Anti-microbial, anti-inflammatory and anti-oxidant bioactivities of the methanolic extract of <i>Alafia zambesiaca</i> (stem-bark)

Abstract

Alafia zambesiaca is a medicinal plant used widely in Ghana for the treatment of gastric/peptic ulcers. The objective of this study was to comparatively assess the effect of the methanolic and the diethylether extracts of the plant phytochemicals on three bioactivities indicative of gastric/peptic ulcers etiology. Using standard laboratory assays involving broth dilution, carrageenan-induced foot swelling of 7-day old chicks and DPPH radical scavenging, this study compared and contrasted the antimicrobial, the antioxidant and the anti-inflammatory bioactivities of the methanolic extract with that of the diethyl ether extract of the stem-bark of Alafia zambesiaca. Phytochemical analyses proffered mechanistic explanations for the differing solvent-specific extract bioactivities by reporting the presence of tannins, flavonoids, saponins, glycosides and triterpenoids in the methanolic extract and by demonstrating that saponin is the only detectable phytochemical in the diethylether extract. The methanolic extract was comparatively the more potent anti-oxidant in vitro as demonstrated by its relatively higher anti-oxidant capacity, its comparatively higher total phenolic content and its disproportionately lower IC5_0’s in the DPPH and H₂O₂ antioxidant assays. Consistently for each of the panel of four bacterial and two fungal pathogenic microbial cell lines, the methanolic extract showed higher anti-microbial activity recording, in each case, MICs that were quantitatively lower than that of the diethylether extract. In vivo anti-inflammatory activity using the carrageenan induced chick feet edema method indicated the methanolic extract’s evocation of a dose-dependent reduction in foot edema and the diethyl ether extract’s lack of display of measurable anti-inflammatory activity. Taken together, the more polar methanolic extract contains quantitatively more phytochemicals that have qualitatively more potent bioactivities and this observation gives credence to the use of aqueous stem-bark extracts of Alafia zambesiaca for the ethnomedicinal management of gastric ulcers. Alafia zambesiaca mediates its anti-ulcer effects in gastric mucosa possibly through polar phytochemical-triggered suppressive effects on microbial proliferation, via polar phytochemical-evoked mitigation of concurrent cellular oxidative stress and through polar phytochemical-modulation of inhibitory effects on cellular inflammatory events.