Free radical scavenging activity of extracts from Cajanus cajan (L.) Millsp.

The antioxidant activity of Pigeon pea (Cajanus cajan) has been investigated mostly in leaf and pod extracts. The research was to investigate the potency of various plant parts including root, stem, leaf and seed from pigeon pea collected from Khonkaen Province, Thailand. Different solvents, including ethanol, dichloromethane and water, have been used to prepare plant extracts. The extracts were analyzed for total phenolic content and antioxidant capacities. The 2,2-Diphenyl-1-picrylhydrazyl (DPPH) assay, 2,2'-azinobiz(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay and Ferric reducing antioxidant power assay (FRAP assay) were used to analyze the antioxidant capacity. The total phenolic contents in ethanol, dichloromethane and water extracts were 0.870 – 4.408, 0.222 – 2.833 and 0.778 – 3.972 mg GAE/1 mg extract, respectively. Ethanol extract from stems showed the highest total phenolic content (4.408 mg GAE/1 mg extract) and also exhibited high antioxidant capacity by ABTS assay (IC₅₀= 1.119 mg/mL). The highest antioxidant capacity (IC₅₀= 0.141 mg/mL) examined by DPPH assay was observed in the seed ethanol extracts. However, the highest antioxidant capacity by FRAP assay (IC₅₀= 26.653 µg vitamin/1 mg extracts) was found in water leaf extracts.

The results indicated that the ethanol extracts from Cajanus cajan showed the highest antioxidant capacity in comparison to those from other solvents, suggesting their potency for nutraceutical and therapeutic applications.