Gram-positive bacteria
Reactive oxygen species (ROS)

The inhibition of bacterial growth by Rifamycin SV is due to the production of active species of oxygen resulting from the oxidation-reduction cycle of Rifamycin SV in the cells. The aerobic oxidation of Rifamycin SV to Rifamycin S is induced by metal ions, such as Mn ²⁺ , Cu ²⁺ , and Co ²⁺ . The most effective metal ion is Mn ²⁺ .

Rat liver sub-mitochondrial particles also generated hydroxyl radical in the presence of NADH and Rifamycin S. NADH dehydrogenase (complex I) as the major component involved in the reduction of Rifamycin S. Compared to NADPH, NADH is almost as effective (Rifamycin S) in catalyzing the interactions of these antibiotics with rat liver microsomes. Rifamycin S is shown to be readily reduced to Rifamycin SV, the corresponding hydroquinone by Fe(II). Rifamycin S forms a detectable Fe(II)-(Rifamycin S)3 complex. The Fe:ATP induced lipid peroxidation is completely inhibited by Rifamycin S. Rifamycin S can interact with rat liver microsomes to undergo redox-cycling, with the subsequent production of hydroxyl radicals when iron complexes are present.