COMPARATIVE AND SYNERGISTIC ANTIOXIDANT PROPERTIES OF CARICA PAPAYA AND AZADARICHTA INDICA LEAVES

Comparative and synergistic antioxidant properties of Carica papaya leaf (CPL) and Azadarichta indica leaf (AIL), which are popularly used as medicinal plants were evaluated by analyzing the individual leaves and their 1:1 (mass/mass) homogenous combination (CPL+AIL) concurrently. The antioxidant properties measured were the levels of total phenol, tannin, total flavonoid, total carotenoid, vitamin C, 1,1-diphenyl-2-picrylhydrazyl (DPPH) free-radical scavenging ability, trolox equivalent antioxidant capacity (TEAC) and ferric reducing antioxidant power (FRAP). Of the two plants, AIL had significantly higher (P < 0.05) total phenol and tannin contents, as well as  significantly higher (P < 0.05) DPPH scavenging ability, TEAC and FRAP, while CPL had significantly higher (P < 0.05) total flavonoid, total carotenoid and vitamin C contents. The combination (CPL+AIL) showed a synergy in the total phenol, tannin, total flavonoid, and total carotenoid contents, and in the DPPH free radical scavenging ability.  The DPPH scavenging ability of the leaves increased in a dose-dependent manner, having IC₅₀ in the order of APL< CPL+AIL< CPL [APL (0.50 mg/ml), CPL+AIL (0.61 mg/ml), CPL (0.93 mg/ml)]. The combination further showed an additive synergistic interaction in the TEAC and FRAP in the order of CPL+AIL > APL > CPL. However, there was a negative synergistic interaction in the vitamin C content. The study therefore concludes that while AIL has better antioxidant activities than CPL, the combination of CPL and AIL produces synergistic antioxidative interactions, which could be explored in their medicinal uses.