Biotransformation of fucoxanthinol into amarouciaxanthin A in mice and HepG2 cells: formation and cytotoxicity of fucoxanthin metabolites.

Abstract

Fucoxanthin, a major carotenoid in edible brown algae, potentially inhibits the proliferation of human prostate cancer cells via apoptosis induction. However, it has been postulated that dietary fucoxanthin is hydrolyzed into fucoxanthinol in the gastrointestinal tract before absorption in the intestine. In the present study, we investigated the further biotransformation of orally administered fucoxanthin and estimated the cytotoxicity of fucoxanthin metabolites on PC-3 human prostate cancer cells. After the oral administration of fucoxanthin in mice, two metabolites, fucoxanthinol and an unknown metabolite, were found in the plasma and liver. The unknown metabolite was isolated from the incubation mixture of fucoxanthinol and mouse liver preparation (10,000 g supernatant of homogenates), and a series of instrumental analyses identified it as amarouciaxanthin A [(3S,5R,6'S)-3,5,6'-trihydroxy-6,7-didehydro-5,6,7',8'-tetrahydro-beta,epsilon-carotene-3',8'-dione]. The conversion of fucoxanthinol into amarouciaxanthin A was predominantly shown in liver microsomes. This dehydrogenation/isomerization of the 5,6-epoxy-3-hydroxy-5,6-dihydro-beta end group of fucoxanthinol into the 6'-hydroxy-3'-oxo-epsilon end group of amarouciaxanthin A required NAD(P)+ as a cofactor, and the optimal pH for the conversion was 9.5 to 10.0. Fucoxanthinol supplemented to culture medium via HepG2 cells was also converted into amarouciaxanthin A. The 50% inhibitory concentrations on the proliferation of PC-3 human prostate cancer cells were 3.0, 2.0, and 4.6 microM for fucoxanthin, fucoxanthinol, and amarouciaxanthin A, respectively. To our knowledge, this is the first report on the enzymatic dehydrogenation of a 3-hydroxyl end group of xanthophylls in mammals.

• Authors: Akira Asai, Tatsuya Sugawara, Hiroshi Ono, Akihiko Nagao
• Journal: Drug metabolism and disposition: the biological fate of chemicals (Drug Metab Dispos) Vol. 32 Issue 2 Pg. 205-11 (Feb 2004) ISSN: 0090-9556 [Print] United States
• PMID: 14744942 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antineoplastic Agents
• Xanthophylls
• beta Carotene
• fucoxanthin
• amarouciaxanthin A
• fucoxanthinol

Topics

• Administration, Oral
• Animals
• Antineoplastic Agents (administration & dosage, metabolism, pharmacology)
• Cell Division (drug effects)
• Cell Line, Tumor
• Humans
• In Vitro Techniques
• Male
• Mice
• Microsomes, Liver (enzymology, metabolism)
• Prostatic Neoplasms
• Xanthophylls (administration & dosage, metabolism, pharmacokinetics, pharmacology)
• beta Carotene (administration & dosage, analogs & derivatives, metabolism, pharmacology)