Antimicrobial and cytotoxic activities of indole alkaloids and other constituents from the stem barks of Rauvolfia caffra Sond (Apocynaceae)

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.

GRAPHICAL ABSTRACT

Keywords:

• Rauvolfia caffra
• Apocynaceae
• rauvolfianoids
• antimicrobial activity
• cytotoxicity

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Funding

We gratefully acknowledge the TWAS scholarship for financial support and travel grants (CIIT-TWAS sandwich PG-fellowship-grant N° 3240299466) for Mr. Bitombo André to Pakistan. The authors are also grateful to the Department of Chemie, Universität of Fribourg for scholarships for foreign researchers (grant N° 319430) and the Bochet’s Group for technical assistance to Mr Bitombo. We also thank Mr. Victor Nana (National Herbarium of Cameroon) for his assistance in the collection and identification of the plant material. We also grateful to the UMR 152 PHARMA-DEV, Université de Toulouse, IRD, UPS, France, for LC-MS analysis.