Phytochemical characterization and in vitro antibacterial activity of Xeroderris stuhlmannii (Taub.) Mendonca & E.P. Sousa bark extracts

The use of herbal medicine is common in many rural communities in Zimbabwe because generic drugs are expensive and not readily available. In this work, we documented the important phytochemicals from Xeroderris stuhlmannii (Taub.) Mendonca & E.P. Sousa (Murumanyama in Shona), bark extracts and tested their antibacterial activity in order to demonstrate its potential as an antimicrobial agent. Qualitative screening of secondary metabolites confirmed the presence of alkaloids, flavonoids, terpenoids, steroids and polyphenols in the crude bark extracts. The MICs values for the crude extracts on six bacterial strains ranged from 0.23-0.80 mg/mL. Antimicrobial tests showed higher potency for crude bark extracts on E. Coli (MIC, 0.232 mg/mL) and lower potency on coliform (MIC, 0.798 mg/mL). LC-MS/MS analysis of various fractions confirmed the presence of twenty-eight phytochemicals whereas, twelve phytochemicals were identified using GC-MS. Both techniques confirmed the presence of ursolic acid, roburic acid, reticuline, rotenone and p-coumaric acid glucoside in hexane and methanol extracts. In summary, our findings show that Xeroderris stuhlmannii (Taub.) Mendonca & E.P. Sousa contain many phytochemical compounds that have antimicrobial activity. Moreover, some of the compounds in the bark extract have been shown to possess antioxidant, antiviral, antitumor and anti-inflammatory properties. Thus, Xeroderris stuhlmannii (Taub.) Mendonca & E.P. Sousa barks can act as a useful herbal supplement for treatment of a number of diseases in rural communities where modern drugs are expensive and not readily available.