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Received Feb 12, 2018; Accepted Apr 4, 2018
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1. Introduction
In recent years, the number of diabetic patients is rapidly rising in most parts of the world, especially in developing Southeast Asian countries [1, 2]. The control of blood glucose concentrations near the normal range is mainly based on the use of oral hypoglycaemic/antihyperglycaemic agents and insulin. However, all of these treatments have limited efficacy and are associated with undesirable side effects [3, 4], leading to increasing interest in the use of medicinal plants for the alternative management of type 2 diabetes mellitus. An effective suggestion for type 2 diabetes management is the inhibition of α-glucosidase and α-amylase [5].
Natural health-care products derived from medicinal plants or herbs have been developed as alternative or complementary treatments for many common disorders [6]. Several medicinal plants have been the useful sources of novel biologically active compounds. Many pharmaceutical agents have been discovered by screening natural products from plants, many of which have been developed as new leads for pharmaceuticals [7]. Predominantly herbal drugs have been widely used globally for diabetic treatment over thousands of years due to their traditional acceptability and lesser side effects. Therefore, screening of α-amylase (1,4-α-D-glucan glucanohydrolases; EC. 3.2.1.1) and α-glucosidase (α-D-glucoside glucohydrolase, EC 3.2.1.20) inhibitors in medicinal plants has received much attention [6, 7].
Among the traditionally used important medicinal plants, the genus Wedelia (Asteraceae) contains approximately 107 species in the world, and among them, about 6 species are in Vietnam. They are all herbal plants and distributed in tropical and subtropical regions of Asia and Pacific Islands [8]. Wedelia chinensis (Osbeck.) Merr. (Asteraceae) is a deciduous shrub, widely distributed in several Asian countries such as China, Japan, and mainland Vietnam. The leaves, stems, and fruits of this species have been traditionally used in fold medicine for the treatment of chin cough, diarrhoea, diphtheria, faucitis, hemorrhoids, and injuries due to falls, jaundice, and pertussis and are often consumed as tea in the form of infusion [9]. Phytochemically, up to date, a number of secondary...