ANTIMICROBIAL CONSTITUENTS FROM THE LEAF LATEX OF ALOE PULCHERRIMA GILBERT & SEBSEBE

The loss of effectiveness of chemotherapy constitutes the greatest threat to the control of microbial diseases due to rapidly evolving crisis of antibiotic resistance and this has contributed to the rise of patient morbidity. In Ethiopian traditional medicine, the endemic plant Aloe pulcherrima Gilbert & Sebsebe is used for the treatment of various infectious diseases. In our continuing search for antimicrobial agents from plants, we have investigated the leaf latex of this plant. The results revealed that the latex possesses varying degrees of antimicrobial activity when tested against 21 bacterial and 4 fungal strains using the disk diffusion method. Further analysis of the latex using preparative thin layer chromatography (PTLC) resulted in the isolation of two major compounds identified as 7-hydroxyaloin (1) and nataloin (2) on the basis of spectroscopic methods including HR-ESIMS, 1H and 13C-NMR spectral data. The latex and isolated compounds showed comparable activity with that of ciprofloxacin against most of the tested bacteria but highest effect was observed against the different Vibrio cholerae strains tested (MIC: 10 μg/ml). In general, the activity of the test substances on the fungal pathogens tested was relatively weaker with the exception of nataloin which showed comparable activity (MIC: 400 μg/ml) with that of the griseofulvin against Candida albicans and Penicillium spp. The present findings support the traditional use of the plant for the treatment of infectious diseases.