Antimicrobial Activity of Lupeol and β-Amyrin (Triterpenoids) Isolated from the Rhizome of Dolichos pachyrhizus Harm

Dolichos pachyrhizus (Annonaceae) has been traditionally used in Africa to treat syphilis and many other microbial infections. However, no phytochemical study and antimicrobial investigations have been conducted on this species. Thus there is need for the discovery and development of new antibiotics and anifungal. The triterpenoids [Lupeol (1) and β-amyrin (2)] isolated from rhizome of Dolichos pachyrhizus (Harm) were evaluated for their antimicrobial activity against some selected Gram positive bacterial, Gram negative bacterial and Fungal isolates. The antimicrobial activity of the crude extract and compounds isolated was determined using agar well diffusion method. The compounds exhibited antimicrobial activity against most of the tested bacteria with minimum inhibitory concentration (MIC) and minimum bactericidal/fungicidal concentrations (MBC/MFC) values ranging from 2.5 to 20 mg/ml and 5 to 40 mg/ml, respectively. The triterpenoids could be a potentially effective antimicrobial agent to combat infectious diseases. The structures of the compounds were elucidated using modern spectroscopic and spectrometric techniques such as nuclear magnetic resonance (NMR) and mass spectrometry (MS) to be Lupeol and β-amyrin.