The molecule is a histidine derivative that is N(alpha),N(alpha),N(alpha)-trimethyl-L-histidine substituted by a selenoxo group at position 2 on the imidazole ring. A selenium-containing antioxidant found in tuna blood. It has a role as a fungal metabolite, a marine metabolite and an antioxidant. It is an amino-acid betaine and a L-histidine derivative.