The acute toxicity analysis revealed that among the obtained quinine-based QASs, compounds with cations containing either a short (1Br, 1Asp, 1Ala, 4Br, 4Asp, 4Ala) or a medium-length (2Br, 2Asp, 2Ala) substituent were characterized by EC50 values against D. magna in the range of 10-100 mg dm -3 ("slightly toxic", Fig. ). The harmful effect of the listed salts is presumably due to the aquatic toxicity of quinine, since the EC50 range estimated for the reference compound (quinine hydrochloride) is identical. As with the toxicity analyses conducted for C.