To investigate anti-inflammatory effects of carotenoids from Halocynthia roretzi, gene expression levels were measured for pro-inflammatory cytokines and enzymes in the murine macrophage-like cell line, RAW264.7, stimulated with lipopolysaccharide (LPS). All-trans alloxanthin, all-trans diatoxanthin, and their 9-cis isomers isolated from H. roretzi significantly suppressed expression of IL-1beta and IL-6 mRNA in cells induced by LPS without cytotoxicity. The expression level of IL-1beta mRNA in cells treated with 25 microM all-trans alloxanthin for 24 h, followed by stimulation with 0.1 microg/mL LPS for 24 h in the presence of carotenoid decreased to 33.7+/-3.0% from that of control cells stimulated with LPS alone. All-trans diatoxanthin, 9-cis alloxanthin and 9-cis diatoxanthin also decreased expression of IL-1beta mRNA to 25.1+/-2.1, 28.2+/-0.9 and 32.9+/-3.3%, respectively, from that of control cells stimulated with LPS. IL-1beta production in culture medium was also suppressed by all-trans alloxanthin and all-trans diatoxanthin. Furthermore, all-trans alloxanthin, all-trans diatoxanthin and their 9-cis isomers suppressed the over-expression of cyclooxygenase-2 and nitric oxide synthase mRNA in RAW264.7 cells induced by LPS. The suppressive effects of these carotenoids were remarkable compared to those of beta-carotene and zeaxanthin.