| Popis: |
Background: We investigated Juniperus Phoenicea (J. Phoenicea) and Calicotome Villosa (C. Villosa) from Jordan for phenolic contents, antioxidant, anti β-Galactosidase activities, in an attempt to rationalize its use in lactose metabolism disorders. The kinetic parameters of leave extracts, galactose, glucose, fructose and acarbose were evaluated. Also, the thermodynamic parameters of the enzyme thermal inactivation were determined. Methods: JP and cv crude methanolic extracts were evaluated for 1,1-diphenyl,2-picrylhydrazyl (DPPH) free radical scavenging activity and ferric reducing antioxidant power (FRAP). Further, β-Galactosidase inhibitory activities were performed using O-nitrophenyl-beta-D-galactopyranoside as substrate. Moreover, total phenolic contents, flavonoids and flavonols of plants extracts were determined and expressed in mg of gallic acid equivalent (mg GAE/g dry extract) or rutin equivalent per gram of dry extract (mg RE/g dry extract).Results: Phytochemical screening of the crude extract of J. Phoenicea and C. Villosa leaves contained phenols, alkaloids, flavonoids, terpenoids, anthraquinones and glycosides. J. Phoenicea exhibited high flavonoids and flavonols contents than C. Villosa but both J. Phoenicea and C. Villosa contained high phenolic and showed concentration dependent DPPH scavenging activity, with J. Phoenicea (IC50 =11.1 μg/ml), C. Villosa (IC50 =15.6 μg/ml), respectively. According to FRAP assay, the antioxidant power activity of plants extracts was concentrations dependent. The β-galactosidase % inhibition was increased as the concentration of of J. phoenicea, C. villosa and rutin increased. The mode of inhibition of β-galactosidase by J. phoenicea (IC50= 65 µg/ml) and C. villosa (IC50= 700 µg/ml) extracts was non-competitive and mixed-inhibition, respectively. Also, rutin was affected in a competitive (IC50 = 75 µg/ml) inhibition. β-galactosidase half-life was 108 min at 55°C, thermodynamic parameters revealed an activation energy of 208.88 kJ mol-1 and the inactivation kinetic follows a first-order reaction with k-values ranges between 0.0862 and 0.0023 min-1. The enzyme showing a decreasing trend of enthalpy of denaturation (∆H°) as temperature increase but value of free energy of thermal denaturation (∆G°) for β-galactosidase was decreased with increasing in temperature. The calculated entropy of inactivation (∆S°) at each temperature showed positive values, which means there are no significant processes of aggregation.Conclusions: J.phoenicea and C.villosa have inhibiting effect on β-galactosidase activity. Thermodynamic approach shows an enzyme stable and suggests that inactivation mechanism is based on molecular structural changes. |
