(S)-Trolox, an analogue of vitamin E, substitutes the phytyl chain with a carboxyl group. This compound serves as a model substance in structural studies and as a standard for assessing antioxidant activity. Moreover, (S)-Trolox exhibits potent and specific neuroprotective and antioxidant properties.
Menaquinone 9 (MK-9) is a vitamin K2 analog that has been found in various bacteria, including E. coli. MK-9 is UV-sensitive and binds to soluble nitrate reductase, a component of the bacterial electron transport chain. In vivo, MK-9 increases plasma prothrombin concentration in vitamin K-deficient rats.