavourful and has strong nutritional characteristics. Fruits make edible items, including juices, jams, and natural liquid sweeteners. It has long been used to treat various health problems in addition to being taken as food or beverage. It has also recently been commercially manufactured as capsules, liquids, tablets, or powders. Opuntia ficus-indica is grown and cultivated in the Taif region, Kingdom of Saudi Arabia [14].

Opuntia ficus-indica fruits are a unique source of essential nutrients for animal and human nutrition and have several bioactive components, including fibers, vitamins C and E, several types of minerals, fatty acids, amino acids, and natural colors like betalain compounds [1,2,3,4,5,6]. Consuming fresh and/or processed Opuntia spp. fruits provide various health benefits. Opuntia spp. phytochemicals exhibited hepato-protective, antioxidant, anti-cancer, and anti-atherosclerotic traits. On the other hand, the peel, pulp, and seeds obtained during preparing Opuntia fruits contain many bioactive components. Meanwhile, because of genetic variation and several environmental factors, the levels of Opuntia ficus-indica active components vary [15].

This work aimed to review and highlight the information about the different compounds in the Opuntia plant cultivated worldwide, especially in Saudi Arabia, as well as their health effects.

2 Economic importance of Opuntia plants

Plant-based medications are extensively utilized for their efficacy, few side effects, and low environmental cost [11, 16]. The Kingdom of Saudi Arabia is abundant in flora, similar to Opuntia spp. Some of them have edible fruits with rich-colored pericarps and tasty flesh containing small seeds. While originally from Mexico, Opuntia ficus-indica is grown all over the world. In Saudi Arabia, the plant is grown in some sites for its edible prickly pear fruit, which locals consume.

What distinguishes Opuntia ficus-indica is that it thrives in badly deteriorated soils that are unsuitable for other plants and are perfect for adapting to environmental changes on a global scale [11, 16]. Thus, during the dry season, approximately all animals and livestock depend on consuming Opuntia planting. Moreover, because the Opuntia ficus-indica is common and extensive, the FAO organization start Cactus Fruit Development Project to enhance the process of cultivation, marketing and distribution; one of the strategies of the program is to identify and control some diseases by using Opuntia ficus-indica [17].

Opuntia plants are an important part of the agricultural systems and the global economy, considering their ripening and growing in harsh conditions [11, 16]. For example, Opuntia ficus-indica red and yellow cultivars are grown in Taif governorate, Saudi Arabia, known as "parchomy". According to the Ministry of Environment, Water and Agriculture in Taif, the production of Opuntia ficus-indica is estimated at about 1200 tons, starting in July of each year. In Saudi Arabia, efforts should be directed to increase production and introduce Opuntia to several food products. This stimulated increased studies to investigate the nutritional values of the pulp, peel, and seed [11, 16].

3 Opuntia ficus-indica nutritional composition

Minerals, pigments, fiber, sugar, amino acids, vitamins, and antioxidants are abundant in O. ficus-indica. The fruit biowastes or pomace (seeds and skin) are also a great source of nutraceuticals and functional food [1, 2, 11, 16]. Fruits from various species do not seem to have very distinct nutritional profiles. Most variations in prickly pear fruits result from human selections for greater size, longer shelf life, and better flavor.

Opuntia composition (Fig. 1) of different parts relies on some factors, including cultivar, species, weather, fertilization, soil, maturity, and postharvest handling and storage [1, 2, 7, 8, 11, 16, 18,19,20,21].

Fig. 1
figure 1

Nutritional composition (g/100g FW) of Opuntia ficus-indica (adapted from Silva et al. [21])

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Opuntia ficus-indica pulp contains high levels of moisture and sugar. Furthermore, compared to the seed and peel, fruit pulp of O. ficus-indica has less protein and fiber. The highest protein, lipids, and dietary fiber levels are found in Opuntia ficus-indica seeds [1, 2, 19]. The moisture level in O. ficus-indica fruit pulp is between 80 and 90% [16, 21].

3.1 Carbohydrates

In the pulp of O. ficus-indica fruit, glucose and fructose are the major monosaccharides, whereas glucose is the main monosaccharide in the fruit peel. As a result of the high invertase activities in O. ficus-indica fruits pulp, sucrose is converted to monosaccharides; therefore, sucrose is a minor sugar in O. ficus-indica fruits pulp. Besides the ethanol-soluble carbohydrates found in the peel and pulp, the amount of monosaccharides gives O. ficus-indica its sweet flavor [7, 8, 11, 16, 19, 22].

3.2 Fiber

Products made from O. ficus-indica are rich, edible fiber items for humans. O. ficus-indica seed has higher levels of fiber than fruit peel, making it a good source of fiber. Moreover, O. ficus-indica fruit peel and O. ficus-indica fruit seeds produced soluble and insoluble fibers [11, 16, 19].

According to Stintzing et al. [23], O. ficus-indica fruit pulp has an actual amount of pectin (about 70% of total fiber), but the fruit skin and seeds have cellulose concentrations of 71.0% and 83.0%, respectively. In O. ficus-indica fruit pulp, the raw fiber's concentration is 20 g/100 g db, with the primary fiber constituents being cellulose, hemicellulose, pectin, and lignin [16, 19, 24, 25]. The skin and seeds of O. ficus-indica fruit have higher amounts of cellulose than the pulp fiber, which is high in pectin [1, 2, 11, 16, 22].

3.3 Amino acids

Opuntia ficus-indica seeds contain a high protein level [16, 22]. As a result, O. ficus-indica pulp consists of proline, serine, and γ-aminobutyric acids (Table 1) as the primary amino acids [16, 18, 19, 23, 26]. The free amino acids in Opuntia ficus-indica contain all essential acids [16, 18, 23]. Besides, the free amino acids found in O. ficus-indica pulp predominate glutamine, proline, and taurine [16, 19].

Table 1 Amino acid levels in Opuntia ficus-indica
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The main amino acids in Opuntia ficus-indica seeds are glutamic acid (20.0 g/100 g protein) and arginine acid (14.0 g/100 g protein) [11, 27]. Moreover, in the pulp of different O. ficus-indica cultivars, the primary amino acids are taurine (semi-essential amino acids), glutamine and proline [16, 18, 21, 23]. As a cellular protective amino acid, taurine has a purpose. Moreover, taurine is regarded as a cell membrane stabilizer, providing osmoregulation, hypercholesterolemia, neuromodulation, and a preventative agent for fatty liver disease and hepatic steatosis. Moreover, taurine is an antioxidant and modifies the inflammatory response [16, 19, 29].

3.4 Fatty acids profile

Both polyunsaturated (PUFA) and monounsaturated (MUFA) fatty acids have positive health effects and enhance the health of many disorders, including cardiovascular diseases, obesity, diabetes mellitus (DM), and several types of cancer. O. ficus-indica fruit pulp and peel are rich sources of MUFA and PUFA. Fruit pulp contains MUFA (17–40% of the total fatty acids) [1, 2, 16, 20]. Conversely, O. ficus-indica fruit peel has a lower MUFA (6.90–31.0%) but a higher PUFA (37–63%). In addition, O. ficus-indica seed oil contains a high level of PUFA (57.9–63.2%) and MUFA level (19.81–23.30%). In O. ficus-indica fruit peel, pulp, and seed oil, the plentiful fatty acids are oleic (C18:1), linoleic (C18:2), and palmitic (C16:0) acids [1, 2, 16, 20]. O. ficus-indica peel contains a higher level of linoleic acid than the fruit pulp (41.0 and 29.0%, respectively), while O. ficus-indica pulp has a higher level of oleic acid than the peel (27.0% in fruit pulp and 14.0% in fruit peel). Meanwhile, O. ficus-indica fruit pulp and peel have similar amounts of palmitic acid [1, 2, 16, 20, 29].

3.5 Vitamins

Vitamins are important active compounds in O. ficus-indica. The O. ficus-indica plant parts contain different levels of vitamins (Table 2). Ascorbic acid (vitamin C) levels in O. ficus-indica pulp range from 17.0 to 46.0 mg/100 g [16, 18, 19, 21, 23, 30]. Therefore, 250 mL O. ficus-indica juice could provide about 25% of the adults’ requirements if taken up 250 mL [19].

Table 2 Vitamins levels in O. ficus-indice
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Concerning lipid-soluble vitamins, vitamin E (α-tocopherol) is found in high quantity in O. ficus-indica peel (1761 mg/100 g lipids) [16, 18, 19, 21, 23]. Furthermore, α-tocopherol is found in the pulp of O. ficus-indica in greater concentrations than other vitamin E forms. Moreover, O. ficus-indica pulp oil contains a greater concentration of δ-tocopherol (442 mg/100 g lipids) than O. ficus-indica fruit seed oil. Also, O. ficus-indica fruit seed oil has a high level of γ-tocopherol (33 mg/100 g lipids). On the other side, vitamin K function is a cofactor in synthesizing the coagulation factors and the proteins of the bone matrix. Besides, high vitamin K levels are found in O. ficus-indica fruit seeds and pulp oils. Moreover, 150 μg of O. ficus-indica oil might meet vitamin K requirements [1, 2, 16, 19].

3.6 Minerals

The pulp of O. ficus-indica is regarded as a fruitful source of minerals [19], including potassium, calcium, sodium, and magnesium (Table 3). Aside from that, the amounts of magnesium and potassium in the green and orange pulp of O. ficus-indica are comparable [16, 31]. Phosphorus, potassium, magnesium, calcium, and sodium are abundant in O. ficus-indica fruit seeds [16, 18, 19, 22, 23]. O. ficus-indica juice has a higher calcium and magnesium content (around 59 mg and 98 mg per 100 g, respectively) than other juices, making it more helpful in preventing cramps and osteoporosis. High concentrations (mg/100g) of calcium (7517), sodium (1918), potassium (1684), and magnesium (1380) are reported in O. ficus-indica cladode [11, 16, 25].

Table 3 Mineral levels (mg/100g FW) in Opuntia ficus-indica plant parts
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4 Bioactive constituents in Opuntia spp. and their biological effects

A "bio-active compound" is a naturally occurring chemical that could interact with one or more constituents of living tissues to affect human health [32]. The coordinated and functional action of bioactive and nutraceutical compounds is the first step in establishing the positive benefits of foods on human health. Dietary components play a favorable influence in the expansion of food perception as functional and nutraceutical in addition to supplying essential nutrients. Because of this, it is important to keep track of how different compounds are distributed along the food chain and in different food groups.

Due to their richness of antioxidants, phenolic acids, and pigments, all Opuntia spp. parts (pulp, seeds, cladodes, roots, and juice) offer positive characteristics for human health. Meanwhile, due to Opuntia crassulacean-type acid metabolism, malic and citric acid concentrations increase in the evening.

Eucomic acid, isorhamnetin 3-O-rhamnoside-7-O-(rhamnosyl-hexoside), kaempferol 3-O-robinobioside-7-O-arabinofuranoside, and isorhamnetin 3-O-galactoside are the primary phenolics found in Opuntia plants [16, 33]. Those phenolic constituents provide Opuntia tissue with significant antioxidant activity [11, 16].

4.1 Phenolic compounds

Phenolics are the primary contributors to plant extract antioxidant traits. Their classification might benefit individuals significantly, primarily by encouraging their usage as healthy promoters. Various dietary phenolic compounds' health advantages are thought to be attributable to their antioxidant processes in treating chronic illnesses linked with oxidative damages. Meanwhile, Opuntia spp. plant parts are high in phenolic substances such as flavonoids and phenolic acids.

Isorhamnetin derivatives were the most abundant chemicals in O. ficus indica flowers. Similarly, isorhamnetin derivatives were plentiful in O. ficus-indica whole fruits. Isorhamnetin has anti-inflammatory properties, mostly due to its direct antioxidant effect in decreasing oxidative injury. In addition, isorhamnetin and isorhamnetin derivatives derived from O. ficus indica cladodes exhibited potent anti-inflammatory action via nitric oxide inhibition.

The natural antioxidant quercetin prevents lipid per-oxidation by chelating iron, inhibiting xanthine oxidase, and scavenging peroxy, hydroxyl, and superoxide radicals. The fruits and stem of O. ficus-indica were used to extract quercetin and its derivatives, including quercetin 3-methyl ether and dihydroquercetin. In addition to significantly reducing lipid peroxidation, the antioxidants quercetin, dihydroquercetin, and quercetin 3-methyl ether scavenged DPPH· free radicals. Quercetin 3-methyl ether has the most neuroprotective effect in cortical cell cultures against oxidative damage. In XO and DPPH· assays, dihydro quercetin (taxifolin) extracted from O. ficus indica fruit showed significant antioxidant activity Rhee et al. [34]. This bioactive compound was also efficient against microbiological and oxidative agents [35]. Furthermore, it showed high protection against alcohol oxidative stress in hepatocytes [16, 36].

The phenolic composition of O. ficus indica fruit seeds with high levels of feruloyl derivatives (350–940 g/g) was determined. Ferulic acid and ferulic acid derivatives have been extensively researched for their anti-inflammatory, diabetic, cancer, cardiovascular disease, and Alzheimer's disease effects [37]. Furthermore, ferulic acid outperformed its derivatives in terms of antioxidant capacity. Ferulic acid's high antioxidant activity, tightly related to its phenolic hydroxyl groups, quickly prevents radical chain reactions via a radical scavenging process. Furthermore, the therapeutic benefits of ferulic acid are explained by this molecule's capacity to interact with several cellular systems that might be concurrently and synergistically implicated in its biological action, such as signaling pathway modulation [16, 38].

Eucomic acid is the most abundant constituent in O. ficus indica cladodes, indicating its potential as an anti-aging development component. On the other side, piscidic acid (4073 mg/g) was the most abundant constituent in the fruit peels of O. ficus indica [39]. The fruit pulps of O. ficus-indica contain piscidic acid ranging from 381 to 470 mg/g [39]. Meanwhile, piscidic acid is a phenylpyruvic acid derivative identified as a potent iron chelator with antioxidant effects [16, 40].

Kaempferol, on the other hand, demonstrated intense antidepressant action by boosting -endorphin, that is an important physiological depression regulator [41]. Meanwhile, astragalin's anti-pneumonia efficacy was also explored [42]. In addition, opuntiol (6-hydroxymethyl-4-methoxy-2H-pyran-2-one) is an active chemical from Opuntia spp. that belongs to the flavonoid family. This chemical demonstrated a significant anti-inflammatory effect as a dual cyclooxygenase and lipoxygenase pathways inhibitor. It also reduced the levels of ROS and cytokines [16, 43]. Moreover, it recently demonstrated anti-proliferative activity in KB oral cancer cells via mitochondrial-dependent cell death via producing ROS. Furthermore, opuntiol substantially neutralized OH, O2, H2O2, and DPPH· radicals in a dose-dependent manner. In addition, opuntiol inhibited UV-induced oxidative stress related chemical alterations in the rat embryonic fibroblast cell (NIH-3T3) lines.

4.2 Flavonoids

The flavonoid concentration of O. ficus indica fruits was lower than the phenolic content because of the presence of phenolic acids and procyanidins [44]. However, some of their flavonoids are transformed into phenolic compounds as fruits ripen. Those metabolites are especially essential since they are anti-inflammatory, antioxidant, and anti-cancer agents [16]. Furthermore, antioxidants and a high quantity of stable pigment (betalain) in some cultivars' fruit pulp and fruit peel are among the benefits of producing Opuntia fruit [45]. Therefore, flavonoids isolated and discovered from cactus fruit have an excellent potential for use as medicinal agents [11, 16].

4.3 Betalains

Fruit from prickly pears is used by betalain to produce derivatives of betaxanthins and betacyanins. In comparison to the fruit pulp, the fruit peel contains more betalain. The total betalain values (92.0 mg/100 g fresh weight) have been recorded in the pulp of cactus pear fruit [46]. Betaxanthins and betacyanins produced from betalain are used as natural edible red and yellow colorants in food manufacturing. These have shown potential antioxidant efficacy. O. ficus indica has distinct phenolics that make it helpful in various uses, including nutrition, conventional drugs, and industrial uses. Meanwhile, betanin and indicaxanthin are similarly implicated in improved cell resilience to oxidative stress [11, 16].

4.4 Volatile compounds

Volatiles and aroma compounds affect fruit sensory quality. Their scents comprise a complex mixture of chemicals such as terpenes, ketones, aldehydes, alcohols, and esters. These substances are often found at low concentrations in fruits, and cultivar, climate circumstances, ripeness level, and storage conditions determine their variability. The concentration of these chemicals in O. ficus indica fruit pulp ranges from 3.33 mg/100g to 14.8 mg/100g [11, 16].

Even though O. ficus indica does not have a significant scent, up to 61 chemicals have been detected. Aldehydes and terpenes were the most abundant chemicals in the tested cultivars. The most prevalent substances were chemical groups and alcohols. Other research, however, found alcohols and esters to be the most frequent and abundant chemicals. 2,6-Nonadienal (vegetable notes), d-limonene (i.e., citrus notes), 2-hexenal (i.e., apple green, almond, sweet, and vegetable notes), nonanol (green, melon, and fatty qualities), and 1-hexanol (green and sweet notes) are some of the dominant chemicals. Although O. ficus indica fruits are widely recognized for their health-enhancing traits, a sensory investigation is required to fully understand the fruit scent and the cultivar's influence [11, 16].

5 Health benefits of Opuntia ingredients and bioactive compounds

Consuming unusual fruits high in phytochemicals that are good for your health may lengthen your life. Opuntia has a wide range of nutrients and bioactive chemicals with pharmacological effects (Tables 4 and 5), including minerals, lipids, vitamins, carbohydrates, proteins, and proteins with specific amino acids. These bioactive components have actions that include anti-inflammatory, anti-epileptogenic, anti-diabetic, anti-cancer, immunomodulatory, analgesic, cardiovascular support, hepatoprotective, gastroprotective, and nephroprotective [11, 16, 47]. Moreover, the high antioxidant amount brought on by the presence of betacyanin, phenolic compounds, betalain, and specific vitamins in high concentrations in Opuntia fruits is mainly responsible for the fruits' health-enhancing properties [48].

Table 4 Health benefits of Opuntia ficus-indica
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Table 5 Health benefit of Opuntia ficus-indica bioactive compounds
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5.1 Health-improving effects of insoluble dietary fiber

Dietary fiber intake exhibits several health benefits. In addition to decreasing bile acid levels in the human body, cellulose also reduces the excretion and/or production of several mutagens in feces. In response, lignin stimulates intestinal transit while decreasing fecal contents of 4-cholesterin-e-1 and secondary bile acids, increasing stool volume and having a higher potential to retain water. Also, hemicellulose hydrates the stool, encouraging frequent bowel movements [11, 16]. Due to its antioxidant phytochemicals and anti-diabetic and antihyperglycemic traits in an oxidative environment, Opuntia tissue functions as an inhibitor, preventing the onset of diabetes. Due to antioxidants, pigments, or phenolic acids, Opuntia spp. tissue has high technological uses and has been commonly used to treat several diseases, such as diabetes, obesity, cardiac, gastric, and inflammatory ulcers [11, 16].

5.2 Health-enhancing effects of soluble dietary fiber

The viscosity of the stomach's content is made more viscous by the soluble fiber; this property has been linked to delaying gastric emptying, decreased intestinal transit, a faster rate of starch breakdown, and a faster rate of glucose absorption. These physicochemical properties influence their therapeutic effects, such as solubility, viscosity, and fermentability [53]. In addition, they increase satiety, improve blood lipid concentrations, and improve glycemic response. Opuntia tissue has a high nutritious potential, primarily due to its dietary fiber, proteins, mineral, and phytochemical profiles. These effects result in modifications in blood cholesterol and glucose concentration [54, 55].

5.3 Impact on weight control

Comparing the Opuntia fiber pill to the placebo, it enhanced fecal fat excretion without causing any adverse effects. This observation may be caused by dietary fiber constituents such as gum, mucilage, and pectin fiber complex from O. ficus-indica, which could bind to lipids and produce a non-absorbable lipid-fibers complex that is eliminated by feces [49].

5.4 Effects on glucose reduction

The impact of O. ficus indica cladode in young volunteers post-exercise was reported. Meanwhile, from the placebo, O. ficus indica decreased glucose levels and raised serum insulin concentration [50]. Meanwhile, the cladode maturity stage and viscosity affect its anti-diabetic traits. Fiber (mainly pectin) is considered the reason for the hypoglycemic impact of the nopal may be due to its fiber content, mainly pectin [11].

5.5 Hepatoprotective effects

Opuntia ficus effects on hepatic steatosis consuming nopal significantly reduced hepatic triglyceride levels by about (50%), hepatomegaly, and biomarkers of hepatocyte injury in the obese Zucker murine model that mimics hepatic pathology of non-alcoholic fatty liver diseases. The decrease compared to the control is due to the impact of the nopal preventing cholesterol absorption. This fibre is broken down by the microbiota, which increases the presence of beneficial bacteria and produces CFA, an energy source for the colon cells. The leading cause of type 2 diabetes and heart diseases is oxidative stress because it hastens the formation of atherosclerotic arterial atherosclerosis consumption. The researchers hypothesized that dietary fiber and other bioactive nopal components might be involved. According to earlier studies, soluble fibers alter the production of hepatic lipids and increase intestinal permeability, which improves NAFLD biomarkers. Compared to the control, it is lower due to nopal consumption. The authors speculate that dietary fibre and other bioactive substances found in the nopal may also involve. Improved intestinal permeability and modified hepatic lipid production caused by soluble fibres improve NAFLD biomarkers [11, 21].

5.6 Antioxidant activities

The phenolics found in cactus pear fruit give them nutritional and medicinal benefits. Additionally, in lipid and aquatic media, prickly pear fruit extracts demonstrated effectiveness as a natural antioxidant [56]. The antioxidant potential of cactus fruits was estimated using a variety of antioxidant-dependent characteristic tests, such as the reactivity against radicals and the localization, distribution, and fate of antioxidant-derived radicals in conjunction with other antioxidant compounds [11, 16, 56].

Oxidative stress is involved in many human illnesses. As antioxidants, bioactive molecules serve a critical function. They are the essential plant antioxidant sources for decreasing oxidative stress-induced tissue damage caused by chronic illnesses. For generations, Opuntia sp. has been used as an edible source and a conventional drug to treat various chronic conditions, including obesity, inflammatory and cardiovascular disorders, diabetes, and stomach ulcers. In addition, they are also employed in the agricultural, cosmetic, culinary, and wastewater treatment sectors. Meanwhile, carotenoids, coumarins, flavonoids, vitamins, pectin, and other beneficial substances are found in Opuntia spp [11, 16].

5.7 Anticancer activity

Cactus pear fruit extract showed a growth inhibition effect on several human cancer cell lines, including those of bladder, ovarian, and cervical cancer cell lines. Meanwhile, extracts may stop tumor growth in the in vivo-nude mice ovarian cancer animal model. More significantly, similar to the synthetic retinoid N-(4-hydroxyphenyl) retinamide, a chemopreventive medication utilized to treat ovarian cancer, tumor growth suppression was seen [57]. Three separate human cancer cell types-ovarian, bladder and cervical-were all shown to be sensitive to the cactus pear extracts' anticancer properties. Cells from bladder and ovarian cancers were less responsive in this investigation than cervical cancer cells. They discovered that 40–60% of cervical cancer cells were suppressed by 1% cactus pear fruit extract [58].

5.8 Antiviral effect

Cactus fruit extract prevented the intra- and extra-cellular reproduction of a specific DNA and RNA virus when given to mice, horses, and people. In addition, it was discovered that the cactus extract stopped the Herpes Simplex Virus type 2 in horses, the pseudorabies virus, the influenza virus, the respiratory syncytial illness virus, and HIV-1. However, the cactus extract's mechanism of action and active inhibitory component(s) have not been investigated [51].

5.9 Antiinflammatory effect

Betanin and betaxanthin inhibited myeloperoxidase's chlorination activity in cactus pear fruit at neutral pH rather than at pH 5 [11, 59]. Cactus pear's specific compounds make it valuable in various fields, including clinical nutrition, traditional drugs, and other industrial uses. The primary components in the health benefits and medicinal action are the betanin content, betaxanthin, indicaxanthin, and betacyanin, strengthening the cells' resistance to induce oxidative [11, 16].

5.10 Antimicrobial potential

Essential oils have been extensively researched as natural antimicrobial agents with potential use instead of chemical ones. Meanwhile, essential oils have a potent antimicrobial impact on various bacteria, including foodborne pathogens, postharvest pathogens and spoilage microorganisms [52]. For example, applying the disc-diffusion test, the Opuntia stricta fruit essential oil displayed an antimicrobial effect against gram-positive bacteria (Escherichia coli, Bacillus licheniformis, Pseudomonas aeruginosa, and Bacillus cereus) and Candida albicans at 20–40 mg/mL concentrations [60].

6 Potential applications of O. ficus-indica

6.1 Food applications

Numerous dietary and value-added edible products have been employed as nutritious ingredients. It is a great natural energy source because both fruits and stems could be eaten, together with the nutritional elements and antioxidants that can be added as an edible supplement [16, 61].

Opuntia ficus indica are professionally farmed for both edible and feed applications. It has nutrients and bioactive chemicals with pharmacological effects, including minerals, carbohydrates, lipids, vitamins, proteins, and protein with certain amino acids. The Opuntia fruit is made up of a thick skin (40–60%) that surrounds a juicy pulp (ca. 60%) with several seeds (3–10% fruit fresh weight) [7, 8, 11].

Opuntia seed oil is usually used in various meals, cosmetics, and pharmaceuticals, but fruit seeds have a significant lipid content. Some Opuntia fruits include large concentrations of natural pigments that can be used as food coloring, such as yellow to orange betaxanthins and red to violet betacyanins. Additionally, Opuntia fruits have a significant quantity of distinctive plant mucilage, which acts as a thickener agent. Most Opuntia fruits, including O. ficus-indica fruits, have low acidity, making them perfect for combining with various dairy products. Opuntia is necessary for creating functional and unique foods due to its readily absorbed sugars, high vitamin C, mineral, and phenolic chemical concentrations, and pleasant flavor [3,4,5,6,7,8].

Because of their health-related solid properties and functional features, Opuntia fruits may be effectively used in various food processing applications. Bioactive chemicals such as polyphenolic constituents, vitamin C, betalain, and β-carotene are abundant in juices and nectars. The amounts of fruit pulp (ca. 15–75%), citric acid (ca. 0.3%), sugar, and water in these products vary [21].

Thermal treatment is one of the culinary technologies used to improve the shelf life of Opuntia goods. Heat and thermal treatments may result in the breakdown of some thermolabile compounds and a change in the organoleptic properties. As a result, in the retention (or release) of bioactive chemicals. However, on the other hand, the great amount of products created during Opuntia fruit processing might still be used as a source of active components [3,4,5,6,7].

6.2 Traditional medicinal applications

It has been applied in traditional folk medicine, particularly for the treatments of wound healing, chronic diseases (i.e., obesity, diabetes, cardiovascular diseases, and cancers), and urinary tract infections due to the chemical constituents that Opuntia tissue has and the biological effects (i.e., hypoglycemic, antioxidant, antimicrobial, inflammatory, and neuroprotective traits) [62, 63].

Additionally, O. ficus-indica is a species employed in traditional medicine to treat sickness. Because the pharmaceutical agents found in those plants, which might be employed in creating value-added goods, revised the chemistry, pharmacology, pharmacognosy, and functional applications, they have been used to treat numerous ailments. A protective impact may also be produced by biological processes that are antiviral, antiulcer, neuroprotective, anti-inflammatory, anti-diabetic, hepatoprotective, anticancer, antibacterial, alcohol hangover, and antioxidant [64]. According to Santos-Daz et al. [62], the phytochemicals, biopeptides, and soluble fibres in Opuntia spp. have therapeutic traits that may help prevent type 2 diabetes and other chronic diseases.

6.3 Other applications

Opuntia plants have different uses that could boost the incomes of those who reside in semi-arid and dry regions [16, 65]. For instance, Opuntia plants could be used for the production of beverages [63], as a source of dyes, in the cosmetics, and as natural fences [66], as well as for the decontamination of wastewater, the production of candies [63], the protection of buildings, and for soil conservation [67]. However, the crop production commonly used as cattle forage or fodder is either uneconomical or unsustainable in semi-arid and arid locations where water supply is constrained [68,69,70]. Meanwhile, using cactus as calf feed is cost-effective [11, 16, 66].

7 Conclusion

The lifespan of consumers may increase if they consume non-traditional fruits rich in health-promoting compounds. Opuntia plants are typically found in the world's dry and semi-arid climates. The FAO recommended Opuntia spp. as a promising and strategic crop in various countries, particularly those that experience a lack of water, to combat global climate change. Opuntia's ecological advantages enable CO2 uptake at night, reducing water loss during photosynthesis. In various places of the world, several Opuntia species are known as renowned weeds, and some species, including Opuntia ficus indica, are professionally grown for use in food and feed. The current review of Opuntia spp. covers emphasis on the chemistry, functionality, and usability of Opuntia fruits, extracts, and biowastes. It also discusses the composition of Opuntia spp. The information given in this work is crucial for nutraceuticals, pharmaceuticals, novel food, and traditional food developers.