Medicinal properties of whole fruit extracts of Nauclea latifolia Smith.: Antimicrobial, antioxidant and hypoglycemic assessments

Abstract

The continuous search for novel compounds against microbial infections and oxidative stress-induced debilitating diseases like diabetes has intensified in recent years. This study evaluated the phytochemical constituents, time-kill antimicrobial, antioxidant, and antidiabetic potentials of whole fruit extracts of Nauclea latifolia Smith. The antibacterial potential was evaluated using micro-broth dilution method and the degree of mortality was examined at different concentrations over a period of 2 h against Staphylococcus aureus and Shigella sonnei as representative organisms. The antioxidant activity of the extracts was determined using 1, 1-diphenyl-2-picrylhydrazyl (DPPH), nitric oxide (NO), hydrogen peroxide (H2O2) and iron chelating assays. The antidiabetic potential was determined by evaluating the inhibitory effects of the extracts on the activities of α-amylase and α-glucosidase, while the modes of the enzymes inhibition were assessed using Lineweaver-Burk kinetics.The crude extract displayed minimum inhibitory concentration (MIC) ranging between 0.19 and 1.56 mg/mL. The lowest MIC value displayed by the n-hexane, ethylacetate and n-butanol fraction was 0.19, and 0.39 mg/mL by the chloroform fraction. Total mortality was recorded by n-butanol fraction at 3xMIC (0.57 mg/mL) after 15 min of contact time and ethylacetate fraction after 60 min of contact time against Stapylococcus aureus at the same concentration. Also total mortality was recorded after 60 min of contact time at 3xMIC by n-butanol fraction against Shigella sonnei. The ethyl acetate fraction has the highest total phenol (413.4 mg/g) and total flavonol (8.3 mg/g) contents which is significantly different (p < .05) from all other extracts. For the flavonoid content, the n-butanol fraction had the highest content (35.6 mg/g) followed by n-hexane, ethylacetate and chloroform fraction, respectively. N-butanol fraction showed the highest radical scavenging activities while chloroform and n-butanol fraction showed strong inhibitory potentials against α-amylase and α-glucosidase, respectively. The results obtained showed that whole fruit of Nauclea latifolia elicited noteworthy antimicrobial, antioxidant and antidiabetic activities which are attributed to the presence of its phytoconstituents and thus support its folkloric uses in the treatment of microbial infections and oxidative stress-mediated diseases like hyperglycemia.