Characteristic oxidation behavior of β-cyclocitral from the cyanobacterium Microcystis
- 416 Downloads
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.
Keywordsβ-cyclocitral Oxidation Acidification Cyanobacteria Blue color formation Lysis
We acknowledge Drs. Atsushi Miyachi and Andrea Roxanne J. Anas and Mr. Kohei Kawai for measurement of the high-resolution mass spectral data, NMR measurement, and technical assistance, respectively, in this study.
- Fallon RD, Brook TD (1979) Lytic organisms and photooxidative effects: influence on blue-green algae cyanobacteria in Lake Mendota. Wisconsin Appl Environ Microbiol 38(3):499–505Google Scholar
- Harada K-I, Tsuji K, Ohta A, Takayanagi K, Tamaki S, Suzuki T, Ito E, Fujii K (2007) Isolation of a lytic bacterium against cyanobacteria and its active compounds. J Res Inst Meijo Univ 6:17–28Google Scholar
- Sigee DC (2005) Freshwater microbiology: biodiversity and dynamic interactions of microorganisms in aquatic environment. John Wiley and Sons, Inc., Chichester, UKGoogle Scholar
- Watanabe MF, Harada K-I, Carmichael WW, Fujiki H (1996) Toxic microcystis. CRC Press, Boca Raton, FLGoogle Scholar