Phytochemical and Antibacterial activity of the Pods and Leaves extracts of Moringa stenopetala and Docking studies of stigmasterol.

Abstract

Moringa stenopetala is an endemic vegetable tree in east Africa and used in southern Ethiopia as food and medicine. Through the plant has significant contribution as medicine, there is no prior chemical and pharmacological reports on the pods of this species. Therefore the main objective of this research is to conduct phytochemical, antibacterial and docking studies of the pods of Moringa stenopetala. In view of this the pods and leaves were successively extracted with n-hexane, EtOAc and MeOH. The phytochemical screening of the n-hexane, EtOAc and MeOH extracts of pods of Moringa stenopetala shows the presence flavonoids, alkaloids and saponins. The EtOAc extract of the pods after silica gel column chromatography furnished three compounds identified as oleic acid, n-octacosane and stigmasterol while rutin was isolated from the leaves of Moringa stenopetala. The isolated compounds were characterized with IR and NMR. The extracts and isolated compounds were also evaluated for their antibacterial activities using gram negative and gram positive bacteria. The n-hexane extract of the pods showed inhibition zone of 18 mm and 13 mm against S. pneumonia and K. pseudomonas at the 2 µg/mL, respectively. This is significant compared with the positive control. On the other hand the ethyl acetate extract displayed zone of inhibition by 13 mm and 10 mm against S. aureus and S. pneumonia at 10 µg/mL, respectively. Methanol extract of the pods showed inhibition zone of 9, 10, 11, 13 and 14 mm against Shigella boydii, S. pneumonia, E. coli, S. aureus and K. Pseudomonas at 4µg/mL respectively. Docking study was performed using stigmasterol which was active against S. aureus bacteria and the ligand has 60% binding affinity with the protein. Therefore, the antibacterial activity displayed by the pods extracts of M. stenopetala corroborates the traditional use of this plant against bacteria.