Free radical scavenging activities of phytochemical mixtures and aqueous methanolic extracts recovered from processed coffee leaves

It is well known that the choice of extraction solvents greatly affects both phytochemical composition and related bioactivity of plant extract. Herein, we show that coffee leaf extracts derived from 80% methanol have no effect on basal nitric oxide production in Raw 264.7 cells, whereas, a different result was observed with a previous hot water extract. Phytochemical mixtures formulated to contain equivalent amounts of CQAs, mangiferin and rutin know to present in coffee leaves showed a relatively low (3.5-18.5%, TPC; 17.6-31.6%, ABTS; 7.9-13.6%, DPPH; and 8.5-29.7%, ORAC) contribution to antioxidant activities when compared to the coffee leaf extracts. We conclude that the solvent polarity is particularly important to the unique phytochemical mixture recovered, which in turn governs the bioactivity. This study also demonstrated that other phytochemicals in coffee leaves that were not measured in this study are important in assessing total antioxidant activity of this potential plant beverage.