Occurrence of UVA- and UVB-absorbing compounds in 152 species (206 strains) of marine microalgae

Abstract

Marine microalgae (152 species, 206 strains) from 12 classes were examined for the presence of UVA- and UVB-absorbing compounds. Cultures were grown under white fluorescent light without supplementary UVA or UVB radiation and were extracted after harvest in tetrahydrofuran:methanol (20:80, v/v). Ratios of UV absorbance (280 to 390 nm) to chlorophyll a (chl a) (665 nm) obtained by spectrophotometry ranged from 0.18 to 6.75. Three groups of species were distinguished: those with low UV:chl a ratios (0.18 to 0.9, diatoms, green algae, cyanophytes, euglenophytes, eustigmatophytes, rhodophytes, some dinoflagellates, some prymnesiophytes), those with intermediate ratios (0.9 to 1.4, chrysophytes, some prasinophytes, some prymnesiophytes) and those with very high ratios (1.4 to 6.75, surface bloom-forming dinoflagellates, cryptomonads, prymnesiophytes and raphidophytes). UV-absorbing pigments varied across species of the same algal class and strains of the same species. HPLC analysis of extracts of 5 species (1 diatom, 2 bloom-forming raphidophytes and 2 bloom-forming dinoflagellates) showed suites of mycosporine-like amino acids in 4 of them, which included mycosporine-glycine, asterina-330, shinorine, porphyra-334 and palythine. The dinoflagellate Gymnodinium catenatum also contained major quantities of unknown UV-absorbing compounds.