Biological properties of monomeric and polymeric catechins: Green tea catechins and procyanidins

There is an increasing interest in the disease preventing and/or therapeutic properties of green tea and red wine. Major biologically active constituents in green tea and red wine are tea catechins and procyanidins, respectively. Tea catechins are monomers of flavan-3-ol, and procyanidins are polymers of the flavan-3-ol units such as catechin and epicatechin. These structurally related catechin compounds have extensively been studied for their various biological activities. Tea catechins and procyanidins are known as very strong antioxidants, which can scavenge various forms of free radicals. They may prevent cardiovascular diseases, probably through their ability to inhibit oxidation of low-density lipoprotein (LDL), to lower the plasma cholesterol level, and to prevent platelet aggregation. In addition, there is increasing evidence of the cancer chemopreventive properties of catechins and procyanidins. Understanding the molecular and cellular mechanisms of their beneficial properties, in particular their roles in the signal transduction pathways and gene expression, are of interest. This review discusses our current knowledge and understanding of the biological activities of tea catechins and procyanidins, including their basic chemistry, occurrence, antioxidant activity, effect on heart disease, and effects on signal transduction pathways. Together, these may provide better insights into their possible beneficial effects in human.