Iraqi medicinal plants: Total flavonoid contents, free-radical scavenging and bacterial beta-glucuronidase inhibition activities

Abstract

Water-soluble extracts from 12 traditional Iraqi medicinal plants and herbs were investigated for their abilities to scavenge the free radicals and to inhibit the activity of the bacterial enzyme, β-glucuronidase. The extracts were determined for the total flavonoid content by using aluminum chloride colorimetric assay. The phytochemical analysis revealed that the total flavonoid content (TFC) of the aqueous extracts were in the range of 0.9-48.2 mg catechin equivalent (CA)/g dry weight (DW). DPPH-radical scavenging activity ranged from 3.4% to 80.7% with the highest activity being found in extracts prepared from Mentha piperita, while extracts from Citrulus colocynthis showed the lowest activity. In line with the variations observed in the DPPH activity, the inhibitory effect of the aqueous extracts against bacterial β-glucuronidase enzyme was also the highest in M. piperita (88.9%), while extracts from Citrulus colocynthis showed the lowest activity (14.6%). The IC50 values of the tested medicinal plants and herbs against β-glucuronidase enzyme occurred at concentrations of 0.14-3.0 mg/ml. Both DPPH-radical scavenging capacities and inhibitory effects against β-glucuronidase showed positive correlation with the TFC (R 2 = 0.4416 and 0.4653, respectively). In conclusion, our results may provide novel and useful information regarding the inhibition of microbial β-glucuronidase activity, preventing deglucuronidation and reducing possible cancer risk by crude extract from selected Iraqi medicinal plants and herbs.