Phytochemical screening, Antimycobacterial activity of three medicinal Cameroonians plants and Acute toxicity of hydroethanolic extract of Vitellaria paradoxa

Abstract

Tuberculosis (TB) is an infectious disease caused by the Mycobacterium tuberculosis (M. tuberculosis) complex, resposible  for health problems in developing countries. In Africa, various medicinal plants are traditionally used to treat  TB.  The aim of this study is to carry out the phytochemical screening, to evaluate the antimycobacterial activity of the crude extracts of three medicinal plants present in Cameroon (Zingiber officinale, Vitellaria paradoxa and Alstonia boonei) and the acute toxicity of hydroethanolic extract of Vitellaria paradoxa. The phytochemical screening was obtained by hydroethanolic extraction  and decoction. Inhibitory parameters of antimycobacterial activities were determined using the microplate alamar blue assay against M. tuberculosis H37Rv (ATCC 27294) and on one M. tuberculosis clinical strain. The crude extract with the best antimycobacterial activity was used for the acute toxicity assessment according to the OECD protocol. The results of the phytochemical screening revealed the presence of triterpenes and steroids in all the extracts, whereas  phenols were only present in the decoction of Alstonia boonei. All extracts tested showed antimycobacterial activities. The hydroethanolic extract of V. paradoxa  presented the best antimycobacterial activity with MICs of 78.13 and 625 μg/mL and MBCs of 78.13 and 2500 μg/mL respectively on M. tuberculosis H37Rv and on M. tuberculosis clinical strain. The results of the acute toxicity evaluation of V. paradoxa  showed a lethal dose 50  greater than 5000 mg/kg compared to control. The antimycobacterial activity of all the plant extracts used in this study justifies the traditional use of these medicinal plants on the treatment of  TB. Keywords: Zingiber officinale, Vitellaria paradoxa, Alstonia boonei, Phytochemical screening, Antimycobacterial activity, Acute toxicity.