Influence of Extraction Solvents on Cosmos caudatus Leaf Antioxidant Properties

Cosmos caudatus is commonly used as a medicinal plant in tropical countries. C. caudatus leaf extracts were obtained using five different extraction solvents, namely 100 % methanol, 100 % ethanol, 95 % ethanol, 50 % ethanol, and 100 % water. Mechanically liberated C. caudatus leaf juice was also used for comparison. The total carotenoid content, total phenolic content, total flavonoid content, DPPH, ABTS, FRAP and β-carotene bleaching assays of the extracts were determined spectrophotometrically, while ascorbic acid content was quantified using HPLC. Among all the CC leaf extracts, water extracts exhibited the highest total phenolic content (10,513 mg GAE/100 g fresh sample), total flavonoid content (1654.7 mg/100 g fresh sample), and ascorbic acid content (153.7 mg/100 g fresh sample). While the 100 % methanol and 50 % ethanol extracts of C. caudatus leaves demonstrated the highest antioxidant activities as assessed using DPPH, ABTS and FRAP. The highest total carotenoid content was observed in the methanol extract of C. caudatus leaves. C. caudatus leaf juice contained the lowest ascorbic acid, TPC, TFC and antioxidant activities. Overall, using different types of extraction solvents had significant effects on the antioxidant properties of the extracts. 50 % ethanol was subsequently recommended as the most efficient solvent to extract antioxidant compounds from C. caudatus leaf.