Effects of (-)-Epigallocatechin Gallate on the Motility and Penetrability of Frozen-Thawed Boar Spermatozoa Incubated in the Fertilization Medium

Epigallocatechin gallate (EGCG) is the major polyphenol in green tea (Camellia sinensis) and is known for its antioxidant effects. The objective of the present study was to examine the effects of EGCG during in vitro fertilization (IVF) on the sperm quality and penetrability into oocytes. In the first experiment, the effects of concentration and incubation period of EGCG on the motility and penetrability of spermatozoa were examined. When frozenthawed spermatozoa were incubated in IVF medium supplemented with 0 (control), 1, 50 and 100 mu M EGCG for 1, 3 and 5 h, supplementation with 50 and 100 mu M EGCG improved motility of the spermatozoa (p < 0.05), but not viability, as compared with the control group. When frozenthawed spermatozoa were co-incubated with in vitro-matured (IVM) oocytes in IVF medium supplemented with 50 and 100 mu M EGCG for 5 h, supplementation of EGCG had positive effects on sperm penetration rates. In the second experiment, the effects of supplementation of EGCG in IVF medium on penetrability of sperm from different boars and development of fertilized oocytes were evaluated. When frozenthawed spermatozoa from six boars were co-incubated with IVM oocytes in IVF medium supplemented with 50 mu M EGCG, the effect of EGCG on sperm penetration and development of oocytes after fertilization was found to vary with individual boar. Our results indicate that motility and penetrability of boar spermatozoa are improved by co-incubation with 50 mu M EGCG, but the effects vary with individual boars.