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.

Characterization of transport of chlorhexidine-loaded nanocapsules through hairless and wistar rat skin.

Nanocapsules appear a promising approach as a drug system for topical application. However, the transport mechanism of nanocapsule-associated drug through the skin is still being questioned. In the present study, the transport of chlorhexidine-loaded poly(epsilon-caprolactone) nanocapsules through full-thickness and stripped hairless rat skin was investigated in static-diffusion cell. The chlorhexidine permeation profiles fitting the Fickian diffusion model showed that the drug encapsulation reduced the percutaneous drug absorption through stripped skin. Possible nanocapsule transport within skin conducts was suggested from the analysis of permeation parameters and confirmed by confocal laser microscopy studies. Furthermore, the chlorhexidine permeation and drug release data were highly correlated, suggesting that the magnitude of percutaneous absorption was controlled by the diffusion across the polymeric carrier. The behavior of nanocapsules at the skin interface was investigated by contact angle and surface tension measurements. The small 'wetting' of the nanocapsule on the stratum corneum surface preserved the mechanical integrity of the carrier characterized by a high specific surface at the skin interface. The flexibility of the nanocapsules assured a satisfying bioadhesion to the skin, whereas the rigidity of the carrier limited the molecular 'spill' into the skin and controlled the drug delivery to the skin.