Metabolically-active human mitochondria were impregnated with a site-specific, chemiluminescent probe and different mixtures of known or suspected antioxidants and/or geroprotectors. Superoxide flux from the endomitochondrial respiratory chain and from exomitochondrial sources were measured in regard to the degree of protection from different geroprotective mixtures. In human mitochondria, mixtures of choline, RNA, ACF 223, BHT, copper, alpha-tocopherol, ascorbic acid and mercaptans showed some indication of superoxide scavenger effect, especially when compared to hydroxy-group substances such as mannitol, glucose and ethanol. Both in rat and human mitochondria, strong synergetic effects were evidenced by formulations incorporating alpha-tocopherol, BHT, ACF 223 and mercaptoamino acids.