AP39 is a compound used to increase the levels of hydrogen sulfide (HS) within mitochondria. It consists of a mitochondria-targeting motif (triphenylphosphonium) coupled to an HS-donating moiety (dithiolethione) by an aliphatic linker. AP219 is a control compound for AP39, containing the triphenylphosphonium scaffold but lacking the HS-releasing portion.