Disclosed herein are mono or di-succinate compounds where one or both of the acid groups in the succinate core are protected in the form of biologically labile moieties, and the use of said compounds to enhance mitochondrial function. The compounds may be of formula (I) wherein R1 is H or an optionally substituted alkyl group or a group of formula (II) and R2 is independently a group according to formula (II) where formula (II) is as defined 10 herein.