EFFECTS OF TANNIN AND PHENOLICS ON THE H+-ATPASE ACTIVITY IN PLANT PLASMA-MEMBRANE

The effects of the common plant antioxidants, tannin, ellagic acid and other phenolics of the cell wall metabolism on the activities of plasmalemma H+-ATPase were studied. Plasmalemma from the roots of winter wheat (Triticum aestivum L. cv. MV-8) was purified by aqueous two-phase partitioning. Tannin and ellagic acid inhibited the H+-ATPase activity with a characteristic IC50 value of 0.3 and 30 mu M, respectively. At 100 mu M concentration, (+)catechin brought about 50 % inhibition while gallic, protocatechuic, vanillic, coumaric, caffeic and ferulic acid had only slight inhibitory effects. It is concluded that the mechanism of the interaction between plant phenolic antioxidants and cell constitutents may be more composed than the formation of simple H+-bonds between phenolic-OH groups and cellular macromolecules. It is also suggested that phenolics may modify membrane transport processes in plant cells.