Free Radical Scavenging Activity and Total Flavonoid Content of Siamese Neem Tree Leaf Aqueous Extract from Different LocationsPongtip Sithisarn and Wandee Gritsanapan*
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Siamese neem tree (Azadirachta indica A. Juss. var. siamensis Valeton) is a medicinal plant found in every part of Thailand. Young leaves and flowers of this plant are traditionally consumed as a bitter tonic vegetable. There is a report concerning antioxidant activity of Siamese neem tree leaves including free radical scavenging activity and inhibition of lipid peroxidation in cancer cell line. Moreover, it is found that the leaves of Siamese neem tree contain some antioxidant flavonoids including quercetin and rutin. Therefore, free radical scavenging activity determination by DPPH scavenging assay and total flavonoid content analysis of the leaf aqueous extracts of Siamese neem tree collected from different locations in Thailand were performed in this experiment. It was found that Siamese neem tree leaf extracts contain total flavonoids in a range of 110.0 to 511.4 mg quercetin equivalent per 100 g extract, while EC50 values obtained from DPPH method were in a range of 28.85 to 173.77 µg/ml. The free radical scavenging activity and total flavonoid content of the extracts from different regions were significantly different (p < 0.05) and samples from the south showed the activity and flavonoid content > the north > the east > the west > the north-east > the central samples. The extract from Songkhla sample promoted both the strongest antioxidant activity (EC50, 28.85 µg/ml) and the highest total flavonoid content (511.4 mg quercetin equivalent/ 100 g extract). The results suggested that total flavonoid content in Siamese neem tree leaf extracts correlated with antioxidant activity.
Keyword:
Azadirachta indica, DPPH, free radical scavenging, Siamese neem tree, total flavonoid, Leaf Aqueous Extract
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