Hypoglycemic Effect and Mechanism of Polysaccharides from Finger Citron from Guangdong Province Based on Enzyme Activities and Cell Model

Finger citron (Citrus medica ‘Fingered’) is a medicinal and edible plant belonging to the genus Citrus of the family Rutaceae. Finger citron grown in Guangdong is called Guang Foshou. The present study explored the in vitro hypoglycemic activity and mechanism of polysaccharides extracted from Guang Foshou by measuring enzyme activities as well as using cell model. The results showed that the half-maximal inhibitory concentrations (IC₅₀) of the polysaccharide fraction FCP-2-1 for α-glucosidase, α-amylase and angiotensin converting enzyme (ACE) were 2.74, 0.87 and 0.85 mg/mL, respectively. All the polysaccharides remarkably promoted glucose transport in 3T3-L1 adipocytes, improved lipid metabolism and reduced the secretion of tumor necrosis factor (TNF)-α. The mechanism might be that FCP-2-1 could promote the expression of phosphatidylinositol 3-kinase (PI3K), glucose transporter 4 (GLUT4), protein kinase B (PKB or AKT) and phosphorylated AKT (p-AKT) in the PI3K/AKT signaling pathway to alleviate insulin resistance and restore normal cellular metabolism.