Plants and microorganisms, being the major source of many drugs, have attracted scientists from ancient times. However, until recently an insignificant part of the plants and some microorganisms have scientifically been evaluated for their medicinal values. The present study was undertaken to discover new drug candidates from natural sources. Extensive chemical studies with 60 medicinal plants and several microbial strains of Bangladesh have resulted in the isolation and characterization of 150 compounds, including 50 new molecules. Terpenoids and alkaloids were the major constituents among the isolated compounds. The crude extractives and several purified molecules demonstrated statistically significant inhibition of growth of microorganisms, antioxidant, antidiabetic and HIV-inhibitory activities. Usnic acid, a lead compound isolated from the lichen, Parmelia kamtschandalis, showed potent antimicrobial activity, whereas dehydroaltenusin obtained from a Streptomyces sp. exhibited significant HIV-inhibitory effects.
Five compounds namely, sterekunthal B (1), sterequinone C (2), p-hydroxybenzaldehyde (3), p-hydroxyphenylmethyl ketone (4) and stigmasterol (5) were isolated from methanolic extract of the stem bark of Stereospermum chelonoides. The structures of compounds 1-5 were established by extensive spectroscopic studies, notably high field NMR and MS. This is the first report of occurrence of 1-5 from Stereospermum chelonoides.
Key words: Stereospermum chelonoides, Bignoniaceae, Sterekunthal B, Sterequinone C
Dhaka Univ. J. Pharm. Sci. Vol.4(1) 2005
The full text is of this article is available at the Dhaka Univ. J. Pharm. Sci. website
The genus Momordica (Cucurbitaceae) has recently attracted attention because of reports that extracts exhibit antidiabetic activity (1). Previous investigations of M. cochinchinensis Spreng. have yielded oleanolic acid (2), its 1-oxo derivative momordic acid (3) and a steroidat compound named bessisterol (4). Many Cucurbitaceae are intensely bitter due to the presence of cucurbitacins (5) and these have recently been reported from Momordica (6). In this paper we report the presence of another type of bitter principle, the diterpene columbin (1), a compound normally associated with the Menispermaceae but which has previously been recorded in another cucurbitaceous genus, Melothris (7). The structure of 1 was established in the 1960's, primarily on the basis of chemical modifications (8) and through X-ray analysis of its C-8 epimer isocolumbin (9). Surprisingly 1H-NMR data on columbin is far from complete and the 13C-spectrum does not appear to have been published. Here we give the results and interpretation of a high-field NMR investigation of 1 isolated from a new source, the roots of M. cochinchinensis. 1613 l2J 1 The 1H-NMR spectrum of 1 defined all 22 protons (Table 1). Singlets were observed for two methyl substituents,
Lupeol (1) and Stigmasterol (2) were isolated from the crude extracts of the stem bark of Citrus macroptera (Family: Rutaceae) for the first time. The n-hexane, dichloromethane and methanol extracts were screened in vitro for antioxidant activity using the 1, 1-diphenyl-2-picrylhydrazyl-hydrate (DPPH) free radical scavenging assay. The hot methanol extract showed potential antioxidant activity (IC50: 178.96 μg/ml) whereas the cold methanol and dichloromethane extracts showed moderate activity (IC50: 242.78 μg/ml and 255.78 μg/ml respectively). Mild antioxidant activity was observed with the n-hexane extract of the stem bark of Citrus macroptera (IC50: 422.94 μg/ml). Key words: Citrus macroptera, Rutaceae, Lupeol, Stigmasterol, Antioxidant.  doi: 10.3329/bjsir.v43i4.2235 Bangladesh J. Sci. Ind. Res. 43(4), 449-454, 2008
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