Bioactive phytochemicals with emphasis on dietary practices.

Diet can modify the pathophysiological processes of various metabolic disorders and can be an effective preventive strategy for various disease processes most of which are known to involve oxidative damage. Both nutrient and non-nutrient components of the diet have been recognized for their anti-oxidant and other potential benefits. Plant foods contain phytochemicals such as flavonoids, phenolic acids, etc., which show biological activity. Some common foods used in Indian culinary practices were assessed for their anti-oxidant, anti-mutagenic and anti-carcinogenic effects and vitamin D activity and evaluated for their plausible biological effects. Green leafy vegetables had the highest anti-oxidant activity followed by wheat and rice. Cooking decreased this activity. Eugenol, the active principle of clove, was shown to offer protection against CCl4 induced hepatotoxicity in rats. It also showed anti-peroxidative activity in addition to decrease in O2 formation. Studies on the anti-carcinogenic effect of turmeric/curcumin revealed that both are potent anti-mutagens in vivo and reduce the adducted DNA levels in liver of rates challenged with B(a)P. In another study, Syrian hamsters receiving turmeric/curcumin through diet or local paint on cheek pouch had lower tumour burden as well as adducted DNA level against 7-12-DMBA challenge. Turmeric/curcumin were found to be better anti-tumour agents when given in the post initiation phase of carcinogenesis. The beneficial effect of turmeric was found to be due to its anti-oxidant potential. Studies on humans at risk of palatal cancer due to reverse smoking showed that turmeric (1 g/day) for 9 months had a significant impact on the regression of precancerous lesions. Onion and garlic also possess anti-mutagenic principle. Further studies on the bioactive phytochemicals in plants showed that certain plants belonging to Solanaceae (Cestrum diurnum, Lycopersicon esculentum and Solanum melongena) have calcinogenic potential and vitamin D like activity. In view of the vast data on bioactive principles from plants, it is suggested that dietary prevention coupled with other life-style changes in perhaps the right answer for prevention of cancer and other chronic diseases in India.