Abstract

• The present research deals with chemical structure and some biological activities relationship of isolated flavonoids from some medicinal plants. Three flavonoids, namely luteolin 1, dihydroquercetin 7,4-dimethyl ether 2 have been isolated from the peel of Citrus maxima (Burm.) Marr; naringenin 3 is obtained from Peltophorum pterocarpum (DC.) K. Heyne flower. Their structures were comparatively confirmed by UV, chemical test and co-TLC with their respective standards. Their biological activities were evaluated for antioxidant properties using the DPPH assay, α-amylase and α-glucosidase inhibition in vitro, and in vivo hypoglycemic effects in an alloxan-induced diabetic mice model. The antioxidant effects of flavonoids 1, 2, and 3 by DPPH assay were IC50 values 1.5 M, 9.4 M, and 27.7 M, respectively. Luteolin (1) exhibited the most potent antioxidant, α-amylase, and α-glucosidase inhibitory activities. In vivo, luteolin (1) also demonstrated significant hypoglycemic effects. This study suggests that flavonoids with hydroxyl groups at C-5 and C-7 in ring A, a carbonyl oxygen at C-4, a double bond between C-2 and C-3 in ring C, and hydroxyl groups at C-3' and C-4' in ring B are likely to possess potent antioxidant and antidiabetic activities.