Development and validation of a rapid LC-MS/MS method for the quantification of mycosporines and mycosporine-like amino acids (MAAs) from cyanobacteria

Abstract

Mycosporines and mycosporine-like amino acids are ultra-violet radiation absorbing compounds produced by lichens, fungi, algae and cyanobacterial species, especially upon exposure to solar ultraviolet radiation. These compounds are photoprotective and some have additional antioxidant functions. Thus, mycosporine-like amino acids may be used as an active ingredient in cosmetic products. Analysis is generally achieved by separation using reverse-phase chromatography and, detection and quantification based upon characteristic absorption spectra and extremely high molar extinction coefficients. Herein, a validated liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) quantification method for mycosporine-like amino acids is presented. Additionally, an easy-to-handle and rapid extraction procedure was developed, which uses only water and volatile additives as the extractor solvents. The LC-MS/MS method was performed with an electrospray ionization source in positive mode using multiple reaction monitoring with a reverse-phase column. The method enabled the accurate determination and quantification of the mycosporine-like amino acids porphyra-334, shinorine and mycosporine-glycine-alanine in a 6 min running time, with detection limits of 0.002 μg mg−1, 0.001 μgmg−1 and 0.005 μg mg−1, respectively. These methods provided a simple extraction and rapid analysis procedure that efficiently identified and quantified these three mycosporine-like amino acids produced by a collection of 29 cyanobacteria. Although more mycosporine-like amino acids have also been identified, the validated method was developed focusing on the most abundant mycosporine-like amino acids produced by the investigated cyanobacteria. Mycosporine-like amino acids could be detected at levels well above the limits of detection for the LC-MS/MS method in 12 strains, irrespective of whether the cultures had been exposed to ultra-violet radiation. High levels of constitutive expression of mycosporine-like amino acids in cyanobacteria has rarely been reported and provides an opportunity to study mechanisms that regulate ultra-violet radiation induced mycosporine-like amino acids biosynthesis in the future.