| Summary: | Mycosporine-like amino acids (MAAs) are widespread in various microbes and protect them against harsh environments. Here, four different <i>Aphanizomenon</i> species were isolated from severely eutrophic waterbodies, Lake Dianchi and the Guanqiao fishpond. Morphological characters and molecular phylogenetic analysis verified that the CHAB5919, 5921, and 5926 strains belonged to the <i>Aphanizomenon flos-aquae</i> clade while Guanqiao01 belonged to the <i>Aphanizomenon</i> gracile clade. Full wavelength scanning proved that there was obvious maximal absorption at 334 nm through purified methanol extraction, and these substances were further analyzed by HPLC and UPLC-MS-MS. The results showed that two kinds of MAAs were discovered in the cultured <i>Aphanizomenon</i> strains. One molecular weight was 333.28 and the other was 347.25, and the daughter fragment patterns were in accordance with the previously articles reported shinorine and porphyra-334 ion characters. The concentration of the MAAs was calibrated from semi-prepared MAAs standards from dry cells of <i>Microcystis aeruginosa</i> PCC7806 algal powder, and the purity of shinorine and porphyra-334 were 90.2% and 85.4%, respectively. The average concentrations of shinorine and porphyra-334 were 0.307–0.385 µg/mg and 0.111–0.136 µg/mg in <i>Aphanizomenon flos-aquae</i> species, respectively. And there was only one kind of MAAs (shinorine) in <i>Aphanizomenon gracile</i> species.,with a content of 0.003–0.049 µg/mg dry weight among all <i>Aphanizomenon gracile</i> strains. The shinorine concentration in <i>Aphanizomenon flos-aquae</i> was higher than that in <i>Aphanizomenon gracile</i> strains. The total MAAs production can be ranked as <i>Aphanizomenon flos-aquae</i> > <i>Aphanizomenon gracile</i>.
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