Bioaccumulation of industrial heavy metals and interactive biochemical effects on two tropical medicinal plant species

Abstract

Concentrations of heavy metals (Cr, Cu, Fe, Mn, Ni, Pb, and Zn) accumulation were studied in the leaves of two medicinal plant species, namely Holarrhena pubescens, and Wrightia tinctoria, from two industrial areas and a control area. Our comparison study revealed that industrialization significantly increased the accumulation of heavy metals in both plant species. A comparison study in control and industrial areas exhibited that heavy metal accumulation was higher in the industrially affected area than in the control area. In the control area, both species accumulated the lowest heavy metal concentration. Where heavy metals concentration exceeded the permissible limit recommended by the WHO in both species of two industrial areas. Biochemical investigation specifies that in response to heavy metals accumulation, both species increased the activity of hydrogen peroxide (H2O2), malondialdehyde (MDA) content, the activity of enzymatic [superoxide dismutase(SOD) and peroxidase (POD)] and nonenzymatic [ascorbic acid (AsA)] antioxidant, but decreased the primary (soluble carbohydrate and total protein), secondary metabolites (phenol and flavonoid) content and free radical scavenging (DPPH) activity. These study indicate that industrialization potentially harms medicinal plants by reducing the efficacy of their medicinal property.