Quantification of the nonenzymatic past and slow TRAP in a postaddition assay in human seminal plasma and the antioxidant contributions of various seminal compounds

Total radical-trapping antioxidant potential (TRAP) measurements of human s eminal plasma (N = 25) were performed by using a post-addition assay based on trapping 2,2' Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) ra dicals. This method enables the antioxidant capacity of human seminal plasm a and its constituents to be quantified. The standard procedure consisted o f determination of the Trolox equivalent antioxidant capacity (TEAC) after incubating the test sample in the ARTS radical solution for 10 seconds (fas t TRAP) and 300 s (total TRAP). Interestingly, seminal plasma showed a fast TRAP and a high slow TRAP (Total TRAP - Fast TRAP). The final total TRAP o f seminal plasma is about 10 times higher than that of blood plasma. Variou s components of seminal plasma contribute to its fast TRAP; 37% can be attr ibuted to vitamin C, uric acid, and tyrosine; proteins and polyphenolic com pounds contribute a further 57%. In contrast, the slow TRAP was attributed to vitamin C (1%), uric acid (2%), and tyrosine (15%) and to proteins and p olyphenolic compounds (33%). It was not possible to account for the remaini ng 49%. Neither known putative antioxidants, such as spermine, pyruvate, an d taurine, nor other seminal compounds, such as carnitine, sialic acid, fru ctose, spermidine, glycerophosphorylcholine, and hyaluronic acid. contribut ed to any significant radical-trapping activity at a standard concentration of 1 mM. Of the amino acids, only tyrosine possessed a slow TRAP, and it i s present at a high concentration in seminal plasma. Glutathione and hypota urine show high fast and slow TRAPs, respectively. However, because of thei r low concentration in seminal plasma, their contribution to the TRAP is ne gligible. In conclusion, seminal plasma possesses a high antioxidant buffer capacity that protects spermatozoa from oxidative stress. Moreover, these findings suggest that the fast and slow TRAPs may have an important role as infertility markers and treatment targets in future antioxidant therapies.