Alpha-Amylase Inhibitory and Antioxidant Activity of Red Galls Induced by Forda riccobonii in Pistacia atlanticaDesf. Leaves:In vitro and In silico Studies

Abstract

Pistacia atlantica has been widely used as a herbal remedy in the Mediterranean and the Middle East since antiquity. P. atlantica has been  used as an antidiabetic drug plant in Arabic folk medicine. This study aims to determine the hypoglycemic and antioxidant activities  of the gall part induced by Forda riccobonii in P. atlantica leaves from Algeria. Hypoglycemic activity was determined by  measuring alpha-amylase inhibition activity using spectrophotometric analysis of extracts. Antioxidant activity was determined by DPPH,  ABTS scavenging assay and FRAP reducing assays. A molecular docking study was carried out on compounds previously isolated from  leaves using AutoDock vina software. The highest total phenolic content (655.49±18.36 mg GAE/g DM) and flavonoid content  (381.30±15.47 mg QE/g DM) were detected in the butanol fraction. Based on the DPPH assays the ethyl acetate and butanol fractions had  high antioxidant activities with EC₅₀ 2.46 and 9.94 µg/mL respectively. According to the ABTS assay, the best antioxidant activities were  for the 35% MeOH-H₂O (4.22 µg/mL) and ethyl acetate fractions (7.23 µg/mL). The α-amylase inhibitory activity was highest in the ethyl  acetate fraction (IC₅₀ 64.53±2.50 µg/mL) followed by the positive control acarbose (78.98±6.23 µg/mL) and butanol fraction, (151.85±3.01  µg/mL). The in silico study of compounds 5,6,7,4'-tetra-hydroxy-flavonol3-O-rutinoside and 3',5,7-tri-hydroxy-4'-methoxy-flavanone gave  the best docking score (-8,3491 Kcal/mol and -8,1583 Kcal/mol, respectively). Finally, the in silico studies have confirmed significant α- amylase inhibitory activity with these molecules. As well as, the ADMET properties of these molecules appeared to be non-carcinogenic  and non-hepatotoxic. Therefore, the gall's extract of P. atlantica could be used in the treatment of diabetes.