Antioxidant potential, anti-proliferative activities, and phenolic content in water-soluble fractions of some commonly consumed vegetables: Effects of thermal treatment

Thermal treatments associated with food processing can alter the phenolic content of vegetables; yet, the biological properties associated with altered phenolic content have not been well delineated. We assessed the effects of various thermal treatments on total phenolic content, antioxidant and anti-proliferative activities of water-soluble fractions from six commonly consumed vegetables. Phenolic content in the water-soluble fraction of the tested vegetables was in the order of spinach > ‘komatsuna’ > ‘haruna’ > ‘chingensai’ > white cabbage > Chinese cabbage. Total antiradical activity against the DPPH radical was in the order of ‘komatsuna’ > spinach > ‘haruna’ > ‘chingensai’ > white cabbage > Chinese cabbage. Antiradical activity against hydroxyl radicals (deoxyribose assay) was highest for spinach and white cabbage. White cabbage extract showed the highest anti-proliferative activity in HL 60 cells. Normal cooking temperatures detrimentally affected phenolic content as well as antiradical and anti-proliferative activities of juice from most of the vegetables tested. However, mild heating of vegetable juices (50 °C, 10–30 min) preserved 80–100% of phenolic content, and both antioxidant activity and cell proliferation inhibition activities. The degree of thermal processing affects not only the content of phenolic compounds in vegetables but also beneficial biological effects associated with these compounds.