|Year : 2013 | Volume
| Issue : 1 | Page : 90-94
Chemical constituents from the aerial parts of Salsola inermis
Fatma S. Elsharabasy1, Ahlam M. Hosney2
1 Department of Chemistry of Natural and Microbial Products, National Research Center, Dokki, Egypt; Collage of Science and Humanities, Salman bin Abdul Aziz University, Alkharj City, Kingdom of Saudi Arabia
2 Department of Theraputic Chemistry, National Research Center, Dokki, Egypt
|Date of Submission||22-Jul-2012|
|Date of Acceptance||31-Oct-2012|
|Date of Web Publication||18-Jul-2014|
Fatma S. Elsharabasy
PhD, Department of Chemistry of Natural and Microbial Products, National Research Center, El-Behooth St, Dokki 12311, Egypt
Source of Support: None, Conflict of Interest: None
Background and objective
The hydroalcoholic extract from the aerial parts of Salsola inermis exhibited antioxidant, anti-inflammatory, and antinociceptive effects. The present study deals with the isolation and identification of the chemical constituents of this hydroalcoholic extract.
Materials and methods
The aerial parts of S. inermis (Forsskal) were collected from wild plants growing near the El-Alamein area in October 2005. Air-dried and powdered aerial parts of S. inermis were extracted with 70% alcohol in H2O. The extract was partitioned successively with CHCl3, EtOAc, and n-BuOH. The structures of the isolated compounds were determined by chemical and spectroscopic analyses.
Results and conclusion
Phytochemical investigation of the alcoholic extract from the aerial parts of S. inermis revealed 12 compounds, identified as long chain hydroxyl fatty acid 9,12,13-trihydroxydecosan–10,15,19-trienoic acid; trans-N-feruloyl tyramine-4ººº-O-β-D-glucopyranoside; umbelliferone; scopoletin; 3-methyl kaempferol; olean-12-en-3,28-diol; olean-12-en-28-oic acid; stigmasterol-3-β-O-D-glucopyranoside; 3-O-[β-D-glucopyranosyl]oleanolic acid; kaempferol 3-O-β-glucopyranoside; and isorhamnetin 3-O-β-glucopyranoside, in addition to β-sitosterol, stigmasterol, and stigmastanol.
Some of these compounds have hydroxyl groups, which help in scavenging free radicals and inhibit COX and various mediators involved in the pathogenesis of pain relief.
Keywords: aerial parts, coumarins, flavonoids, NMR, Salsola inermis, terpenes
|How to cite this article:|
Elsharabasy FS, Hosney AM. Chemical constituents from the aerial parts of Salsola inermis. Egypt Pharmaceut J 2013;12:90-4
| Introduction|| |
The genus Salsola, family Chenopodiaceae (Goosefoot family), includes over 100 species found in the dry regions of Asia, Europe, and Africa 1. The Salsola species represents 16 species in Egypt, most of which grow in the Egyptian deserts 2. Previous phytochemical investigation of the genus resulted in the isolation of alkaloids, saponins, sterols and their glucosides, comarino-lignan, isoflavonoids, and flavonoids 3–10. Some Salsola plants are widely used as folk medicine for the treatment of hepatitis 11 or infections caused by tapeworm and parasites 12; they also have pronounced vasoconstrictive, hypertensive, and cardiac stimulant action 13 and can act as an allergenic substance 14,15. Reactive oxygen species (ROS) are always present in cells as metabolic products of normal cellular respiration. However, oxidative stress, an imbalance caused by excessive ROS originating from endogenous and exogenous sources, might cause inflammation and therefore play a pivotal role in many diseases 16. Cytopreventive antioxidants prevent the formation of free radicals and scavenge them or promote their decomposition 17. In chemical terms, polyhydroxy flavonoids efficiently modulate the redox status and thus may play a critical role in regulating the inducible gene expression of inflammatory mediators in the lipopolysaccharide-stimulated mouse leukemic monocyte macrophage cell line (RAW 2647macrophages) 18.
As a continuation of our previous studies that showed that the ethanol extract of Salsola inermis has antioxidant and anti-inflammatory properties 19, the present study deals with the isolation and identification of chemical constituents of the hydroalcoholic extract from the aerial parts of S. inermis.
| Materials and methods|| |
Electron impact mass spectra (EIMS) were obtained using Varian MAT 711 (Germany), Finnigan SSQ 7000 (San Jose, California, USA), and OMM 7070 E spectrometers (Maryland, USA). 1H-NMR and 13C-NMR spectra were recorded at 500 MHz on a JEOL 500 A spectrometer (JEOL Inc., USA). The 1H-NMR and 13C-NMR chemical shifts are expressed in ppm relative to tetramethylsilane. Infrared (IR) spectra were measured on a Perkin Elmer FT-IR1700 spectrometer (Perkin Elmer, USA) at the National Research Centre, Cairo, Egypt. Ultraviolet (UV) spectra were recorded on a Shimadzu UV-Vis spectrophotometer (Shimadzu, USA). Thin layer chromatography (TLC) plates (aluminum sheets) precoated with silica gel G 60 (F 254; Merck) were used for chromatography. Special reagents used were iodine–potassium iodide for detection of coumarins and chlorosulfonic acid spray reagent for the detection of sterols and triterpens. The two-dimensional paper chromatographic technique using the solvent system BuOH : HOAc : H2O (4 : 1 : 5) and HOAc (15%) was also used 20.
The aerial parts of S. inermis (Forsskal) were collected from wild plants growing near the El-Alamein area in October 2005. The plant specimen was authenticated by Dr N. El-Hadidi, Faculty of Science, Cairo University, and was compared with reference herbarium specimens.
General procedure for extraction and isolation
Air-dried and powdered aerial parts of S. inermis were extracted with 70% alcohol in H2O after evaporation of the solvent under reduced pressure. It was essential that the extract (200 g) be partitioned successively with CHCl3, EtOAc, and n-BuOH.
The CHCl3 fraction (8 g) was applied onto a silica gel column and eluted with a gradient of n-hexane, CHCl3, and MeOH (100–0, 90–10, 80–20, 70–30, 60–40, 50–50, 40–60, 20–80, 0–100) to give five fractions A1–A5. Further purification of A1 (0.8 g) by preparative TLC with n-hexane/CHCl3 as an eluent afforded compounds I (0.05 g) and II (0.02 g). Moreover, column chromatography of A2 with CHCl3 afforded compounds III (0.28 g) and IV (0.10 g). Column chromatography of A4 with gradient elution using EtOAc/MeOH yielded compound V (0.18 g). The EtOAc fraction (7 g) was chromatographed over silica gel with successive petroleum ether/EtOAc (80–20, 20–80, 0–100) and EtOAc/MeOH (90–10, 0–100) elution to give eight fractions, B1–B8. Column chromatography of B6 (1.24 g) with CHCl3/MeOH elution (9–1 and 9–2) afforded compounds VI (5 mg) and VII (3 mg). Further, column chromatography of B8 with CHCl3/MeOH elution (9–1 and 8–2) afforded compound VIII (6 mg). BuOH (12 g) applied onto a flash column chromatography column with H2O/MeOH gradient elution afforded three fractions, C1–C3. Purification of C2 and C3 carried out on a Sephadex LH-20 column with CHCl3/MeOH elution (1–9 and 0–10) afforded compounds IX, X, XI, and XII. The physical and spectral data of the isolated compounds are as follows.
Gummy white solid, EIMS, m/z 386: [M]+ calculated for C22H42O5; IR (KBr) &ngr;max cm−1 3437, 2925, 2854, 1740, 929; 1H-NMR (500 MHz, CDCl3) δH 0.9 (3H, t, J=7.3, H-22), 1.35 (11 H, bs, H-4, H-5, H-6, H-7, H-8a), 1.45 (1H, m, H-8b), 1.61 (2H, m, H-3), 2.05 (2H, t, J=6, 8 Hz, H-21), 2.17 (1H, m, H-14a), 2.33 (1H, m, H-14b), 3.46 (1H, m, H-13), 3.98 (1H, t, J=5.3 Hz, H-12), 4.05 (1H, m, H-9), 5.42, O, (1H, J=11.2, 5.2 Hz, H-16), 5.47, O, (1H, J=11.2, 5.2 Hz, H-15), 5.68 (1H, dd, J=15.7, 5.2 Hz, H-11), 5.73 (1H, dd, J=15.7, 5.2 Hz, H-10).
Amorphous powder, IR (KBr) &ngr;max cm−1 3416, 2925, 1725, 1646, 1515, 1269, 1074. EIMS, m/z: 476 [M]+calcd for C24H30NO9. UV λmax (MeOH) nm (loge): 225 (3.12), 278 (2.99), 311 (3.1). 1H-NMR and 13C-NMR spectral data are presented in [Table 1].
|Table 1: 1H-NMR (300 MHz) and 13C-NMR (300 MHz) for compound II (CHCl3-d6)|
Click here to view
White crystals, m.p. 225–228°C, Rf 0.42 (TLC, S1); UV λmax nm (MeOH) 217, 245, 260sh, 279sh, and 322 nm; EIMS m/z 162 [M]+, C9H6O3. 1H-NMR (500 MHz, CDCl3) δH 6.15 (1H, d, J=9.6 Hz, H-3), 6.58 (1H, d, J=2.6 Hz, H-8), 6.85 (1H, dd, J=8.6 Hz, H-6), 7.35 (1H, d, J=8.6 Hz, H-5), 7.81 (1H, d, J=9.3 Hz, H-4).
Colorless needle crystals (CHCl3), m.p. 221–223°C, Rf 0.5 (TLC, S1); UV λmax nm (MeOH) 229, 250sh, 260sh, 295sh and 342 nm. 1H-NMR (500 MHz, CDCl3) δH 6.26 and 7.58 (2H, d, J=9.6 Hz, H-3 and H-4), 6.85 and 6.92 (2H, s, H-8 and H-5) and 3.92 (3H, s, Me-6).
Colorless needles, m.p. 131–132°C, showed [M+] peak at m/z 412 (25.0%), 414 (17%), and 416 (1.40%) and characteristic fragmentation peaks at m/z 275, 255, 231, 213.
White needles (0.22 g), m.p. 254°C. M+ peak at m/z 441 (9.30%), corresponding to C30H50O, and an intensive peak at m/z 411 (18.92%), corresponding to M+–CH2OH. IR showed characteristic absorption bands at 3395 (OH), 2925 cyclic (CH2), 1730, and 1446 (C=C). D12 double bond proved to be readily recognizable by mass spectra and 1H-NMR shows seven tertiary methyl proton singlets at 0.81, 0.82, 0.84, 0.86, 1.18, 1.22, and 1.84, an olefin proton at δ 5.4 (br.s.), and a hydroxyl methylene proton at 5.14.
Isolated as white crystals (0.01 g), m.p. 259–60°C, IR spectrum showed strong bands near 3415 cm−1 (OH), 1735 cm−1 (CO), two bands 1390–1375 and 1369–1354 cm−1 in the ‘A-region’, and three bands at 1328–1318, 1303–1296, and 1267–1248 cm−1 in the ‘β-region’; its mass gave an M++1 peak at m/z 457 (2.02%), corresponding to C30H48O3, fragmentation characteristic with respect to oleanane triterpenoids having D12 : 13 unsaturation. The ion at m/z 189 stands for rings A and B in the dehydrated form 21.
Yellow powder, m.p. 275–278°C, Rf 0.47 (TLC, S2); UV λmax nm (MeOH) 268 and 363, (MeOH/NaOMe) 279 and 423, (MeOH/AlCl3) 269 and 423; 1H-NMR (500 MHz, DMSO) δH 6.16 and 6.42 (2H, d, J=2.2 Hz, H-6 and H-8), 6.90 and 8.0 (each 2H, d, J=8.7 Hz, H-3º, -5º and H-2º,-6º).
White powder, m.p. 265–268°C, Rf 0.47 (TLC, S2); EIMS, M+ peak at m/z 576, 9.45%, corresponding to the molecular formula C35H60O6, m/z 163 (13.54) of one hexose sugar; IR spectrum (KBr) Vmax cm−1, 3421 (OH), 1730–1446 (C=C), 1129, 1076, 1055, and 1015 (ether linkage of glycoside); 1H-NMR (500 MHz, DMSO-d6) δH 0.64 and 1.02 (each 3H, s, H-18 and H-19), 0.78–0.85 (9H, m, H-26, 27 and H-29), 0.89 (3H, d, J=6.6 Hz, H-21), 0.94 (3H, m, H-29), 4.39 (1H, m, H-3), 5.38 (1H, broad s, H-6), and 4.30 (1H, d, J=7.7 Hz, H-1º).
White powder, m.p. 260–263°C, Rf 0.57 (TLC, S2); EIMS, M+ at m/z 618 compatible with C36H58O8, m/z 456 ascribe to the mass of triterpene (aglycone), corresponding to C30H47O3, m/z 438 (aglycone-H2O), 426 (aglycone-2Me), 410 (aglycone-COOH+Me), 248 and 189, 133, the ion at m/z 161 stands for a hexose sugar.
Yellow powder, UV λmax nm: (MeOH) 256, 267.1, 292sh, 357; MeOH+NaOMe, 272, 291, 325sh, 415; MeOH+NaOAc, 273, 315, 390; MeOH+AlCl3, 274, 292, 340sh, 425 MeOH+AlCl3+HCl; 272, 303sh, 360sh, 403. 1H-NMR (500 MHz, DMSO) δH 7.82 (2H, d, J=8.2 Hz, H-2º, 6º), 6.84 (2H, d, J=8.2 Hz, H-3º,5º), 6.28 (1H, d, J=1.9 Hz, H-6), 5.30 (1H, d, J=7.6 Hz, H-1ºº of glucose), 3.27–3.57 (m, rest of glucose protons). Acid hydrolysis gave kaempferol and glucose.
Yellow powder, m.p. 224–226oC; brown fluorescence in UV, Rf 0.34, UV λmax nm: (MeOH) 254, 265sh, 353; (NaOMe) 270, 331sh, 415; (NaOAc) 271, 311sh, 394; (AlCl3) 264, 296, 366sh, 400; (AlCl3+HCl) 262, 300, 366, 400. Acid hydrolysis gave isorhamnetin and glucose.
| Results and discussions|| |
The aqueous ethanolic extract was successively partitioned in H2O/CHCl3, H2O/EtOAc, and H2O/n-BuOH. The three fractions were then subjected to a sequence of column chromatography procedures to yield compounds I–V, VI–VIII, and IX–XII, respectively.
9, 12, 13-Trihydroxydocosan–10, 15, 19-trienoic acid (I) was isolated as a white solid with the molecular formula C22H42O5, calculated from the [M+] peak at m/z 386. Its IR spectrum showed OH and CO absorptions at 3437 and 1740 cm−1, respectively. 13C-NMR was characteristic of an unsaturated long chain fatty acid with a methyl group at δC 14.3, several methylene carbons from 23.2 to 39.91, two sp2carbons at 139.3 and 157.4, and a substituted carboxyl carbon at δC 166.98, in addition to three low-field oxygenated carbons at δC 72.99 and 77.0, bearing methane protons at δH 4.2, 3.89, and 3.58, respectively, which confirmed the presence of three hydroxyl groups; an olefinic proton signal appeared at δ 5.27. Analysis of the spectra provided evidence for the fragment and established the structure of compound I 22.
Trans-N-feruloyl tyramine-4ººº-O-β-D-glucopyranoside (II) showed EIMS, M+ at m/z 476 calculated for the molecular formula C24H30NO9. Its IR spectrum exhibited characteristic absorption bands for a hydroxyl group (3416 cm−1), conjugated carbonyl group (1646 cm−1), and conjugated double bond (1515 cm−1). Acid hydrolysis of II afforded D-glucose as determined by comparing the Rf of the hydrolysis product with that of an authentic sample using the paper chromatographic technique. The 1H-NMR spectrum [Table 1] indicated the presence of one 1,4-disubstituted aromatic ring at δH 7.19 (2H, d, J=8.4 Hz, H-2ººº, 6ººº) and δH 7.19 (2H, d, J=8.5 Hz, H-3ººº, 5ººº); one 1, 3, 4-trisubstituted aromatic ring at δH 6.95 (1H, dd, J=8.2, 1.7 Hz, H-6º) and δH 6.75 (1H, d, J=8.2 Hz, H-5º); one trans olefin at δH 6.68 (1H, d, J=15.2 Hz, H-3) and δH 4.22 (1H, d, J=12.1 Hz, H-2); and one methoxy proton at δH 3.99 (3H). From the coupling constant of the anomeric proton at δH 4.24 (1H, d, J=7.4 Hz, Glc-1), C-1 of the D-glucopyranose was determined to be in the β-configuration. Analysis of the 13C-NMR [Table 1]; δC-1" 175, δC-1 40.5) and the molecular formula of II revealed that C-1ºº and C-1were linked by a nitrogen atom. The current analysis and comparison with the data in the literature suggested the structure of compound II 23.
The two coumarins III and IV were isolated from the CHCl3 extract. Umbelliferone (III) showed shine blue fluorescence under UV light (366) and when sprayed with I2/KI reagent turned into a colorless spot. From the results of 1H-NMR analysis and by cochromatography with the reference substance, compound III was identified.
Scopoletin (IV) showed strong blue fluorescence under UV light (366) and when sprayed with I2/KI reagent turned into brown spot. The UV spectrum of IV in MeOH showed absorption bands at 229, 250sh, 260sh, 295sh, and 342 nm, which suggested a 6,7-dioxgenated coumarin skeleton. From the results of 1H-NMR analysis and by cochromatography with the reference substance, compound IV was identified 24.
Three known sterols (V) isolated from the CHCl3 extract gave positive results for the Liebermann test for sterols and showed an [M+] peak at m/z 412 (25.0%), 414 (17%), and 416 (1.40%) corresponding to C29H48O, C29H50O, and C29H52O, respectively. Because of its occurrence with the identified sterols 25, the sterol with M+ at m/z 414 (17.0%) was identified as β-sitosterol, the sterol with M+ at m/z 412 (25.0%) was identified as stigmasterol, and the sterol with M+ at m/z 416 was identified as sitostanol.
Three compounds VI, VII, and VIII were isolated from the EtOAc extract.
Olean-12-en-3,28 diol (VI) gave a positive Liebermann test for triterpenes. The compound with M+ at m/z 441 (8.02%) was identified as C30H50O2, with a peak at 411 (45.0%). Spectral analysis suggested the structure of the compound 21.
Olean-12-en-28-oic acid (VII): the IR spectrum showed strong bands near 3415 (OH) and 1735 cm−1 (CO): two bands, 1390–1375 and 1369–1354 cm−1, in the so called ‘A-region’ and three bands at 1328–1318, 1303–1296, and 1267–1248 cm−1 in the ‘β-region’; its mass gave an M++1 peak at m/z 457 (2.02%), corresponding to C30H48O3, fragmentation characteristic with respect to oleanane triterpenoids having D12 : 13 unsaturation. The ion at m/z 189 represents rings A and B in the dehydrated form. Previous spectral data and chemical analysis elucidate the structure of this compound 21.
3-Methyl kaempferol (VIII) was identified from the analysis of its UV spectra in MeOH before and after the addition of different shift reagents and from the analysis of its 1H-NMR spectral data 20; this was further confirmed by cochromatography with a reference substance.
Stigmasterol-3-β-O-D-glucopyranoside (IX) showed an EIMS M+ peak at m/z 576 (9.45%), corresponding to the molecular formula C35H60O6, m/z 163 (13.54) of one hexose sugar. IR spectroscopy revealed bands Vmax cm−1, 3421 OH, 1730–1446 (C=C), 1129, 1076, 1055, and 1015 (ether linkage of glycoside). 1H-NMR revealed one anomeric proton at 4.43 (d, J=6.78), indicating the sugar to be in the β-configuration. Thus, from the large JH1,H2 coupling constant, the structure of this compound was elucidated as stigmasterol-3-β-O-D-glucopyranoside 25.
3-O-[β-D-glucopyranosyl]oleanolic acid (X) showed an M+ peak at m/z 618, corresponding to the molecular formula C36H58O8, and a fragment ion at m/z 456, corresponding to H30H48O3. This is ascribed to the mass of triterpene acid having a &Dgr;12 aglycone. IR revealed bands Vmax cm−1, 3421 OH, 1730–1446 (C=C), 1129, 1076, 1055, and 1015 (ether linkage of glycoside).
Kaempferol 3-O-β-glucopyranoside (XI) and isorhamnetin 3-O-β-glucopyranoside (XII) gave typical brown fluorescence under UV for the C-3-substituted flavonoid glycosides. Acid hydrolysis yielded glucose and kaempferol or isorhamnetin, respectively. The structures of compounds XI and XII were confirmed by 1H-NMR and cochromatography with authentic reference samples 26. Isolation of these compounds from S. inermis has not been reported previously.
| Conclusion|| |
Twelve compounds were isolated and identified for the first time from the 70% ethanolic extract of S. inermis. Some of these compounds contain different hydroxyl groups and the others were terpenoids, which help scavenge free radicals and inhibit COX and various mediators involved in the pathogenesis of pain relief. The chloroform fraction showed more potent inhibitory activity than the ethanol extract, whereas the 70% ethanolic extract was more potent than the chloroform fraction in antinociceptive activity.
| References|| |
|1.||El Hadidi MN, Fayed AA. Materials for excursion flora of Egypt. Taeckholmia. 1994–95;15:57 |
|2.||Boulos L Flora of Egypt, checklist. 1995;1 Cairo, Egypt Al Hadara Publisher:118 |
|3.||Karawya MS, Wassel GM, Baghdadi HH, Ahmed ZF. Isolation of methyl carbamate from four Egyptian Salsola species. Phytochemistry. 1972;11:441–442 |
|4.||Wassell GM, Baghdadi HH, El Difrawy SM. Phyto-ecdysone from some wild Egyptian Salsola species. Fitoterapia. 1979;50:51–52 |
|5.||Woldu Y, Abegaz B. Isoflavonoids from Salsola somalensis. Phytochemistry. 1990;29:2013–2015 |
|6.||Tundis R, Menichini F, Conforti F, Loizzo MR, Bonesi M, Statti G, Menichini F. A potential role of alkaloid extracts from Salsola species (Chenopodiaceae) in the treatment of Alzheimer’s disease. J Enzyme Inhib Med Chem. 2009;24:818–824 |
|7.||Beyaoui A. New antioxidant bibenzyl derivative and isoflavonoid from the Tunisian Salsola tetrandra Folsk. Nat Prod Res. 2012;26:235–242 |
|8.||Tundis R. Inhibitory effects on the digestive enzyme alpha-amylase of three Salsola species (Chenopodiaceae) in vitro. Pharmazie. 2007;62:473–475 |
|9.||Oueslati MH, Jannet HB, Mighri Z, Chriaa J, Abreu PM. Phytochemical constituents from Salsola tetrandra. J Nat Prod. 2006;69:1366–1369 |
|10.||Swart P. Biological activities of the shrub Salsola tuberculatiformis Botsch.: contraceptive or stress alleviator? Bioessays. 2003;25:612–619 |
|11.||Abegaz BM, Woldu Y. Isoflavonoids from the roots of Salsola somalensis. Phytochemistry. 1991;30:1281–1284 |
|12.||Saratikov AS, Vengerovskiľ AI. New hepatoprotective agents of natural origin. Eksp Klin Farmakol. 1995;58:8–11 |
|13.||Beyaoui A, Chaari A, Ghouila H, Ali Hamza M, Ben Jannet H. New antioxidant bibenzyl derivative and isoflavonoid from the Tunisian Salsola tetrandra Folsk. Nat Prod Res. 2012;26:235–242 |
|14.||Nofal SM. Evaluation of some biological activities of the alcoholic extracts of Salsola volkensii and Salsola villosa in rats. Egypt J Pharm Sci. 2004;45:41–52 |
|15.||Assarehzadegan MA. Allergy to Salsola Kali in a Salsola incanescens-rich area: role of extensive cross allergenicity. Allergol Int. 2009;58:261–266 |
|16.||Flora SJS. Role of free radicals and antioxidants in health and disease. Cell Mol Biol. 2007;53:1–2 |
|17.||Si H, Liu D. Isoflavone genistein protects human vascular endothelial cells against tumor necrosis factor-a-induced apoptosis through the p38β mitogen-activated protein kinase. Apoptosis. 2009;14:66–76 |
|18.||Blonska M, Czuba ZP, Krol W. Effect of flavone derivatives on interleukin-1β (IL-1β) mRNA expression and IL-1β protein synthesis in stimulated RAW 264.7 macrophages. Scand J Immunol. 2003;57:162–166 |
|19.||Ahlam HM, Fatma SE. Antioxidant, anti-inflammatory and analgesic effects of Salsola inermis. J Arab Soc Med Res. 2007;2:45–52 |
|20.||Mabry TJ, Markham KR, Thomas MB The systematic identification of flavonoids. 1970 New York Springer Verlag |
|21.||Djerassi C, Budzikiewicz H, Wilson JM. Mass spectrometry in structural and stereochemical problems unsaturated pentacyclic triterpenoids. Tetrahedron Lett. 1962;3:263–270 |
|22.||Kato T, Yamaguchi Y, Abe N, Uyehara T, Namai T, Kodama M, Shiobara Y. Structure and synthesis of unsaturated trihydroxy c 18 fatty. Acids in rice plants suffering from rice blast disease. Tetrahedron Lett. 1985;26:2357–2360 |
|23.||Yahagi T, Yamashita Y, Daikonnya A, Wu J-B, Kitanaka S. New feruloyl tyramine glycosides from Stephania hispidula Yamamoto. Chem Pharm Bull (Tokyo). 2010;58:415–417 |
|24.||Murray ROH, Mendez J, Brown SA The natural coumarins. 1982 Chichester, New York, Brisbane, Toranto and Singapore John Wiley & Sons Ltd |
|25.||Elgamal MHA, Abdel Hady FK, Soliman HSM. Constituents of local plants. Phytochemical screening of some selected local saponin bearing plants. Bull Natl Res Centre (Cairo). 1990;15:215–220 |
|26.||Kojima H, Sato N, Hatano A, Ogura H. Sterol glucosides from Prunella vulgaris. Phytochemistry. 1990;29:2351–2355 |