Phytochemical screening and in vitro evaluation of antioxidant and antimicrobial activities of Kedrostis africana (L.) Cogn

Objective: To investigate phytochemical, antioxidant and antimicrobial activities of Kedrostis africana (K. africana). Methods: Dried tubers of K. africana were extracted in acetone, water and ethanol. The total phenol, flavonoid, proanthocyanidin and tannin contents were determined spectrometrically. The antioxidant activity was examined using 2,2-diphenyl-1-picrylhydrazyl, 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt, nitric oxide and hydrogen peroxide assays. The antimicrobial activity was determined by agar dilution method using minimum inhibitory concentration against 3 g positive and three gram negative strains while four fungal strains were also investigated. Results: Total phenol, flavonoids, proanthocyanidin and tannin contents ranged from (5.32 ± 0.01) to (10.51 ± 0.01) mg GAE/g; (42.58 ± 0.02) to (529.23 ± 0.01) mg QE/g; (15.05 ± 0.00) to (585.64 ± 0.00) mg CE/g and (0.301 ± 0.010) to (0.937 ± 0.000) mg TAE/g, respectively. The IC50 values of the ethanol extract for 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) and hydrogen peroxide were 0.054 and 0.057 mg/mL, respectively, aqueous extract had an IC50 value of 0.135 7 mg/mL for nitric oxide while the acetone extract had an IC50 value of 0.300 mg/mL for 2,2-diphenyl-1-picrylhydrazyl. The ethanol extract demonstrated effective antimicrobial activity against the tested pathogenic species with minimum inhibitory concentrations values ranging from 2.5–5.0 mg/mL for bacteria and (0.312 5–5.000 0) mg/mL for fungi, respectively. Conclusions: The tuber of K. africana showed potent free radical scavenging property and antimicrobial activity.