Poncirus trifoliata (L.) Raf.: chemical composition, antioxidant properties and hypoglycaemic activity via the inhibition of alpha-amylase and alpha-glucosidase enzymes.

The aim of this study was to investigate the phytochemical content of Poncirus trifoliata (L.) Raf. (Rutaceae) and to assess its hypoglycaemic and antioxidant effects. Hesperidin, naringin and chlorogenic acid were the most abundant compounds of the juice. Peel essential oil showed that limonene, myrcene, p-cimene and β-pinene were its main components. The antioxidant activity was studied through different in vitro tests. The hypoglycaemic effects were analysed via inhibition of carbohydrate-hydrolysing enzymes. IC50 values in the range 30.38–39.25 microg/mL were found respectively for juice and peel oil in the DPPH test. Juice inhibited α-amylase and α-glucosidase with IC50 values respectively of 138.14 and 81.27 microg/ mL. Polyphenolic compounds identified in the juice were investigated. While neoeriocitrin displayed the strongest antioxidant activity and inhibited α-amylase (IC50 of 4.69 vs 77.45 microM for acarbose), didymin was found to be the most bioactive flavonoid against alpha-glucosidase (IC50 of 4.20 vs 54.99 microM for acarbose).