Antioxidant and ?-Glucosidase Inhibitory Activities of Dolichandrone serrulata Extracts

Abstract

Dolichandrone serrulata (Bignoniaceae) is used as a vegetable and food ingredient by the local people in the northern and eastern parts of Thailand. The antioxidant and α-glucosidase inhibitory activities of D. serrulata extracts were investigated. Three parts of D. serrulata (the flowers, leaves and pods) were extracted using water and 95% ethanol. The antioxidant activity of the extracts was examined by DPPH, ABTS and FRAP assays. The total phenolic content (TPC) and total flavonoid content (TFC) were determined by the colorimetric method. The αglucosidase inhibition assay was used to evaluate the in vitro anti-diabetic activity of the extracts. Results revealed that the extracts contained phenolic compounds and flavonoids. Aqueous pod extracts had the highest TPC and TFC (0.245 ± 0.020 mg GAE/g and 0.1102 ± 0.0033 mg QE/g, respectively), while aqueous leaf extracts had the highest antioxidant capacity against DPPH and ABTS (IC50 = 0.12 ± 0.020 and 0.05 ± 0.006 mg/mL, respectively). Ethanol leaf extracts had the highest FRAP value (0.988 ± 0.236 mg TE/g), while ethanol pod extracts had the highest α-glucosidase inhibitory activity (IC50 = 0.041 ± 0.002 mg/mL). In conclusion, aqueous pod extracts from D. serrulata displayed the highest TPC and TFC and antioxidant capacity against DPPH and ABTS, while ethanol leaf extracts had the highest antioxidant activity by FRAP assay. Fruit pod ethanol extracts exhibited α-glucosidase inhibitory activity, suggesting preliminary anti-diabetic activity possibly due to high phenolic and flavonoid contents.