Planta Med 2013; 79 - PN1
DOI: 10.1055/s-0033-1352345

Alpha-amylase Inhibition and Antioxidant Activities of Methanol Extract and Fractions of Raphia hookeri (Palmae)

SA Adesegun 1, LC Osueke 1, JI Uhegbu 1, HB Coker 2
  • 1Department of Pharmacognosy, Faculty of Pharmacy, University of Lagos, Idi-Araba Campus, PMB 12003, Surulere, Lagos, Nigeria.
  • 2Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Lagos, Idi-Araba Campus, PMB 12003, Surulere, Lagos, Nigeria.

Diabetes mellitus is caused by the abnormality of carbohydrates metabolism which is linked to low blood insulin level or insensitivity of target organ to insulin. The digestion of starch by α-glucosidases contributes to sharp increase in blood glucose resulting in postprandial hyperglycemia which has been implicated in the development of type 2 diabetes. The inhibition of these enzymes is a useful tool in the management of hyperglycemia and type 2 diabetes. In this study, methanol extract of Raphia hookeri stembark and its fractions were investigated for anti-diabetic ability using in vitro α-amylase inhibitory potential. The results showed that the extract prevented the digestion of carbohydrates by inhibiting α-amylase in a dose dependent manner with maximum inhibitory effect (72.86%, 1.00 mgmL-1). The aqueous fraction demonstrated highest inhibiton (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 P. osun 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 radical scavenging activity of the aqueous fraction (93.66%, 0.10 mgml-1) was comparable to ascorbic acid (0.1 mgml-1) used as control. The hexane, chloroform and ethylacetate fractions however demonstrated lower radical scavenging activity (7.79, 8.20 and 68.30%) respectively. This study indicates that the extract of Raphia hookeri has α- amylase inhibitory and antioxidant activities which reside mainly in the aqueous fraction.

References:

[1] Kwon, Y. I., Vattem D. A., Shetty, K. (2006): Evaluation of clonal herbs of Lamiaceae species for management of diabetes and hypertension. Asia Pacific J. Clin. Nutr. 15:107 – 118.