Flavonoid from Moringa oleifera leaves revisited: A review article on in vitro, in vivo, and in silico studies of antidiabetic insulin-resistant activity

Diabetes mellitus (DM) occurs when the body experiences insulin deficiency or is unable to use insulin appropriately, which increases the blood glucose levels over the threshold. Moringa oleifera leaf is a widely used and scientifically proven herbal medicine to treat DM. The demand for the development of new drugs has prompted in vitro, in vivo, and in silico studies of antidiabetic insulin-resistant activity. This study aims to conduct a comprehensive study of the types of flavonoid and nonflavonoid compounds that have antidiabetic activity in insulin resistance mellitus using in vitro, in vivo, and in silico approaches. The literature review was conducted in accordance with the offered reporting items for systematic review. Major bibliographic databases, i.e. Scopus, PubMed, and DOAJ, covering original articles about the aforementioned issues between January 1, 2011 and December 31, 2021 were used. In this study, 274 articles were retrieved, of which 4 were duplicates, and after the titles were read, only 108 were left for analysis. After the abstract screening, 32 articles were eligible for the literature review. The results exhibit that flavonoids, including quercetin and kaempferol, and nonflavonoids, including anthraquinone, cytogluside (glycoside), hemlock tannin, phenolic steroid, and 2-phenylchromenylium (anthocyanins), have potential insulin-resistant antidiabetic activity in vitro, in vivo, and in silico. This has broadened the research into the development of new drugs.