Characteristic oxidation behavior of [beta]-cyclocitral from the cyanobacterium Microcystis

• Published in: Environmental science and pollution research international Vol. 23; no. 12; p. 11998
• Main Authors: Tomita, Koji, Hasegawa, Masateru, Arii, Suzue, Tsuji, Kiyomi, Bober, Beata, Harada, Ken-ichi
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer Nature B.V 01-06-2016
• Subjects: Acidification; Aldehydes; Biodiesel fuels; Butanol; Carboxylic acids; Color; Cyanobacteria; Isopentyl alcohol; Laboratories; Lysis; Microcystis; Natural environment; Organic compounds; Oxidation; Public health; Sensors; Studies; VOCs; Volatile organic compounds; β-Carotene; Japan
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-016-6369-y

The cyanobacterium Microcystis produces volatile organic compounds such as [beta]-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 [beta]-cyclocitral that contributed to the blue color formation in a natural environment and compared [beta]-cyclocitral with a structurally related compound concerning its oxidation, acidification, and lytic behavior. The oxidation products of [beta]-cyclocitral were identified by the addition of [beta]-cyclocitral in water, in which 2,2,6-trimethylcyclohex-1-ene-1-yl formate and 2,2,6-trimethylcyclohexanone were structurally characterized. That is, [beta]-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 [beta]-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 [beta]-cyclocitric acid. A comparison of [beta]-cyclocitral with structurally similar aldehydes concerning the lytic behavior of a Microcystis strain and the acidification process indicated that only [beta]-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 [beta]-carotene are unstable and decomposed, whereas phycocyanin was stable to some extent in this range. The obtained results of the characteristic oxidation behavior of [beta]-cyclocitral would contribute to a better understanding of the cyanobacterial life cycle.