Polyphenols: Potential Future Arsenals in the Treatment of Diabetes

Diabetes mellitus (DM) is one of the most common endocrine metabolic disorders. In addition to exercise and diet, oral anti-diabetic drugs have been used as a part of the management strategy worldwide. Unfortunately, none of the conventional anti-diabetic drugs are without side effects, and these drugs pose an economic burden. Therefore, the investigation of novel anti-diabetic regimens is a major challenge for researchers, in which nature has been the primary resource for the discovery of potential therapeutics. Many plants have been shown to act as anti-diabetic agents, in which the main active constituents are believed to be polyphenols. Natural products containing high polyphenol levels can control carbohydrate metabolism by various mechanisms, such as protecting and restoring beta-cell integrity, enhancing insulin releasing activity, and increasing cellular glucose uptake. Blackberries, red grapes, apricots, eggplant and popular drinks such as coffee, cocoa and green tea are all rich in polyphenols, which may dampen insulin resistance and be natural alternatives in the treatment of diabetes. Therefore, the aim of this review is to report on the available anti-diabetic polyphenols (medicinal plants, fruits and vegetables), their mechanisms in the various pathways of DM and their correlations with DM. Additionally, this review emphasizes the types of polyphenols that could be potential future resources in the treatment of DM via either novel regimens or as supplementary agents.