Diabetes Mellitus is a metabolic disorder characterized by high blood glucose level caused by deficiency of insulin secretion or insulin action. Postprandial blood glucose level in patients with type II diabetes may be controlled by inhibition of alpha amylase, which is one of the carbohydrate hydrolysing enzymes. Alpha amylase is an enzyme which breaks down starch to maltose by hydrolysing alpha bonds of large, alpha-linked polysaccharides, such as starch and glycogen. Alpha amylase inhibitors may be useful as adjuvant drugs in type II diabetes. The objective of this review is to gather information regarding the identification and evaluation of alpha amylase inhibitors from natural and synthetic sources.