title: Detoxification and degradation of microcystin-LR and -RR by ozonation.
abstract: In the present study, two Microsystins (MCs) of Microcystin-LR and Microcystin-RR were degraded with different dosages of ozone (O(3)). The possible degradation pathways were elucidated by analyzing their intermediates and end-products with liquid chromatography-mass spectrometry (LC-MS) method. The toxicity of the MCs ozonation products was also evaluated by assaying the protein phosphatase inhibition in vitro and acute toxicity in vivo. Results demonstrated that ozonation was a promising technology for removal and detoxification of the cyanotoxins. The MCs destruction was mainly involved in the attack of ozone on Adda side chain. First, the conjugated diene structure of Adda moiety was attacked by hydroxyl radical (OH()) to produce dihydroxylated products, then the hydroxylated 4-5 and/or 6-7 bond of Adda was cleaved into aldehyde or ketone peptide residues, and finally the residues were oxidized into the corresponding carboxylic acids. The fragmentation of the Mdha-Ala peptide bond of MCs also contributed positively to the oxidation process. Additionally, the attack on the benzene ring of Adda side chain was exclusively observed during MC-RR degradation. The toxicity evaluation of MCs ozonation products revealed that those end-products had no adverse effects in vivo and in vitro ozonation that could completely remove the MCs' toxicity.
authors.affiliation: School of Environment and Civil Engineering, Jiangnan University, Wuxi 214122, China. hfmiao@yahoo.com.cn
authors.forename: Heng-Feng
authors.initials: HF
authors.lastname: Miao
authors.forename: Fang
authors.initials: F
authors.lastname: Qin
authors.forename: Guan-Jun
authors.initials: GJ
authors.lastname: Tao
authors.forename: Weny-Yi
authors.initials: WY
authors.lastname: Tao
authors.forename: Wen-Quan
authors.initials: WQ
authors.lastname: Ruan
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid; D017665:Hydroxyl Radical / Q000378:metabolism; D008297:Male; D008387:Marine Toxins; D051379:Mice; D052998:Microcystins / Q000737:chemistry* / Q000633:toxicity; D010084:Oxidation-Reduction; D010126:Ozone / Q000737:chemistry*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization; D014873:Water Pollutants / Q000737:chemistry* / Q000633:toxicity
chemical_list: D008387:Marine Toxins; D052998:Microcystins; D014873:Water Pollutants; D017665:Hydroxyl Radical; D010126:Ozone; C063855:microcystin RR; D010749:Phosphoprotein Phosphatases; C057862:cyanoginosin LR