RESUMO
OBJECTIVE: To evaluate the phytochemical constituents and antioxidant activities of aqueous extract of Schotia latifolia (S. latifolia) bark locally used for the treatment of oxidative stress-induced ailments in South Africa. METHODS: The antioxidant and free radical scavenging activity of aqueous extract of the plant was assessed against 1,1-diphenyl-2-picrylhydrazyl (DPPH), nitric oxide (NO), 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) and the ferric reducing agent. Total phenolics, flavonoids, flavonols and proanthocyanidins were also determined to assess their corresponding effect on the antioxidant activity of this plant. RESULTS: The activities of plant extract against DPPH, ABTS and NO radicals were concentration dependent with IC50 value of 0.06, 0.05 and 0.05 mg/mL, respectively. The reducing power of the extract was greater than that of butylated hydroxyl toluene (BHT) and ascorbic acid which were used as standard drugs in a concentration dependent manner. The total phenolics content of the aqueous bark extract was (193.33±0.03 TE/g), followed by flavonoids (72.70±0.01 QE/g), proanthocyanidins (48.76±0.00 CE/g) and flavonols (47.76±0.21 QE/g). Phytochemical analysis revealed the presence of percentage tannin (11.40±0.02), alkaloid (9.80±0.01), steroids (18.20±0.01), glycosides (29.80±0.01) and saponins (6.80±0.00). The results exhibited a positive linear correlation between these polyphenols and the free radical scavenging activities. CONCLUSIONS: Our findings provide evidence that the crude aqueous extract of S. latifolia is a potential source of natural antioxidants and this justifies its uses in folkloric medicines.
