It is well known that

It is well known that in the studies on protein structure–activity relationships, the most basic requirement is to firstly obtain the bioactive protein with high purity and then to conduct research with different means and in different aspects. One relatively important way is to directly cleave (separate) the target protein into several structural units and fragments with biochemical methods and then conduct structural measurement and functional experiments, respectively, and finally determine the structure–activity relationships as a whole. Another relatively new way is to use bioinformatics methods to compare the similarities in protein sequences and structures of the target proteins with those of many other proteins that have the similar functions, especially the structures of the known active center. Finally, the data analysis and reorganization are conducted to reveal the structure–activity relations of the target proteins. The third way is to conduct point mutations on the key amino alcohol dehydrogenase inhibitor residues or region based on protein sequences and/or three-dimensional structures to determine the structure–activity relationships of the target proteins with molecular biology methods [72]. Among three methods, the first two are commonly used by the researchers in the fields of nutrition and food sciences and also have obtained good results [73]. The third method is commonly used in researches on molecular biology, which can provide detail information about the structure–activity relationships but it is time-consuming, tidier and high-cost. It is usually used when the first two methods are failed or is used for confirming certain hypothesis.
Acknowledgements This work was supported by National Natural Science Foundation Funding (31101316; 31371805), Program for New Century Excellent Talents in University of Ministry of Education of China (NCET-11-0796) and Heilongjiang Province Postdoctoral Science Foundation.
Introduction Diabetes mellitus is a well-known metabolic disorder, which is characterized by an abnormal postprandial increase of blood glucose level. The control of postprandial hyperglycemia is believed to be important in the treatment of diabetes mellitus. α-Glucosidase secreted from intestinal chorionic epithelium is responsible for the degradation of carbohydrates. In the 1980s, α-glucosidase (EC 3.2.1.20) inhibitors became a new class of antidiabetic drug. α-Glucosidase inhibitors slow down the process of digestion and absorption of carbohydrates by competitively blocking the activity of glucosidase. Consequently, the peak concentration of postprandial blood glucose is reduced and the blood sugar level comes under control. α-Glucosidase inhibitors can offer several advantages and has been recommend by the Third Asia-Pacific Region Diabetes Treatment Guidelines as the first-line of treatment for lowering postprandial hyperglycemia [1]. α-Glucosidase inhibitors fall under the third category of oral hypoglycemic agents [2]. Several α-glucosidase inhibitors, such as acarbose and voglibose obtained from natural sources, can effectively control blood glucose levels after food intake and have been used clinically in the treatment of diabetes mellitus [3]. Only a few α-glucosidase inhibitors are commercially available. All of them contain sugar moieties and their synthesis involves tedious multistep procedures. Moreover, clinically they have been associated with serious gastrointestinal side effects. Therefore, it is necessary to search for alternatives that can display α-glucosidase inhibitory activity but without side reactions. In recent years, projects undertaken to discover potent non-sugar based α-glucosidase inhibitors from natural sources have received tremendous attention because of the highly abundant compounds in nature and their promising biological activities [4].
Research development
Conclusion Natural products are still considered as potential resources for drug discovery and play an important role in drug development programs. Moreover, many medicinal herbs are a rich source of bioactive chemicals that are remarkably free from undesirable side-effects and display powerful pharmacological actions. Compounds having α-glucosidase inhibitory activity are ubiquitous in medicinal plants. A systematic review of literature revealed that 411 compounds belonging to different structural frameworks, i.e., terpenes, alkaloids, quinines, flavonoids, phenols, phenylpropanoids, sterides, and compounds with other structural and functional motifs isolated from medicinal plants, showed potent inhibitory activity toward α-glucosidase.