While RPM cannot be recommended as the only source of daily antioxidant protection, the compounds Icariin, Naringin, and Grape Seed Extract, all found in RPM, have been shown to possess significant antioxidant properties.
Icariin, an epimedium flavonoid and testosteron mimetic, has been shown to protect the endothelial (inner wall of the arteries) cells from hydogen-perioxide-induced damage. Furthermore, icariin appears to inhibit the expression of the enzyme, caspase-3, that promotes hydrogen-peroxide-induced cell apoptosis (cell death).
Icariin also protects linoleic acid against peroxidation of micellar cells caused by free radicals, and helps to improve memory and cognitive damage caused by aluminum poisoning.
Naringin, a flavonone of grapefruit, has been shown to have considerable anti-oxidant/DNA-protection, anti-inflammatory, blood-lipid, cholesterol-lowering, and metal-chelating properties.
Naturally-occurring and highly bioavailable, Oligomeric proanthocyanidins (OPCs) are known to possess significant anti-oxidant activity compared to vitamin c, vitamin e, and beta carotene, especially in terms of free-radical-induced lipid peroxidation and DNA damage, cytotoxicity toward cancer cells, tobacco-induced oxidative damage, liver damage due to acetominophen activity, and so on.
So, whether you take RPM daily or on workout days only, you would obtain dose-dependent anti-oxidant protection from RPM supplementation.