Detection of Cyanotoxins in Algae Dietary Supplements

Abstract

Algae dietary supplements are marketed worldwide as natural health products. Although their proprieties have been claimed as beneficial to improve overall health, there have been several previous reports of contamination by cyanotoxins. These products generally contain non-toxic cyanobacteria, but the methods of cultivation in natural waters without appropriate quality controls allow contamination by toxin producer species present in the natural environment. In this study, we investigated the presence of total microcystins, seven individual microcystins (RR, YR, LR, LA, LY, LW, LF), anatoxin-a, dihydroanatoxin-a, epoxyanatoxin-a, cylindrospermopsin, saxitoxin, and β-methylamino-l-alanine in 18 different commercially available products containing Spirulina or Aphanizomenon flos-aquae. Total microcystins analysis was accomplished using a Lemieux oxidation and a chemical derivatization using dansyl chloride was needed for the simultaneous analysis of cylindrospermopsin, saxitoxin, and β-methylamino-l-alanine. Moreover, the use of laser diode thermal desorption (LDTD) and ultra-high performance liquid chromatography (UHPLC) both coupled to high resolution mass spectrometry (HRMS) enabled high performance detection and quantitation. Out of the 18 products analyzed, 8 contained some cyanotoxins at levels exceeding the tolerable daily intake values. The presence of cyanotoxins in these algal dietary supplements reinforces the need for a better quality control as well as consumer's awareness on the potential risks associated with the consumption of these supplements.

Keywords: BMAA; LC-HRMS; LDTD; anatoxin-a; cyanobacteria; cyanotoxins; cylindrospermopsin; dietary supplements; microcystins; saxitoxin.

Figure 1

Example of peak shape from the analysis of brand #17 using LDTD-APCI-HRMS detecting (a) MMPB for total microcystins analysis, and (b) anatoxin-a (ANA-a). The analytes are represented by the integrated peaks with corresponding retention times (RT) and area (AA).

Figure 2

Example of chromatogram from the analysis of brand #15 using DNS derivatization and UHPLC-HESI-HRMS analysis for anatoxin-a (ANA-a), dihydroanatoxin-a (DH-ANA-a), epoxyanatoxin-a (E-ANA-a), and seven microcystins (RR, YR, LR, LA, LY, LY, LW, and LF). The analytes are represented by the integrated peaks with corresponding retention times (RT) and area (AA).

Figure 3

Example of chromatogram from the analysis of brand #15 using DNS derivatization and UHPLC-HESI-HRMS analysis for cylindrospermopsin (CYN), saxitoxin (STX), β-methylamino-l-alanine (BMAA), and diaminobutyric acid-D₃ (DAB-D₃). The analytes are represented by the integrated peaks with corresponding retention times (RT) and area (AA).

Figure 4

Fragmentation mass spectra of dihydroanatoxin-a (DH-ANA-a) with targeted product ions m/z 168 > 93, 133, and 150 and epoxyanatoxin-a (E-ANA-a) with targeted product ions m/z 182 > 98, 122, and 164.