Structures of three new 24,24‐dimethyl‐Δ⁷‐sterols fromGynostemma pentaphyllumfromGynostemma pentaphyllum

Abstract

The structures of three new sterols isolated from Gynostemma pentaphyllum (Cucurbitaceae) have been shown by chemical and spectroscopic methods to be 24, 24dimethyl-5a-cholest-7-en-3fl-ol, (22E)-24,24-dimethyl-5acholesta-7,22-dien-3fl-ol and 24,24-dimethyl-5a-cholesta-7,25-dien-3fl-ol. Lipids 21, 515-517 (1986).Gynostemma pentaphyllum Makino (Japanese name, Amachazuru), a Cucurbitaceae plant, is known to contain many kinds of dammarane saponins (1, and references cited therein}. We have recently shown that {22E, 24R)-24ethyl-5a-cholesta-7,22-dien-3p-ol (chondrillasterol, [24R]ld), along with its (24S)-epimer (spinasterol, [24S]-1d), consists of the most predominant component of the sterol constituents of this plant (2). This paper describes our further study of the sterol constituents of the aerial parts of G. pentaphyllum, which led to the isolation and characterization of three new 24,24-dimethyl-hT-sterols. EXPERIMENTAL PROCEDURESGeneral methods and materials. Recrystallizations were performed in acetone/MeOH. Melting points imp) taken on a heat block were uncorrected. Preparative (0.5 mm thick) thin layer chromatography (TLC) on silica gel with hexane/EtOAc (6:1, v/v) and argentation TLC (silica gel/ AgNO3, 4:1, w/w) with CCL/CH~C12 (5:1, v/v) were developed three and four times, respectively. The bands on silica gel and argentation TLC were observed under UV light (3600 A) after spraying with a 0.05% solution in EtOH of rhodamine-6G and 2",T-dichlorofluorescein, respectively. Preparative high performance liquid chromatography (HPLC) was carried out on a Partisil 5 ODS-2 column (25 cm • 10 mm id) (Whatman, Clifton, New Jersey} with MeOH as a mobile phase {flow rate, 4 ml! min). Gas liquid chromatography (GLC) was performed with a Shimadzu GC-4CM instrument on a SCOT OV-17 glass capillary column (30 m • 0.3 mm id, column temperature 260 C). The Rc-values (relative mobilities) in the argentation TLC and the relative retention times (RRT) in the HPLC and GLC were expressed relative to cholesterol acetate (1.00). Mass spectra (EI-MS, 70 eV) were taken on a Hitachi M-80B double focusing gas chromatograph-mass spectrometer by means of a probe injection. Proton ('H) nuclear magnetic resonance (NMR) spectra were recorded on a Hitachi R-250 (250 MHz) or on a JEOL FX-100 (100 MHz, Japan Electron Optics Lab. Co., Tokyo} spectrometer in a CDCl~ solution, with tetramethylsilane as the internal standard. Hydrogenation was achieved in EtOH over PtO~ at atmospheric pressure and temperature overnight. An authentic specimen of 24,24-dimethyl-5a-lanosta-9(ll),25-dien-3fl-ol (2c) was supplied by W. H. Hui (University of Hong Kong) and its *To whom correspondence should be addressed.25-dihydro derivative, 24,24-dimethyl-5a-lanost-9(11)-en-3g-ol (2a), was prepared from 2c by partial hydrogenation.Sterol isolation from G. pentaphyllum. The sterol fraction (125 mg) obtained from MeOH extract (80 g) of the air-dried aerial parts (leaves and stems) of G. pentaphyllum (520 g) (2) was acetylated in Ac~O/pyridine at room temperature o...

Chemistry and Pharmacology of Gynostemma pentaphyllum

“…Chondrillasterol and its (24S)-epimer, spinasterol, are the most predominant sterol component. The usual configurations at C-24 are 24-alkyl-D 5 -,D 7 -,D 8 -sterols and 24,24-dimethyl-D 7 -sterols (Akihisa et al, 1986). The structures of the 24,24-dimethyl-D 7 -sterols is unusual as they contain acyclic, quaternary carbon groups in the side chain (C-24) which is common in marine sponges (Akihisa et al, 1986).…”

“…The usual configurations at C-24 are 24-alkyl-D 5 -,D 7 -,D 8 -sterols and 24,24-dimethyl-D 7 -sterols (Akihisa et al, 1986). The structures of the 24,24-dimethyl-D 7 -sterols is unusual as they contain acyclic, quaternary carbon groups in the side chain (C-24) which is common in marine sponges (Akihisa et al, 1986). 4a-methylsterols (Akihisa et al, 1990), 14a-methylsterols (Akihisa et al, 1987), 24,24-dimethylsterols (Akihisa et al, 1988), (24R=a)-and (24S=b) epimers of 14a, 24-dimethyl-5a-cholest-9(11)-en-3b-ol also occur (Akihisa et al, 1989a).…”

Anti-cancer effects of Gynostemma pentaphyllum (Thunb.) Makino (Jiaogulan)

“…Sterols are composed of 17 carbon atoms across four rings, i.e., three 6-carbon rings and a single 5-carbon ring, with a side chain extending from C17 containing nine or ten carbon atoms (Additional file 1 : Table S1). Eighteen sterols were isolated from GpM and fully characterized using a unique method from 1986 to 1990 [ 61 – 67 ]. Briefly, GpM was extracted with CH 2 Cl 2 , and the extracted lipids were saponified with 5 % KOH in MeOH.…”