SOMMARUGA, RUBEN* and BARBARA TARTAROTTI. University of Innsbruck, Institute of Zoology and Limnology. Technikerstr. 25, 6020 Innsbruck, Austria. - A note of caution on using absolute methanol concentrations and low temperatures to quantify mycosporine-like amino acids in algae.
Mycosporine-like amino acids (MAAs), a family of UV-absorbing
compounds, are widespread among many marine and freshwater organisms,
however, no standard method to analyze these compounds is available.
Consequently, protocols to extract MAAs largely differ, for example,
in the type of solvent, concentrations, temperatures, and times used.
In this study, we tested whether the concentrations of MAAs are
affected by extraction at different temperatures and methanol (MeOH)
concentrations. Natural assemblages of freshwater phytoplankton and
the marine alga Porphyra sp. were used as test organisms. The
MAAs shinorine, palythine, MAA 331, asterina-330, and porphyra-334
present in the organisms examined were generally best extracted at
45°C in 25% aqueous MeOH. In Porphyra sp. and natural
freshwater phytoplankton, the mean total MAA concentrations obtained
with this protocol were respectively ca.13 and 3 times higher than
when extracted in 100% MeOH at 4°C. Depending on the organism
examined, both MeOH concentration and temperature affected extraction
efficiency and final MAA concentration. Our results stress the need
for a priori testing the influence of these variables to assure that
the highest concentration is obtained without altering the qualitative
MAA composition. Based on these results, direct comparison of MAA
concentrations reported in the scientific literature should be done
Key words: extraction efficiency, HPLC, lakes, phytoplankton, Porphyra