In Vitro Antimicrobial and Antioxidant Activities of Anthrone and Chromone from the Latex of Aloe harlana Reynolds

In the search for new antimicrobial and antioxidant compounds from plants, the latex of the medicinal plant Aloe harlana Reynolds from Ethiopia was subjected to bioassay-guided fractionation, which led to the isolation of two known compounds, anthrone (aloin) and chromone (7-O-methylaloeresin A). The latex and its two constituents were assessed for their possible antimicrobial activities against 23 bacterial and four fungal strains using the disc diffusion method and their antioxidant activity by two complementary test systems, namely 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and 2-deoxyribose degradation assay methods. The isolated compounds showed promising results against various pathogenic bacterial and fungal strains in comparison with standard drugs. Moreover, 7-O-methylaloeresin A exhibited good activity against multiple drug resistant Staphylococcus aureus (NCTC 11994) and Salmonella typhimurium (ATCC 1255) with MIC values of 0.72 and 0.18 mM, respectively. Among the fungal strains tested, Candida albicans (ATCC 10231) was the most susceptible organism to the latex and the two isolated compounds. The latex and isolated compounds also showed significant activities on both antioxidant assays with the highest activity being observed for 7-O-methylaloeresin A, which gave IC(50) values of 0.026 mM and 0.021 mM for DPPH and 2-deoxyribose degradation assay, respectively. These findings support the traditional uses of the plant for the treatment of various infectious and inflammatory diseases. Copyright (C) 2011 John Wiley & Sons, Ltd.