(3S,3'S,5R,5'R, 6S,6'S)-5,6:5',6'-Diepoxy-5,5',6,6'-tetrahydro-beta,beta-carotene-3,3'-diol 126-29-4 5,6:5',6'-Diepoxy-5,5',6,6'-tetrahydro-beta-carotene-3,3'-diol Violaxanthin Zeaxanthin diepoxide