Antioxidant and α-Glucosidase Inhibitory Constituents from Hornstedtia Species of Malaysia

Abstract

Seven compounds were isolated from the n-hexane and chloroform extracts of the flowers and leaves of four Hornstedtia species and their structures were identified using spectroscopic techniques as 3,7,4′-trimethylkaempferol (1), 3,7-dimethylkaempferol (2), 7,4′-dimethylkaempferol (3), 3,5-dimethylkaempferol (4), 3-methylkaempferol (5), stigmast-4-en-3-one (6), and 6-hydroxy-stigmast-4-en-3-one (7). Compounds 1 to 7 were isolated from these species for the first time. They were assayed for free radical scavenging and α-glucosidase inhibition activities. The DPPH assay showed that 3-methylkaempferol (5) was the most potent antioxidant agent with an IC₅₀ value 78.6 μM, followed by 7,4′-dimethylkaempferol (3) (IC₅₀ = 86.1 μM). For α-glucosidase inhibition activity, 3-methylkaempferol (5) exhibited significant inhibitory activity with an IC₅₀ value 21.0 μM. The present study revealed that Hornstedtia species have potential activities as antioxidant and α-glucosidase inhibitors.