Plant extracts and isolated compounds reduce parameters of oxidative stress induced by heavy metals: An up-to-date review on animal studies.

BACKGROUND: Heavy metals are elements that are naturally found in the earth. They are used in many modern-day applications, in agriculture, medicine, and industry. Heavy metal poisoning occurs when body's soft tissues absorb too much of a particular metal. The heavy metals of interest for this review paper were cadmium, arsenic, mercury and lead, since these are the most common metals that the human body can absorb in toxic amounts. Different plant species were investigated in recent years for their effect on oxidative stress parameters after intoxication with heavy metals. OBJECTIVES: This review paper is focused on current update to research on heavy metals induced oxidative stress in animal models and improvement of the oxidative stress parameters upon/co-/after treatment with different plant extracts and isolated compounds. RESULTS: Various parameters of oxidative stress were investigated and their improvement with plant extracts/compounds was noticed in the brain, lungs, kidneys, liver, uterus, testis, thymus, spleen, heart, skin and blood of experimental animals. Common parameters used to determine oxidative stress in animals were: superoxide dismutase; catalase; reduced glutathione; glutathione reductase; glutathione-S-transferase; glutathione peroxidase; lipid peroxidation; oxidized glutathione; malondialdehyde; xanthine oxidase; nonprotein-soluble thiol; thioredoxin reductase; total sulphydryl group; nitric oxide; gamma-glutamyl cysteine synthetase. CONCLUSIONS: The most investigated species for antioxidant effects upon intoxication with heavy metals seem to be Allium sp., Bacopa monniera, Camellia sinensis, Moringa oleifera, Vitis vinifera and Zingiber officinale. According to literature data, the most promising effect to alleviate symptoms of intoxication was achieved with proanthocyanidins obtained from Vitis vinifera.