Occurrence of mycosporine-like amino acids in the red-tide dinoflagellate Alexandrium excavatum: UV-photoprotective compounds?

Abstract

Water extracts of the red-tide dinoflagellate Alexandrium excavatum grown at 'high' light intensity (200 μE m-2 s-1) show a broad absorbance maximum in the UV region of the spectrum (310-360 nm). Using TLC and reverse-phase HPLC a series of mycosporine-like amino acids have been characterized: mycosporine-glycine (λmax = 310 nm), palythine (λmax = 320 nm), asterina-330 (λmax = 330 nm), shinorine (λmax = 334 nm), porphyra-334 (λmax= 334 nm), palythenic acid (λmax = 337 nm) and the isomeric mixture of usujirene and palythene (λmax = 359 nm). From the observed spectral changes during transference from 'low' (20 μE m-2 s-1) to 'high' (200 μE m-2 s-1) light intensities and vice versa, the series of compounds are supposed to be biogenically related to one another. The presence of these compounds in A.excavatum is discussed in relation to their possible role in the photoprotection to deleterious UV radiation. © 1990 Oxford University Press.