Compositions comprising apple, grape, green tea, and olive extracts are presented herein. This synergistic formulations apple, grape, green tea, and olive extract are in amounts that provide a greater antioxidant activity or protein kinase modulating activity than provided by an equivalent amount of any one extract or a sum of the extracts. Further presented are methods of regulating oxidative stress, disease-associated protein kinase activity, and enhancing the therapeutic effect of a primary therapeutic agent. Also presented are methods of making an activity enhancing composition for regulating oxidative stress, disease-associated protein kinase activity, and enhancing the therapeutic effect of a primary therapeutic agent.