Figure 1
Chemical structure of CYN: A – sulfate group, B – tricyclic guanidine moiety, C – uracil ring
Figure 2
Mass spectra of CYN decomposition products formed under alkaline conditions (pH 10) combined with boiling temperature: A – CP-2 or CP-3, B – CP-6
Figure 3
Mass spectra of CYN decomposition products formed under alkaline conditions (pH 10) during UV-B irradiation: A – CPI-1, B – CPI-2, C – CPI-4, D – CPI-5
Table 1
Products of total CYN decomposition formed under alkaline conditions (pH 10) combined with boiling temperature
| Decomposition products | Retention [min] time | [M+H]+ | Fragmentation ions | Proposed structure |
|---|---|---|---|---|
| CP-2 or CP-3 | 1.90 | 336.14 | 194.1, 176.1 |  |
| CP-6 | 3.85 | 292.01 | 212.1, 194.1, 176.1 |  |
Table 2
Products of the total CYN decomposition formed under alkaline conditions (pH 10) during UV-B irradiation
| Decomposition products | Retention [min] time | [M+H]+ | Fragmentation ions | Proposed structure |
|---|---|---|---|---|
| CPI-1 | 1.88 | 290.29 | 210.1, 192.1 |  |
| CPI-2 | 3.87 | 292.15 | 212.1, 194.1, 176.1 |  |
| CPI-4 | 4.46 | 338.34 | 196.1, 178.1, 137.1, 110.1 |  |
| CPI-5 | 4.55 | 214.13 | 196.1, 178.1, 137.1, 110.1 |  |
Table 3
Toxicity of CYN and its decomposition products assessed with Thamnotoxkit FTM and Deltatox® II tests expressed as the concentration causing death of 50% of crustacean larvae (LC50) or 50% inhibition of the bacterial bioluminescence (IC50)
| Tested substances | Toxicity tests | |
|---|---|---|
| Thamnotoxkit FTM LC50 [μg ml−1] | Deltatox® II IC50 [μg ml−1] | |
| CYN | 0.39 | < 0.2 |
| CYN decomposition products formed under boiling temperature at pH 10 | > 3 | > 3 |
| CYN decomposition products formed under UV-B irradiation at pH 10 | > 3 | > 3 |
Figure 4
Decrease in bioluminescence observed in the Deltatox® II test: A – pure CYN (aqueous solution), B – mixture of CYN decomposition products formed under alkaline conditions (pH 10) at 100°C, C – mixture of CYN decomposition products formed under alkaline conditions (pH 10) during UV-B irradiation