ABSTRACT
Objective: To evaluate and compare the antioxidant activity, total phenolic contents (TPCs) and in vitro antidiabetic activity of various pits extracts obtained from five Omani date cultivars. Methods: Sun-dried mature fruits of five Omani date varieties, namely, Fardh, Naghal, Khalas, Khinazi and Khasab were purchased from the local market in Muscat, Oman in the month of September 2014. Four seed extracts viz. water, ethanol, methanol and acetone were prepared for each date variety and their antioxidant activities were investigated by 1,1-diphenyl-2-picrylhydrazyl, hydrogen peroxide scavenging method and reducing power assay method, respectively. In vitro antidiabetic activity of the date pit extracts was evaluated by measuring their inhibitory effect on α-glucosidase and α-amylase level. TPCs were also quantified colorimetrically. Results: The results indicated that TPC of date seeds was solvent dependent. Acetone, ethanol and methanol were found to be significantly better solvents than water in extracting phenolic compounds from the date seeds. Pit extracts exhibited moderate to good in vitro antioxidant activity and increased reducing power. Among all date pit extracts, water extract exhibited significant in vitro antidiabetic activity in comparison to standard drug, acarbose. Conclusions: The present study confirms that disposed waste of Omani dates is a rich source of dietary antioxidant because of its high TPC. The pits due to their inhibitory effects on α-glucosidase and α-amylase level could be used as a monotherapy along with an appropriate diabetic diet and exercise or might be in conjunction with antidiabetic therapy to manage and prevent progression of diabetes.