The present study was designed to investigate the phenolic contents in green tea, to evaluate the antioxidant activity of plant extract and to studying the potential effect of green tea extract to increase protective effect against oxidative stress, and study the effect of plant on chemical properties of oil used in cupcakes.  The main component of such green tea was methyle gallate, the extracts under study was found to have antioxidant activity in vitro and in vivo, green tea methanol extract recorded 0.645 at concentration of 100µg/ml in reducing power assay. In DPPH assay green tea methanol extract recorded inhibition percent of 90.4% at concentration of 100 µg/ml comparing with ascorbic acid 97.7%. Green tea have biological effect on liver functions (ALT and AST activity, ALB and TP levels), kidney functions (urea and creatinine levels) and antioxidant markers (CAT activity and MDA level). The treatment with green tea extracts led to reduction in ALT and AST activity, and an increase in total protein and albumin levels accompanied by reduction in creatinine and urea levels, meanwhile treatment with H₂O₂ caused an elevation in CAT activity and MDA level but treatment with green tea extracts affected this elevation, also green tea effected on food technology during storage period of cupcakes and effected on the acid value and peroxide value of cupcakes oil under study.