Stomatostemma monteiroae: A food plant with potential medicinal and therapeutic values

Abstract

Stomatostemma monteiroae is a food plant that is widely distributed in Africa including Madagascar. The aim of the study was to evaluate the potential therapeutic value of extracts of S. monteiroae in the treatment of common pathogens. Stomatostemma monteiroae dried fruit, stem, root, and tuber were ground into fine powder and extracted with 70% acetone in water. The extracts were evaluated for the presence of antioxidant compounds and inhibitory activity on the growth of four selected disease causing bacteria. The antioxidant, microdilution and bioautography techniques were done using 96-well microtitre and TLC plates respectively. The seed extracts had the highest yield among the extracts tested (17.52%) while the lowest yield was extracted from the tuber (1.15%). The DPPH methods demonstrated the presence of antioxidant compounds in all the extracts, with the stem, tuber peel and roots indicating the presence of additional antioxidant compounds with intermediate polarity. The results suggest that all the extracts tested had clear zones of inhibition on Escherichia coli on bioautography TLC plates. This was further confirmed with quantitative microdilution assay with MICs range of 40–310 μg/mL. Also, the extracts had MIC values of 10–80 μg/mL against E. coli and Pseudomonas aeruginosa. There was a consistent MIC value of 40 μg/mL against P. aeruginosa, by all the extracts tested with the exception of the root extracts (MIC = 80 μg/mL). This is the first report on the validation of the biological activity of extracts of S. monteiroae. This study demonstrated the presence of antioxidant and potent antibacterial compounds in the extracts of S. monteiroae. In addition, the results also suggest that the extracts selectively inhibited Gram negative bacteria. This observation may support the ethnobotanical use of its extracts to treat pain, stomach and skin infections. Further work is required to identify, isolate and determine the safe use of the compounds responsible for the observed bioactivity.