Phytochemical and antimicrobial investigation of Bersama abyssinica (Melianthaceae)

Infectious diseases are disorders caused by organisms (bacteria, viruses, fungi or parasites) with different clinical manifestations. During the last decades, great interest has been devoted to the study of microbes in order to provide solutions to problems they pose. The importance given to the study of microbial diseases follows the emergence of new diseases that weaken the immune system, as well as the appearance of new microbial strains that are increasingly resistant to the most commonly used drugs. Medicinal plants are considered as a promising alternative for the discovery of new effective drugs. Plants of genus Bersama belongs to the Melianthaceae family are traditionally used by some communities in Cameroon for medicinal purposes to treat many diseases such as stomach infections, diarrhea, cholera. Previous phytochemical investigation on this species led to the isolation of triterpenes, flavonoids, anthraquinones and xanthone which displayed antibacterial, antifungal, and antioxidant activities. In our continuous search for bioactive extracts fractions and compounds from Cameroonians medicinal plants, we undertook in this case of this work the chemical and antimicrobial investigation of Bersama abyssinica. In this study, the ethanolic extract of Bersama abyssinica stem bark was prepared and successively extracted with n-Hexane, ethyl acetate and n-BuOH to yield 50 g, 56 g and 60 g fractions respectively. The antibacterial screening carried out on extract and fractions showed that n-Hexane was not active while crude extract, ethyl acetate and n-BuOH fractions displayed good activities against E. coli and S. aureus with IC50 values ranging from 31.2 to 62.5 μg/ml. Chemical investigation of n-hexane and ethyl acetate fractions led to the isolation of 9 known compounds: mangiferin, oleanolic acid, ursolic acid, betulinic acid, betuline, lupenone, lupeol, β-sitosterol 3-O-β-D-glucopyranoside, β-sitosterol.
Key words: Bersama abyssinica, Melianthaceae, infectious diseases, antibacterial, E. coli, S. aureus