Antioxidant properties and carbohydrate-hydrolyzing enzyme activities of aqueous extract from different parts of Costus afer (Ker Gawl)
摘要
This study evaluated the polyphenolic content, estimated glycemic index, antioxidant potential, and enzyme inhibitory activities of aqueous extract from different parts of Costus afer (Ker Gawl). The leaf extract exhibited the highest total phenolic content (45.87 ± 0.03 mg GAE/g) and flavonoid contents (32.39 ± 0.03 mg QE/g), while the stem showed the lowest value. The estimated glycemic index was lowest in the leaf (20.14 ± 0.035%), indicating its potential to better regulate blood glucose levels compared to the stem and rhizome. Antioxidant activities assessed using DPPH, ABTS, NO, and FRAP assays, revealed variable results. The stem and leaf demonstrated statistically similar DPPH radical scavenging abilities, while the rhizome showed the strongest FRAP activity. ABTS and NO assays highlighted the rhizome's superior free radical scavenging capacities. Additionally, the rhizome exhibited the highest inhibition of FeSO₄-induced lipid peroxidation (469.10 ± 2.67 µg/ml). The α-amylase and α-glucosidase inhibitory activities were significantly higher in all Costus afer extracts compared to acarbose. The rhizome had the strongest α-amylase inhibition (27.52 ± 0.59 mg/ml), while the stem exhibited the highest α-glucosidase inhibition (18.71 ± 0.94 mg/ml). HPLC analysis identified quercetin, caffeic acid, kaempferol, and other bioactive phenolics, with the leaf showing the highest quercetin content. These findings suggest that Costus afer extracts, particularly the leaf and rhizome, exhibit promising antioxidant, antidiabetic, and bioactive properties, supporting their potential use in managing oxidative stress and diabetes.