Antioxidant potential of spices and their active constituents.

Excessive free radical generation overbalancing the rate of their removal leads to oxidative stress. Oxidative stress has been implicated in the etiology of cardiovascular disease, inflammatory diseases, cancer, and other chronic diseases. Antioxidants are compounds that hinder the oxidative processes and thereby delay or suppress oxidative stress. There is a growing interest in natural antioxidants found in plants. Herbs and spices are most important targets to search for natural antioxidants from the point of view of safety. A wide variety of phenolic compounds present in spices that are extensively used as food adjuncts possess potent antioxidant, anti-inflammatory, antimutagenic, and cancer preventive activities. This paper reviews a host of spice compounds as exogenous antioxidants that are experimentally evidenced to control cellular oxidative stress, both in vitro and in vivo, and their beneficial role in preventing or ameliorating oxidative-stress-mediated diseases, from atherosclerosis to diabetes to cataract to cancer. The antioxidative effects of turmeric/curcumin, clove/eugenol, red pepper/capsaicin, black pepper/piperine, ginger/gingerol, garlic, onion, and fenugreek, which have been extensively studied and evidenced as potential antioxidants, are specifically reviewed in this treatise.