Water fraction of edible medicinal fern Stenochlaena palustris is a potent α-glucosidase inhibitor with concurrent antioxidant activity

This study aimed to isolate a potent antiglucosidase and antioxidant fraction from Stenochlaena palustris. Extraction was performed with hexane, chloroform, ethyl acetate, methanol, and water. Antiglucosidase, 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging and ferric reducing antioxidant power (FRAP) assays found methanol extract (ME) to be the most active. Water fraction (WF) of ME was a stronger alpha-glucosidase inhibitor (EC50 2.9 mu g/mL) than quercetin, with weak antiamylase activity. WF was a competitive alpha-glucosidase inhibitor. DPPH scavenging activity of WF (EC50 7.7 mu g/mL) was weaker than quercetin. WF (EC50 364 mu g/mL) was a stronger hydrogen peroxide scavenger than gallic acid (EC50 838 mu g/mL) and was equally strong as quercetin in scavenging superoxide. WF possessed moderate copper chelating activity. WF was enriched in total phenolics (TP) and hydroxycinnamic acids (THC). TP correlated with antioxidant activity (R-2 > 0.76). Only THC correlated with antiglucosidase activity (R-2 = 0.86). Overall, WF demonstrated concurrent, potent antiglucosidase and antioxidant activities. (C) 2015 Elsevier Ltd. All rights reserved.