Structure-Activity Relationships of Natural and Synthetic Indole-Derived Scaffolds as α-Glucosidase Inhibitors: A Mini-Review

α-Glucosidase plays an important role in carbohydrate metabolism and is an attractive drug target for the treatment of diabetes, obesity and other related complications. Currently, acarbose, miglitol and voglibose have been approved by the FDA for the treatment of diabetes by oral α-glucosidase inhibitors. With the development of anti-diabetic drugs, the emergence of novel drugs with various chemotypes has overshadowed α-glucosidase inhibitors. Since the 1990s, the FDA has not approved new chemical entities against α-glucosidase, which has resulted in restricted clinical medication. Nevertheless, this type of inhibitors possess several unparalleled advantages over other drugs, especially mild side effects (non-systemic gastrointestinal side effects and occasional allergic reactions). Additionally, α-glucosidase inhibitors for monotherapy or in combination with other drugs have been proved to be a feasible approach for the treatment of diabetes. In the last decade, the discovery of natural or synthetic indole derivatives possessing the inhibitory activity of α-glucosidase has received great attention. Herein, we have summarized indoles as inhibitors of α-glucosidase activity, their mechanism of action, synthetic methodologies and structure-activity relationships. Moreover, we have compared the inhibitory potencies of all compounds under their corresponding positive control as well as oral absorption in silico evaluated by tPSA. This review will provide a medium on which future drug design and development for the treatment of diabetes may be modeled as many drug candidates with present great potential as effective anti-diabetic chemotherapy.