Medicinal plants as protectants against zinc toxicity in aquatic and terrestrial life: A review

Abstract

Zinc is a vital trace element that takes part in various biological functions such as enzyme activity, immune response and metabolism of the cells but excessive exposure leads to acute toxicity among aquatic and terrestrial species such as fish, animals and humankind. High zinc levels interfere with metal ion homeostasis, stimulate the formation of reactive oxygen species, inhibit antioxidant defense systems and cause cellular and molecular damage that eventually results in physiological dysfunction and disease. The growing industrialization, agricultural effluents, environmental pollution and over-supplementation have increased the concern of the world on zinc induced toxicity in the environmental and biological systems. The ability of medicinal plants to prevent heavy metal toxicity has seen the development of medicinal plants as potential natural protective agents because of their good phytochemical compounds and multifunctional biological properties. The review is a critical evaluation of experimental studies, which illustrate the protective properties of medicinal plants against zinc induced toxicity amongst aquatic and terrestrial organisms. Special attention is given to the mechanistic actions of bioactive compounds of plant origin, such as antioxidant, metal chelation, regulation of inflammatory and apoptotic processes, and cellular redox regulation and homeostasis. The botanicals with reference to their mitigation of zinc associated oxidative stress, tissue damage, and functional impairment are discussed using medicinal plants like Withania somnifera, Curcuma longa, Allium sativum, Ocimum basilicum, Ginkgo biloba and Salvadora persica. The review indicates the promise of medicinal plants as complementary and sustainable measures of controlling zinc toxicity with a view of solving the challenges that exist regarding standardization, optimization of doses, safety and translational applicability. Their potential therapeutic effectiveness and relevance to the environment needs to be confirmed in further mechanistic exploration and in the long term.