Isolation and in vitro antibacterial activity of astilbin, the bioactive flavanone from the leaves of Harungana madagascariensis Lam. ex Poir. (Hypericaceae).

Harungana madagascariensis is well known for its topical antibacterial properties used in the elaboration of a lot of skin hygiene products. The aim of this study was, on the one hand, to evaluate the in vitro antibacterial activities of aqueous, ethanolic and ethyl acetate crude extracts of Harungana madagascariensis leaves against bacterial strains representative of skin microflora and, on the other hand, to determine the chemical structure of the active compound. Only the ethyl acetate leaf extract presented important antibacterial activity. Its fractionation was carried out by column chromatography using silica gel 60 and it yielded 11 fractions. A bioautographic method, revealed in these fractions the presence of a flavanone as the active compound astilbin or 3-O-alpha-L-rhamnoside-5,7,3',4'-tetrahydroxydihydroflavonol which was identified on the basis of its spectroscopic data. Concerning the antibacterial activity against the representative skin microflora of the armpit and feet, MIC and MBC ranged from 25 to 250 and 100 to 750 microg ml-1, respectively. The results showed that some bacteria considered to be responsible for bad odours at the armpit and feet levels, were destroyed at 200 microg ml-1 (MBC), a concentration sparing most of the useful saprophytic microflora. The minimal inhibitory quantity (MIQs) of astilbin ranged from 50 to 100 microg.

A bioassay using the human hepatoblastoma cell line HepG2 for detecting phototoxicity of furocoumarins.

We successfully evaluated the human hepatoblastoma cell line HepG2 as a model to assess phototoxicity of coumarins. Five natural furocoumarins were tested and their phototoxic activities, obtained by measuring cell viability in the presence of UV using the MTT test, were as follows: xanthotoxin (8-MOP) >> heraclenol = trichoclin = imperatorin >> peucedanin, both in growing and confluent cell cultures. This easy-to-perform, miniaturised, quantitative and sensitive method could therefore be used as a primary screening test for phototoxicity of a large number of compounds and plant extracts.

Efficient synthesis of octandrenolone and related dipyranoacetophenones.

Octandrenolone (1) was prepared in high yield by condensation of 2', 4',6'-trihydroxyacetophenone with 3-chloro-3-methylbut-1-yne in the presence of a catalytic amount of copper(I) iodide. Methylation of 1 afforded O-methyloctandrenolone (2). Oxidation of 2 with m-chloroperoxybenzoic acid followed by hydrolysis gave the racemic trans-(+)-1-(9,10-dihydro-9,10-dihydroxy-5-methoxy-2,2,8, 8-tetramethyl-2H,8H-benzo[1,2-b:3,4-b']dipyran-6-yl)ethanone (3), which confirmed the structure of the natural product previously isolated from Melicope erromangensis.

Polyoxygenated flavones from the leaves of comptonella microcarpa

The leaves of Comptonella microcarpa have yielded one alkaloid, dictamnine, and four known polyoxygenated flavonoids, meliternatin, 3,5,8-trimethoxy-6,7-3',4'-dimethylenedioxyflavone, 7-(3-methylbut-2-enyloxy)-3,5,8-trimethoxy-3', 4'-methylenedioxyflavone (3), 7-hydroxy-3,5,8-trimethoxy-3', 4'methylenedioxyflavone. In addition, two new flavonoids were found whose structures were established on the basis of their spectral data as 7-hydroxy-3,5,6,8-tetramethoxy-3',4'-methylenedioxyflavone (1) and 7-(3-methylbut-2-enyloxy)-3,5,6,8-tetramethoxy-3', 4'-methylenedioxyflavone (2).

[Rutacea from New Caledonia. Chemical composition of stem bark of Citrus macroptera Montr]. / Rutacées de Nouvelle-Calédonie. Composition chimique des écorces de Citrus macroptera Montr.

A preliminary screening showed the occurrence of alkaloids only in stem bark of Citrus macroptera Montr. In a first work on this Citrus [only one alkaloid was identified = edulinine]. We report in this paper the isolation of two other alkaloids: (+/-) Ribalinine and Isoplatydesmine and of five aromatic compounds: two derived from cinnamic acid, three identified as syringaldehyde, vanillin and methyl/vanillinate.