title: UV radiation-induced biosynthesis, stability and antioxidant activity of mycosporine-like amino acids (MAAs) in a unicellular cyanobacterium Gloeocapsa sp. CU2556.
abstract: The biosynthesis of natural sunscreening compounds as influenced by ultraviolet radiation, their stability and antioxidant activity were studied in the cyanobacterium Gloeocapsa sp. CU-2556. An analysis by high-performance liquid chromatography (HPLC) with photodiode-array (PDA) detection revealed the biosynthesis of two MAAs, shinorine (UVλmax 333nm) and an unknown MAA designated as M-307 (UVλmax 307nm) with retention times of 5.9 and 6.4min, respectively. Induction of the synthesis of MAAs was studied under 395 (PAR), 320 (PAR+UV-A) and 295 (PAR+UV-A+UV-B) nm cut-off filters. MAAs induction was significantly increased with an increase in exposure time up to 72h in the samples covered with 295nm cut-off filters. Contrary to shinorine, the biosynthesis of M-307 was more dominant in this unicellular cyanobacterium. Both MAAs were highly stable to some physico-chemical stressors such as UV radiation, heat and a strong oxidizing agent. The MAA M-307 was more stable under strong oxidative stress than shinorine. Moreover, UV-C radiation drastically decreased the stability of both MAAs. The MAAs (shinorine+M-307) also exhibited efficient antioxidant activity which was dose-dependent. The results indicate that MAAs may perform a vital role in survival and sustainability of Gloeocapsa sp. CU-2556 in harsh environmental conditions by its ability to absorb/screen short wavelength UV radiation and antioxidant function.
authors.affiliation: Laboratory of Cyanobacterial Biotechnology, Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand. Electronic address: raj_rastogi@rediffmail.com.
authors.forename: Rajesh P
authors.initials: RP
authors.lastname: Rastogi
authors.affiliation: Laboratory of Cyanobacterial Biotechnology, Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand. Electronic address: aran.i@chula.ac.th.
authors.forename: Aran
authors.initials: A
authors.lastname: Incharoensakdi
mesh_terms: D000596:Amino Acids / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D000975:Antioxidants / Q000302:isolation & purification / Q000494:pharmacology; D000458:Cyanobacteria / Q000378:metabolism / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D000596:Amino Acids; D000975:Antioxidants
keywords: Antioxidant; Cyanobacteria; Mycosporine-like amino acid; Stability; UV radiation