Antimicrobial and cytotoxic activities of indole alkaloids and other constituents from the stem barks of <i>Rauvolfia caffra</i> Sond (Apocynaceae)
André Néhémie Bitombo, Auguste Abouem À Zintchem, Alex de Théodore Atchadé, Esther Del Florence Moni Ndedi, Afsar Khan, Dominique Serge Ngono Bikobo, Dieudonné Emmanuel Pegnyemb, Christian G. Bochet
Abstract
Twenty indole alkaloids, among which two undescribed ones named rauvolfianoids A (1) and B (2), were isolated from the stem barks of Rauvolfia caffra Sond along with eight other compounds from other biosynthetic pathways. The structures were elucidated by analysis of spectroscopic data, including 1 D and 2 D NMR; absolute configurations of 1 and 2 were determined by CD exciton chirality method. Compounds 1 and 2 were evaluated for antimicrobial and anticancer activities against three bacterial strains (Escherichia coli, Shigella sp and Salmonella sp) and CRC-related opportunistic pathogens. 1 showed moderate antibacterial activity against Salmonella sp with the MIC value of 25 μg/ml, while 2 exhibited weak selective activity against all tested pathogens. In addition, these alkaloids were characterized as weak apoptosis inducers in HCT116 human colon carcinoma cell line.