Comparative functional evaluation of the atypically modified GlcHMS326 and porphyra-334, Two structurally distinct mycosporine-like amino acids

Mycosporine-like amino acids (MAAs) are natural compounds widely studied for their photoprotective and antioxidant properties. Typical MAAs consist of one or two amino acids attached to a cyclohexenone or cyclohexenimine ring, whereas atypical MAAs possess unique chemical modifications such as glycosylation and methylation. Recently, we identified an atypical MAA, GlcHMS326, from the cyanobacterium Gloeocapsa sp. BRSZ, characterized by glycosylation, methylation, and hydroxylation. In this study, we compared the chemical stability and biological activities of GlcHMS326 with those of a typical di-substituted MAA, porphyra-334. GlcHMS326 was less stable under high-temperature conditions but showed a slightly higher residual rate than porphyra-334 under the present visible-light exposure conditions. Functionally, GlcHMS326 showed stronger antioxidant and collagenase inhibitory activities but weaker antiglycative activity. Neither compound inhibited hyaluronidase activity. Both MAAs inhibited angiotensin-converting enzyme, with porphyra-334 showing stronger inhibition. These results provide insights into how chemical modifications influence the functional properties of MAAs.