Research Article Evaluation of -Glucosidase Inhibitory Effect of 50% Ethanolic Standardized Extract of Orthosiphon stamineus Benth in Normal and Streptozotocin-Induced Diabetic Rats Elsnoussi Ali Mohamed, Mariam Ahmad, Lee Fung Ang, Mohd. Zaini Asmawi, and Mun Fei Yam School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia Correspondence should be addressed to Mohd. Zaini Asmawi; amzaini@usm.my and Mun Fei Yam; yammunfei@yahoo.com Received 24 May 2015; Revised 2 September 2015; Accepted 27 September 2015 Academic Editor: ierry Hennebelle Copyright © 2015 Elsnoussi Ali Mohamed et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In the present study, a 50% ethanolic extract of Orthosiphon stamineus was tested for its -glucosidase inhibitory activity. In vivo assays of the extract (containing 1.02%, 3.76%, and 3.03% of 3  hydroxy-5,6,7,4  -tetramethoxyflavone, sinensetin, and eupatorin, resp.) showed that it possessed an inhibitory activity against -glucosidase in normal rats loaded with starch and sucrose. e results showed that 1000 mg/kg of the 50% ethanolic extract of O. stamineus significantly ( < 0.05) decreased the plasma glucose levels of the experimental animals in a manner resembling the effect of acarbose. In streptozotocin-induced diabetic rats, only the group treated with 1000 mg/kg of the extract showed significantly ( < 0.05) lower plasma glucose levels aſter starch loading. Hence, -glucosidase inhibition might be one of the mechanisms by which O. stamineus extract exerts its antidiabetic effect. Furthermore, our findings indicated that the 50% ethanolic extract of O. stamineus can be considered as a potential agent for the management of diabetes mellitus. 1. Introduction Type 2 diabetes mellitus (DM) is a metabolic disease char- acterized by hyperglycemia, a condition which could either be attributed to insufficient insulin secretion or insulin resistance. e number of diabetic patients is rapidly rising in most parts of the world, especially in the developing countries such as ailand, India, and Indonesia. Controlling blood glucose levels of diabetics within the normal range is mainly based on the use of oral hypoglycemic/antihyperglycemic agents and insulin. However, these conventional treatments have undesirable side effects [1–3]. ose shortcomings have led to a great interest in the use of medicinal plants as alter- natives for the management of type 2 diabetes mellitus [4]. Control of postprandial plasma glucose levels is critical in the early treatment of diabetes mellitus and in reducing chronic vascular complications. Basically, a sudden rise in blood glu- cose levels, causing hyperglycemia in type 2 diabetic patients, would be due to starch hydrolysis by the -amylase and -glucosidases found in gastrointestinal tract [5]. Complex starches, oligosaccharides, and disaccharides must be broken down into monosaccharides (glucose and fructose) before they can be transported across the intestinal lumn (mainly in duodenum and upper jejunum) into the bloodstream and thereby increase blood glucose level. us, one of the effective strategies for the management of blood glucose level in type 2 DM is by inhibition of -glucosidases and -amylase [6, 7] which reduces the digestion of carbohydrates for pro- duction of monosaccharide and, hence, indirectly decreases blood glucose level. Among glucose lowering medications, -glucosidase inhibitors delay the absorption of ingested carbohydrates, reducing the postprandial glucose and insulin peaks [8]. It was demonstrated that -glucosidase inhibitors could be used to prevent disorders such as diabetes, obesity, hyperlipidaemia, and hyperlipoproteinaemia [9]. Our previ- ous study showed that 50% ethanolic extract of O. stamineus and its active ingredient, sinensetin, were able to inhibit - glucosidase and -amylase in vitro [10]. To the best of our knowledge, there have been no other reports on in vivo - glucosidase inhibitory activity of O. stamineus. e present Hindawi Publishing Corporation Evidence-Based Complementary and Alternative Medicine Volume 2015, Article ID 754931, 6 pages http://dx.doi.org/10.1155/2015/754931