Type 2 diabetes (adult onset diabetes) is the most common type of diabetes, accounting for around 90% of all diabetes cases with insulin resistance and insulin secretion defect. The key goal of anti-diabetic therapy is to increase the development of insulin, immunity and/or decrease the amount of blood glucose. While many synthetic compounds have been produced as anti-diabetic agents, due to their side effects and limited effectiveness, their usefulness has been hindered. This systematic review investigated the bioactive compounds reported to possess activities against type 2 diabetes. Three (3) databases, PubMed, ScienceDirect, and Google Scholar, were searched for research articles published between January 2010 and October 2020. A total of 6464 articles were identified, out of which 84 articles were identified to be eligible for the study. From the data extracted, it was found that quercetin, Kaempferol, Rosmarinic acid, Cyanidin, Rutin, Catechin, Luteolin, and Ellagic acid were the most cited bioactive compounds, which all falls within the class of polyphenolic compounds. The major sources of these bioactive compounds include citrus fruits, grapes, onions, berries, cherries, broccoli, honey, apples, green tea, Ginkgo biloba, St. John's wort, green beans, cucumber, spinach, tea, Rosmarinus officinalis, Aloe vera, Moringa oleifera, tomatoes, potatoes, oregano, lemon balm, thyme, peppermint, Ocimum basilicum, red cabbage, peas, olive oil, and walnut. In conclusion, the data collected in our study indicates that consumption of polyphenolic/flavonoids rich food and vegetables as a routine diet could considerably reduce the risk of T2DM and also benefits insulin sensitivity and other chronic inflammations.
