Assessment of the alpha-glucosidase and alpha-amylase inhibitory potential of Paliurus spina-christi Mill. and its terpenic compounds

Type II diabetes mellitus is a common disease in the world and characterized by hyperglycemia. Prevention of diabetes by reducing hyperglycemia depends on the inhibition of alpha-amylase and alpha-glucosidase enzymes. In this study, the antidiabetic profiles of the Paliurus spina-christi Mill. fruit were investigated. The fruit of this species is used as an antidiabetic in folk medicine in Turkey. alpha-amylase and alpha-glucosidase inhibitory effect studies were conducted to prove this effect. The n-hexane sub-extract of the methanolic fruit extract (IC50 = 445.7 +/- 8.5 mu g/mL) showed greater inhibitory activity against alpha-glucosidase than acarbose (IC50 = 4212.6 +/- 130.0 mu g/mL), in contrast to its slight/no inhibitory effect on alpha-amylase. The phytochemical investigation of the n-hexane sub-extract of the P. spina-christi fruit led to the isolation of three triterpenes, namely betulin (1a), betulinic acid (1b), and lupeol (2), and a sterol (beta-sitosterol) (3). The structures of compounds 1-3 were further analyzed using extensive 1D- and 2D-NMR, and the results were compared with literature. Betulin (1a), betulinic acid (1b), and lupeol (2) are reported from this species for the first time. All the isolated compounds, especially betulin (1a) and betulinic acid (1b) mixture (IC50 = 248 +/- 12 mu M) showed higher alpha-glucosidase inhibitory activity than acarbose (IC50 = 6561 +/- 207 mu M). As extracts, the compounds were also found to be ineffective against alpha-amylase.