Heavy Metals Alter the Potency of Medicinal Plants

Abstract

There has been increased use of herbal drugs in recent years. Because of increasing demand and wider use, it is essential that the quality of plant-based drugs should be assured prior to use. When heavy metals contaminate the plants from which herbal drugs are derived, they affect both plant growth characteristics and production of secondary plant metabolites. Plants exposed to heavy metal stress show changes in production of secondary metabolites. High levels of heavy metal contamination in medicinal or other plants may suppress secondary metabolite production. Alternatively, the presence of heavy metals in medicinal plants may stimulate production of bioactive compounds in many plant species. Moreover, some research results suggest that heavy metals may play an important role in triggering plant genes to alter the titers or nature of secondary plant metabolites, although the exact mechanism by which this happens remains unclear. Oxidative stress induced by heavy metals triggers signaling pathways that affect production of specific plant metabolites. In particular, reactive oxygen species (ROS), generated during heavy metal stress, may cause lipid peroxidation that stimulates formation of highly active signaling compounds capable of triggering production of bioactive compounds (secondary metabolites) that enhances the medicinal value of the plant. As usual, further research is needed to clarify the mechanism by which heavy metals induce responses that result in enhanced secondary metabolite production.

Pb and Cd on growth, leaf ultrastructure and essential oil yield mint (Mentha arvensis L.)

“…Changes in essential oil composition by heavy metals stress are associated with inactivation of specific enzymes of metabolic pathways of secondary metabolites (NASIM & DHIR, 2010). As there were no changes on M. arvensis essential oil yield and composition, probably Pb and Cd applied in the soil was not sufficient to affect these routes of secondary metabolites production.…”

“…Plants exposed to heavy metal stress show changes in production of secondary metabolites, either suppressing or stimulating production (NASIM & DHIR, 2010). Changes in essential oil composition by heavy metals stress are associated with inactivation of specific enzymes of metabolic pathways of secondary metabolites (NASIM & DHIR, 2010).…”

“…High concentrations of this metal can interfere with plant growth as well as morphological and ultrastructural aspects of its organs (TUNG & TEMPLE, 1996). Medicinal plants exposed to heavy metals can differ in production of secondary metabolites, either suppressing or stimulating production (NASIM & DHIR, 2010).…”

Establishing the botanical identity of plant drugs based on their active ingredients under diverse growth conditions

“…The reactive oxygen species (ROS) generated due to heavy-metal stress often causes lipid peroxidation, which facilitates formation of highly active signalling compounds capable of triggering the production of secondary metabolites (Nasim and Dhir, 2010). In a study of heavy metal stress on artemisinin accumulation in the leaves of , lead stress dropped the artemisinin content from 464μg g dw (control) to 226μg g dw (with 100 ppm Pb), 180 μg g (with 250 ppm Pb) and 173 μg g dw (with 500 ppm Pb), showing a general decline of artemisinin content with increase in the level of Pb applied (Qureshi ., 2005 …”

Impact of Abiotic Elicitors on In vitro Production of Plant Secondary Metabolites: A Review

“…Chemical Elicitors: Metals are influenced to alter the production of secondary metabolites by changing the aspects of secondary metabolism [11]. Metals have become one of the main abiotic stress agents for living organisms because of their increasing use in the developing fields like industry, agrotechnics, high bioaccumulation and toxicity [12].…”