title: Characteristic oxidation behavior of β-cyclocitral from the cyanobacterium Microcystis.
abstract: The cyanobacterium Microcystis produces volatile organic compounds such as β-cyclocitral and 3-methyl-1-butanol. The lysis of cyanobacteria involving the blue color formation has been occasionally observed in a natural environment. In this study, we focused on the oxidation behavior of β-cyclocitral that contributed to the blue color formation in a natural environment and compared β-cyclocitral with a structurally related compound concerning its oxidation, acidification, and lytic behavior. The oxidation products of β-cyclocitral were identified by the addition of β-cyclocitral in water, in which 2,2,6-trimethylcyclohex-1-ene-1-yl formate and 2,2,6-trimethylcyclohexanone were structurally characterized. That is, β-cyclocitral was easily oxidized to produce the corresponding carboxylic acid and the enol ester in water without an oxidizing reagent, suggesting that this oxidation proceeded according to the Baeyer-Villiger oxidation. The oxidation behavior of β-cyclocitral in a laboratory was different from that in the natural environment, in which 2,2,6- trimethylcyclohexanone was detected at the highest amount in the natural environment, whereas the highest amount in the laboratory was β-cyclocitric acid. A comparison of β-cyclocitral with structurally similar aldehydes concerning the lytic behavior of a Microcystis strain and the acidification process indicated that only β-cyclocitral was easily oxidized. Furthermore, it was found that a blue color formation occurred between pH 5.5 and 6.5, suggesting that chlorophyll a and β-carotene are unstable and decomposed, whereas phycocyanin was stable to some extent in this range. The obtained results of the characteristic oxidation behavior of β-cyclocitral would contribute to a better understanding of the cyanobacterial life cycle.
authors.affiliation: Aichi Prefectural Institute of Public Health, Tsujimachi, Kita, Nagoya, 462-8576, Japan. kouji_tomita@pref.aichi.lg.jp.|Graduate School of Environmental and Human Science and Faculty of Pharmacy, Meijo University, 150 Yagotoyama Tempaku, Nagoya, 468-8503, Japan. kouji_tomita@pref.aichi.lg.jp.
authors.forename: Koji
authors.initials: K
authors.lastname: Tomita
authors.affiliation: Graduate School of Environmental and Human Science and Faculty of Pharmacy, Meijo University, 150 Yagotoyama Tempaku, Nagoya, 468-8503, Japan.
authors.forename: Masateru
authors.initials: M
authors.lastname: Hasegawa
authors.affiliation: Graduate School of Environmental and Human Science and Faculty of Pharmacy, Meijo University, 150 Yagotoyama Tempaku, Nagoya, 468-8503, Japan.
authors.forename: Suzue
authors.initials: S
authors.lastname: Arii
authors.affiliation: Kanagawa Prefectural Institute of Public Health, Shimomachiya, Chigasaki, Kanagawa, 253-0087, Japan.
authors.forename: Kiyomi
authors.initials: K
authors.lastname: Tsuji
authors.affiliation: Graduate School of Environmental and Human Science and Faculty of Pharmacy, Meijo University, 150 Yagotoyama Tempaku, Nagoya, 468-8503, Japan.|Department of Plant Physiology and Development, Jagiellonian University, Gronostajowa 7, 30-387, Krakow, Poland.
authors.forename: Beata
authors.initials: B
authors.lastname: Bober
authors.affiliation: Graduate School of Environmental and Human Science and Faculty of Pharmacy, Meijo University, 150 Yagotoyama Tempaku, Nagoya, 468-8503, Japan.
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Harada
mesh_terms: D000447:Aldehydes / Q000737:chemistry* / Q000378:metabolism; D002734:Chlorophyll / Q000737:chemistry; D000077194:Chlorophyll A; D003116:Color; D004224:Diterpenes / Q000737:chemistry* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D046931:Microcystis / Q000378:metabolism*; D010084:Oxidation-Reduction; D000439:Pentanols / Q000737:chemistry* / Q000378:metabolism; D019207:beta Carotene / Q000737:chemistry
chemical_list: D000447:Aldehydes; D004224:Diterpenes; D000439:Pentanols; D019207:beta Carotene; D002734:Chlorophyll; C516118:beta-cyclocitral; C029683:isopentyl alcohol; D000077194:Chlorophyll A
keywords: Acidification; Blue color formation; Cyanobacteria; Lysis; Oxidation; β-cyclocitral