Oxidative metabolites of lycopene and γ-carotene in gac (Momordica cochinchinensis).

Three new oxidative metabolites of lycopenes, (erythro)-lycopene-5,6-diol, (threo)-lycopene-5,6-diol, and 1,16-dehydro-2,6-cyclolycopene-5-ol B, and four new oxidative metabolites of γ-carotenes, 2',6'-cyclo-γ-carotene-1',5'-diol A, 2',6'-cyclo-γ-carotene-1',5'-diol B, (erythro)-γ-carotene-5,6-diol, and (threo)-γ-carotene-5,6-diol, were isolated as minor components from the aril of gac, Momordica cochinchinensis. These structures were determined on the basis of spectroscopic data, and some of them were compared to the structures of synthetic samples. Furthermore, the oxidative metabolic conversion pathways of lycopene and γ-carotene were discussed.

Auto-oxidation products of astaxanthin.

The auto-oxidation products of astaxanthin were investigated. Astaxanthin was allowed to react with atmospheric oxygen at 55°C in the dark for 35 days. A series of oxidative cleavage products, 7-apoastaxanthinal (1), 9-apoastaxanthinone (2), 11-apoastaxanthinal (3), 13-apoastaxanthinone (4), 15-apoastaxanthinal (5), 14'-apoastaxanthinal (6), 12'-apoastaxanthinal (7), 10'-apoastaxanthinal (8), and 8'-apoastaxanthinal (9), were identified. Among them, 3 and 6 were isolated and characterized for the first time. Cleavage of the double bond in astaxanthin was discussed on the basis of the calculation of the stable molecular energy.

Structure of minor carotenoids from the crown-of-thorns starfish, Acanthaster planci.

Four new carotenoids, named 4-ketodeepoxyneoxanthin (1), 4-keto-4'-hydroxydiatoxanthin (2), 3'-epigobiusxanthin (3), and 7,8-dihydrodiadinoxanthin (4), were isolated from the crown-of-thorns starfish, Acanthaster planci. Their structures were determined on the basis of chemical and spectroscopic data.

Reaction of astaxanthin with peroxynitrite.

The in vitro reactivities of astaxanthin toward peroxynitrite were investigated and the reaction products after scavenging with peroxynitrite were analyzed in order to determine the complete mechanism of this reaction. A series of carotenoids, 13-apo-astaxanthinone (1), 12'-apo-15'-nitroastaxanthinal (2), 12'-apo-astaxanthinal (3), 10'-apo-astaxanthinal (4), 9-cis-14'-s-cis-15'-nitroastaxanthin (5), 14'-s-cis-15'-nitroastaxanthin (6), 13-cis-14'-s-cis-15'-nitroastaxanthin (7), 10'-s-cis-11'-cis-11'-nitroastaxanthin (8), 13,15,13'-tri-cis-15'-nitroastaxanthin (9), 9-cis-astaxanthin (10), and 13-cis-astaxanthin (11), were isolated from the reaction products of carotenoids with peroxynitrite. Our previous studies achieved for the first time the isolation of nitro derivatives from the reaction of astaxanthin with peroxynitrite. Here we identify the major remaining reaction products of this reaction and investigate the stabilities of the nitro astaxanthins.

Reaction of retinol with peroxynitrite.

The reactivity of retinol with peroxynitrite, which is a strong oxidant and has been reported to induce several biological damages, was investigated. 13-cis-14-nitroretinol (1), 13-trans-14-nitroretinol (2), 13-apo-beta-carotenone (3), retinal (4), 11,14-epoxyretinol (5), and 11,15-epoxyretinol (6) were identified as reaction products of retinol with peroxynitrite. From these results, it was observed that retinol can undergo a nitration reaction with peroxynitrite. Furthermore, the formation mechanisms of 1, 2, and 3 from retinol with peroxynitrite are discussed.

Two diphenylpropan-1,2-diol syringates from the roots of Erythrina variegata.

Two new diphenylpropan-1,2-diols, eryvarinols A (1) and B (2), were isolated from the roots of Erythrina variegata. Their structures were elucidated as 1-(4-hydroxy-2-methoxyphenyl)-2-(4-hydroxy-3,5-dimethoxybenzoyloxy)-3-(4-hydroxyphenyl)propan-1-ol (1) and its 3"-prenyl derivative (2) on the basis of spectroscopic and chemical evidence. Both these compounds are unusual diphenylpropan-1,2-diols with a syringyl group.