Recent advances on anti-diabetic potential of pigmented phytochemicals in foods and medicinal plants

Type 2 diabetes is marked by elevated blood sugar levels and linked to impaired insulin secretion and resistance to insulin. Researchers are continuously investigating different classes of phytochemicals including natural pigments for their potential direct or indirect advantages in the prevention and/or control of diabetes. In this review, clinical trials, animal studies, and cell culture models, as well as in vitro enzyme inhibition assays and in silico molecular docking studies were covered for pigmented phytochemicals including anthocyanins, carotenoids, betalains, chlorophylls, curcumin, and phycocyanins. Recent research has shown that the anti-diabetic effects of pigments include (1) inhibition of ROS formation, (2) downregulation of inflammatory response like inhibiting COX, or regulation of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6), (3) regulation of multiple signal pathways such as NF-κB, AMPK, MAPK, (4) inhibition of cell apoptosis, according to the ratio of Bcl-2/Bax; and cell proliferation via PI3K/Akt pathways, and (5) digestive enzyme inhibition, such as α-amylase and α-glucosidase, among others.