Journal of Natural Medicines

, Volume 62, Issue 2, pp 195–198

Oligostilbenoids from Shorea gibbosa and their cytotoxic properties against P-388 cells

Authors

  • Haryoto Saroyobudiono
    • Natural Products Research Group, Department of ChemistryBandung Institute of Technology
  • Lia D. Juliawaty
    • Natural Products Research Group, Department of ChemistryBandung Institute of Technology
  • Yana M. Syah
    • Natural Products Research Group, Department of ChemistryBandung Institute of Technology
  • Sjamsul A. Achmad
    • Natural Products Research Group, Department of ChemistryBandung Institute of Technology
    • Natural Products Research Group, Department of ChemistryBandung Institute of Technology
  • Jalifah Latip
    • School of Chemistry and Food Technology, Faculty of Science and TechnologyNational University of Malaysia
  • Ikram M. Said
    • School of Chemistry and Food Technology, Faculty of Science and TechnologyNational University of Malaysia
Note

DOI: 10.1007/s11418-007-0205-0

Cite this article as:
Saroyobudiono, H., Juliawaty, L.D., Syah, Y.M. et al. J Nat Med (2008) 62: 195. doi:10.1007/s11418-007-0205-0

Abstract

A new oligostilbenoid derivative, diptoindonesin F (1), along with five known oligostilbenoids, (−)-ampelopsin A (2), (−)-α-viniferin (3), ampelopsin E (4), (−)-vaticanol B (5), and (−)-hemsleyanol D (6), were isolated from the methanol extract of the tree bark of Shorea gibbosa. The structure of the new compound was determined based on the analysis of spectroscopic data, including UV, IR, NMR 1-D and 2-D, and mass spectra. Cytotoxic properties of the isolated oligostilbenoids were evaluated against murine leukemia P-388 cells with the result that compounds 2 and 4 showed the highest cytotoxicity.

Keywords

Diptoindonesin FOligostilbenoidShorea gibbosaDipterocarpaceaeCytotoxicityP-388 cells

Introduction

The plants belonging to the family Dipterocarpaceae have been known to produce oligostilbenoid compounds [13]. They include di-, tri-, tetra-, hexa-, hepta-, and octastilbenoids, containing various molecular frameworks as a result of different condensation of the resveratrol monomer. Some of these compounds show interesting biological activities, such as antibacterial, antiviral, and cytotoxic effects [2, 3]. In previous papers, we had reported a number of oligostilbenoid compounds, including five new compounds, as well as their cytotoxic properties against murine leukemia P-388 cells [47]. As part of our study on the phytochemistry and biological activities of the oligostilbenoids from Indonesian dipterocarpaceous plants, we now report the isolation of a new C-glucoside derivative of a tetrastilbene, trivially named diptoindonesin F (1) (Fig. 1), from the tree bark of Shorea gibbosa Brandis, along with five known oligostilbenoids, (−)-ampelopsin A (2) [8], (−)-α-viniferin (3) [9], ampelopsin E (4) [10], (−)-vaticanol B (5) [11], and (−)-hemsleyanol D (6) [12]. The cytotoxic properties of the isolated compounds against P-388 cells are also described.
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Fig. 1

Structure of diptoindonesin F (1) isolated from Shorea gibbosa

Results and discussion

Diptoindonesin F (1), isolated as a brownish yellow solid, showed a positive [M + Na]+ ion in the high resolution ESIMS at m/z 1091.3062, corresponding to a molecular formula C62H52O17 (calc. for C62H52O17Na 1091.3102). The UV sprectrum of 1 showed maxima (λmax 204, 231, and 283 nm) typical for an oligostilbene containing only the chromophore of substituted phenol, and the IR spectrum exhibited absorptions for hydroxyl (3,400 cm−1), alkyl (2,927 cm−1), and aromatic (1,614 and 1,512 cm−1) groups. Consistent with the molecular formula, the 13C NMR (APT, Attached Proton Test) spectrum of 1 showed 50 carbon signals representing 62 atom carbons and are distributed into 12 oxyaryl, 13 quarternary aromatic, 23 methine aromatic, 13 methine alkyl, and 1 methylene alkyl carbons. Of these alkyl carbon signals, six of them, i.e., the signals at δC 61.9, 70.8, 74.0, 77.4, 78.5, and 81.6, were characteristic for a β-C-glucopyranosyl carbons [4]. Thus, these spectroscopic data suggested that 1 is a glucoside derivative of a tetrastilbene. In the 1H NMR spectrum of 1 (Table 1), coupled with 1H−1H COSY spectrum, a number of aromatic signals was observed, and these can be assigned to four p-hydroxyphenyl (δH 7.17, 7.15, 6.91, 6.89, 6.79, 6.78, 6.57, and 6.56), three 2-substituted-3,5-dihydroxyphenyl (δH 6.54, 6.52, 6.38, 6.33, 5.86, and 5.12), and one 2,4-disubstituted-3,5-dihydroxyphenyl (δH 5.09) groups. The 1H NMR spectrum also showed two pairs of doublet signals (δH 5.87 and 4.26, 5.77 and 4.25, each J = 11.5 Hz) characteristic for the methine protons of two 1,2-diaryldihydrobenzofuran moieties, as well as four methine proton signals for a CH–CH–CH–CH unit (δH 5.85, 5.86, 3.85, and 3.83) and a number of other alkyl proton signals at δH 4.42 as a doublet (J = 9.0 Hz) and δH 4.5–3.2 assignable to a C-glucosyl unit. In addition, eight proton singlets for ten phenolic hydroxyl groups were also shown in the 1H NMR spectrum (see Table 1). Excluding the signals of the C-glucosyl group, these 1H NMR data are very similar to those of (−)-hopeaphenol [13], and by comparison the attachment of the glucosyl group could be either at C-12b or C-14b. HMQC and HMBC measurements, therefore, were used to determine the exact position of the glucosyl group. The HMBC spectrum of 1, in particular, revealed 1H-13C long range correlations between the aromatic singlet proton at δH 5.09 with carbon signals at δC 48.3 (C-8b) and 155.7 (C-13b), indicating that C-14b is unsubstituted and consequently the glucosyl group is attached to C-12b. This conclusion is corroborated by the observation that the carbon signal of C-13b (δC 155.7) also showed a long range correlation with the anomeric proton signal of the glucosyl moiety at δH 4.42 (H-1′). From these HMBC correlations, the position of the glucosyl group was unambiguously established at C-12b. Other HMBC correlations in support of structure 1 for diptoindonesin F are summarized in Fig. 2. The relative stereochemistry at the chiral carbons in the oligostilbenoid part was determined from the NOE correlations found in the ROESY spectrum. The presence of NOE correlations among H-7a and H-13a, H-8b and H-2b/6b, H-8c and H-2c/6c, and H-7d and H-13d, established trans relationships for H-7a/H-8a, H-7b/H-8b, H7-c/H-8c, and H-7d/H-8d. The spatial relation between H-8a and the ring B1, and also between H-8d and the ring C1, was deduced to be cis as indicated by the chemical shifts of H-8a and H-8d (δH 4.26 and 4.25, respectively), which experience shielding effects from the respective rings B1 and C1 [14]. These sterochemical characteristics are again identical to those of (−)-hopeaphenol. Consequently, diptoindonesin F (1) was established as (−)-hopeaphenol-12b-C-β-glucopyranoside. At this stage, the absolute stereochemistry of 1 could not be determined.
Table 1

NMR data (d6-acetone) of compound 1

No.

δH (mult., J in Hz)

δC

No

δH (mult., J in Hz)

δC

1a

131.0

1c

134.9

2a/6a

7.17 (d, 8.5)

130.3

2c/6c

6.91 (d, 8.5)

129.2

3a/5a

6.79 (d, 8.5)

116.0

3c/5c

6.57 (d, 8.5)

115.2

4a

158.5

4c

155.6

7a

5.87 (d, 11.5)

88.8

7c

5.85 (d, 4.5)

40.8

8a

4.26 (d, 11.5)

50.4

8c

3.83 (dd, 7.7, 4.5)

48.4

9a

142.1

9c

140.7

10a

120.9

10c

119.3

11a

158.9

11c

159.2

12a

6.52 (d, 1.9)

101.1

12c

5.86 (d, 2.5)

95.3

13a

157.3

13c

155.9

14a

6.38 (br s)

106.3

14c

5.12 (d, 2.5)

111.5

1b

135.0

1d

130.8

2b/6b

6.89 (d, 8.5)

129.2

2d/6d

7.15 (d, 8.5)

130.2

3b/5b

6.56 (d, 8.5)

115.2

3d/5d

6.78 (d, 8.5)

116.0

4b

155.6

4d

158.5

7b

5.86 (d, 4.5)

40.8

7d

5.77 (d, 11.5)

88.5

8b

3.85 (dd, 7.7, 4.5)

48.4

8d

4.25 (d, 11.5)

49.6

9b

140.7

9d

142.3

10b

118.2

10d

120.9

11b

157.0

11d

158.9

12b

104.1

12d

6.54 (d, 2.4)

101.1

13b

155.7

13d

157.3

14b

5.09 (s)

112.7

14d

6.33 (br s)

106.1

4a-OH

8.62 (s)

 

1′

4.42 (d, 9.0)

77.4

11a-OH

8.61 (s)

 

2′

3.42 (m)

74.1

13a-OH

8.34 (s)

 

3′

3.44 (m)

78.5

4b-OH

8.13 (s)

 

4′

3.49 (m)

70.8

13b-OH

7.24 (s)

 

5′

3.31 (m)

81.8

4c-OH

8.11 (s)

 

6′a/6′b

3.74 (m)

61.9

13c-OH

8.22 (s)

    

4d-OH

8.64 (s)

    

11d-OH

8.58 (s)

    

13d-OH

8.34 (s)

    
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Fig. 2

HMBC correlations (1H ↔ 13C) in compound 1

The presence of compound 1 in S. gibbosa is the first example of a C-glucoside derivative of a tetrastilbene in Dipterocarpaceous plants. Previous phytochemical works disclosed a number of C-glucoside derivatives of dimer- and trimerstilbenes from S. hemsleyana [12, 15] and S. seminis [4]. Thus, the presence of these C-glucoside derivatives in some species of Shorea could be one of important chemical characters for the chemotaxonomical analysis of the genus.

Cytotoxic properties of compounds 3 and 5 against P-388 cells have been described in a previous paper [7]; their IC50 values were 25.7 ± 1.5 and 46.4 ± 1.5 μM, respectively. On cytotoxic evaluation compared to the same tumor cells, compounds 1, 2, 4, and 6 exhibited IC50 values of 34.6 ± 3.3, 17.0 ± 1.5, 15.3 ± 0.3, and 94.7 ± 1.5 μM, respectively. It is worth noting that the cytotoxic effect of compound 1 is almost one sixth of those of (−)-hopeaphenol (IC50 5.2 ± 0.3 μM) [7], indicating that C-glucosylation of the oligostilbenoid and hence the increasing polarity of the molecule greatly reduce the cytotoxic effect of the oligostilbenoid. In addition, these cytotoxic data also suggested that no regular pattern is observed between molecular size and cytotoxic properties of the oligostilbenoids. However, in general observation, a smaller size of the oligostilbenoid tends to be more cytotoxic than the larger one, as can be seen by comparison of the cytotoxic properties of compounds 24 with the compounds 5 and 6.

Experimental

General experimental procedures

The UV and IR spectra were measured with Varian 100 Conc and FTIR Spectrum One Perkin-Elmer instruments, respectively. 1H and 13C NMR spectra were recorded with a JEOL ECP400 spectrometer operating at 400 (1H) and 100 (13C) MHz, using residual and deuterated solvent peaks as reference standards. MS spectra were obtained with a LCTOF JMS-T100LC (ESI mode, direct probe). Vacuum liquid chromatography (VLC) and radial chromatography were carried out using Merck Si gel 60 GF254 and, for TLC analysis, precoated Si gel plates (Merck Kieselgel 60 GF254, 0.25 mm) were used.

Plant material

Sample of the tree bark of S. gibbosa was collected from the plant garden of PT Aya Yayang Indonesia, Camp 63, Tanjung, Tabalong, South Kalimantan, Indonesia. The identity of the plant was determined by a staff of the Herbarium Bogoriense, Bogor, Indonesia.

Extraction and isolation

The dried and powdered tree bark (2.5 kg) of S. gibbosa was macerated with acetone (10 l × 3), and the acetone extract was evaporated under reduced pressure to give a dark brown residue (95 g). The dried acetone extract was dissolved in a small volume of MeOH (≈200 ml), diluted with diethyl ether to a volume ≈2 l to give a MeOH-diethyl ether soluble fraction (65 g) after decantation and evaporation. Part of the fraction (55 g) was subjected to vacuum liquid chromatography [silica gel, 250 g; eluted with mixtures of n-hexane–ethyl acetate (7:3, 3:2, and 1:1), EtOAc, and EtOAc–MeOH (19:1)] to give five major fractions A-E. Fraction D (1.5 g) was refractionated with radial chromatography [silica gel, eluted with n-hexane-ethyl acetate (9:1–7:3)] to give four fractions D1–D4 (each 115, 170, 190 mg, and 1.12 g, respectively). On chromatographic separation of fraction D4 using Sephadex LH-20 the column (MeOH elution) yielded a fraction (130 mg) rich with compound 1. Repeated purification (2x) of this faction with the radial chromatography technique (silica gel, eluted with CHCl3–MeOH = 9:1–3:1) gave compound 1 (30 mg). Using the same methodology, fraction B yielded compounds 2 (20 mg) and 3 (25 mg), while from fraction C compounds 4–6 were purified (5, 70, and 35 mg, respectively).

Cytotoxic evaluation

Cytotoxic properties of the isolated compounds 16 against murine leukemia P-388 cells was evaluated according to the method of MTT assay as previously described [6, 7].

Diptoindonesin F (1)

Brownish yellow solid. [α]20D = −196° (c 0.1, MeOH); UV (MeOH) λmax nm (log ε): 204 (4.89), 231 (4.65), 283 (4.14); (MeOH + NaOH) 206 (5.06), 250 (4.42), 298 (4.12); IR (KBr) νmax cm−1: 3,400, 2,927, 1,614, 1,512, 1,443, 1,342, 1,174, 1,147, 1,084, 1,011, 835; 1H NMR (d6-acetone) see Table 1; 13C NMR (d6-acetone) see Table 1; HRESI-MS m/z: [M + Na]+ 1,091.3062 (calcd. for C62H52O17Na: 1,091.3102).

Acknowledgments

We thank Dr. H. Karasawa and Dr. A. Kusai from JEOL, Japan, for mass spectra measurements. We also thank the Herbarium Bogoriense, Bogor, Indonesia, for identification of the plant specimen.

Copyright information

© The Japanese Society of Pharmacognosy and Springer 2007