Alpha amylase inhibition and antioxidant potential of Raphia hookeri (Palmae)

摘要

This study was carried out to investigate a-amylase inhibitory and antioxidant activities of extract and fractions of Raphia, hookeri stembark. The results showed that the extract prevented the digestion of starch by inhibiting a-amylase in a dose dependent manner with maximum inhibitory ef-fect (72.86 %, 1.00 mgml~(-1). The aqueous fraction demonstrated highest inhibition (67.22%, 0.50 mgml~(-1)) which was less than acarbose (68.90%, 0.08 mgml~(-1)) used as positive control. The hexane, chloroform and ethylacetate fractions showed lower inhibitory activity (12.16, 9.06, 35.97%) respectively. The total phenolic content of the R. hookeri extract measured using Folin Ciocalteu reagent in terms of gallic acid equivalent (GAE) was found to be 109:10 ±3.24 mgg~(-1). The antioxidant activity of the extract increased with concentration and the aqueous fraction produced the highest radical scavenging effect (95.04 ± 0.57%, 0.10 mgml~(-1)) which was significantly less (P < 0.05) that of ascorbic acid. The hexane, chloroform and ethylacetate fractions however demonstrated lower radical scavenging activity (18.4, 11.1 and 94.9 %) respectively. The reducing ability of the extract was comparable to that of ascorbic acid and the aqueous fraction produced the best activity. This study indicates that the extract of Raphia hookeri has a-amylase inhibitory and antioxidant activities which reside mainly in ethylacetate and aqueous fractions.