TLC separation and antioxidant activity of flavonoids from Carissa bispinosa, Ficus sycomorus, and Grewia bicolar fruits

Background: Carissa bispinosa, Ficus sycomorus, and Grewia bicolar are edible fruit plants that grow in the wild. The plants produce yellow-, red-, and purple-colored fruits and thus can be good sources of flavonoids for fighting oxidative reactions in humans, food, and the pharmaceutical industry. The present study aimed at isolating flavonoids from C. bispinosa, F. sycomorus, and G. bicolar fruits and determining their antioxidant activity using the 2, 2-diphenyl-1picrylhydrazyl (DPPH) and 2, 2-azino-bis 3-ethylbenz-thiaz-oline-6-sulfonic acid (ABTS) model radical assays. Methods: Analytical and preparative thin-layer chromatography was used to isolate flavonoids from the fruits using methanol/chloroform/hexane (7:2:1, v/v/v) as a mobile phase system. The ABTS and DPPH radical scavenging methods were used to test for the antioxidant activity of the samples, using quercetin and catechin as reference standards. Results: Thin-layer chromatographic profiling revealed two different types of flavonoids from each plant. C. bispinosa yielded two flavonoid bands, Rf values 0.11 and 0.38; G. bicolar yielded two flavonoid bands, Rf values 0.63 and 0.81; and F. sycomorus also yielded two types of flavonoids, Rf values 0.094 and 0.81. All the extracted flavonoids exhibited significant antioxidant activity of over 80% at a concentration of 200 mg/L. The order of radical scavenging activity for the 200-mg/L samples is G. bicolar Rf (0.81) > C. bispinosa Rf (0.113) > F. sycomorus Rf (0.094) > F. sycomorus Rf (0.047) > C. bispinosa Rf (0.38) > G. bicolar Rf (0.63). G. bicolar (Rf = 0.81) exhibited antioxidant activity that was superior to that of catechin. Conclusion: The present study results show that C. bispinosa, F. sycomorus, and G. bicolar contain different flavonoid types with significant antioxidant activity of over 80% at a concentration of 200 mg/L. Therefore, the fruits can be used as a source of natural antioxidants which can be used as nutraceuticals to promote health, as preservatives to delay peroxidation of foods, and as flavoring for packed foods.