Mycosporine-like amino acids in the marine red alga Gracilaria cornea — effects of UV and heat

Ultraviolet (UV)-absorbing mycosporine-like amino acids (MAAs) were separated from a marine red alga Gracilaria cornea using HPLC. The isolated MAAs were identified as porphyra-334 and/or shinorine by comparing them with various standards. No in vivo induction of MAAs was detected in G. cornea even when the organism was grown for 4–5 days either in the presence of UV-A and UV-B only or in combination with photosynthetically active radiation. In vitro absorption properties of MAAs were unaffected when irradiated with UV-B or subjected to heat treatment (7592°C) for up to 6 h. In comparison to MAAs, other pigments such as chlorophyll a (436 and 665 nm), carotenoids (475 nm) and phycocyanin (618 nm) were severely affected by UV-B irradiation. The results indicate a highly stable nature of MAAs against the environmental stress factors like UV-B and heat. The SDS-PAGE protein profile of G. cornea showed a gradual decrease in the intensity of protein bands at 20 kDa (a and b subunits of phycocyanin) but at the same time a gradual increase in the intensity of protein bands at 26 kDa (phycoerythrin), showing the phenomenon of chromatic adaptation (changes in pigmentation in photosynthetic organisms in response to light quality), when the organism was grown in the presence of UV plus PAR. © 2000 Elsevier Science B.V. All rights reserved.