Effect of α‐Tocopherol, β‐Carotene, Monogalactosyldiglyceride and Phosphatidylcholine on Light‐Induced Degradation of Chlorophyll a in Acetone

Abstract

AbstractThe effect of α‐tocopherol, β‐carotene, monogalactosyldi‐glyceride and phosphatidylcholine on red light induced degradation of chlorophyll a was studied in acetone at 4°C. Monogalaclosyldi‐glyceride was ineffective up to a molar ratio of monogalactosyldi glyceride to chlorophyll of 1:10. α‐Tocopherol, β‐carotene and phosphatidylcholine inhibited chlorophyll degradation. Maximal protection by α tocopherol and β‐carotene was similar (76%) but on a molar basis a tocopherol was less effective. Protection by phosphatidylcholine was less than by a tocopherol and α‐carotene but the lipid was effective at a lower ratio of chlorophyll to protectant. Inhibition by phosphatidylcholine was independent of the degree of unsaturation of the fatty acids. Effects of β‐carotene and α‐tocopherol were additive at suboptimal concentrations, but addition did not increase the maximal protection of 76% by these substances alone. Phosphatidylcholine increased the effectiveness of α‐tocopherol and β‐carotene independent of their concentrations. It is suggested that interactions between lipids participate in the mechanism protecting chlorophyll a against photooxidation in the chloroplast membrane.