Quenching of singlet oxygen by D-alpha-tocopherol in human granulocytes

The ability of D-alpha-tocopherol to act as a quencher of (1)0(2) (singlet oxygen) was tested with a biological source of (1)0(2), namely the phagocytosis activated myeloperoxidase contained in the homogenate of human circulating polymorphonuclear leukocytes. With this system, the (1)0(2) quenching efficiency of exogenously added D-alpha-tocopherol was estimated from its inhibitory effect on the luminol amplified chemiluminescence. This inhibitory effect was dose dependent. D-alpha-tocopherol was also efficient in quenching the chemiluminescence generated through the H2O2-horseradish system. In both systems the quenching effect may be almost entirely "physical", since very little tocopherol was destroyed when compared to the relatively large amount of H2O2 consumed.