Assessment of the α-glucosidase and α-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 α- amylase and α- 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. α- amylase and α- glucosidase inhibitory effect studies were conducted to prove this effect. The n -hexane sub-extract of the methanolic fruit extract (IC 50 = 445.7 ± 8.5 µg/mL) showed greater inhibitory activity against α -glucosidase than acarbose (IC 50 = 4212.6 ± 130.0 µg/mL), in contrast to its slight/no inhibitory effect on α -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 ( β -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 (IC 50 = 248 ± 12 µM) showed higher α -glucosidase inhibitory activity than acarbose (IC 50 = 6561 ± 207 µM). As extracts, the compounds were also found to be ineffective against α -amylase. Graphical abstract Highlights P. spina christi fruit extract were investigated for their hypoglycemic effects. Three triterpenes, namely betulin (1a) , betulinic acid (1b) , and lupeol (2) were isolated. One sterol, β -sitosterol (3) , was isolated. Compounds 1a , 1b , and 2 were isolated from this species for the first time. Betulin and betulinic acid were found to be responsible for the hypoglycemic activity of this species.