With the exception of 4Asp, all quinine-based QASs showed very good (T > 150) antifeedant properties toward confused flour beetle larvae regardless of the type of substituent in the cation or anion structure (Fig. ). This is most likely due to the very strong effect of quinine structure on inhibiting the feeding of this speciesthe T value determined for quinine free base in confused flour beetle tests was equal to 189. Thus, it can be concluded that the activity of quinine against T. confusum larvae is comparable to that of azadirachtin (T = 192, see Fig. ), a substance known for its very potent biopesticidal properties. Although quinine is characterized by potent antifeedant activity toward some mosquito species , its activity toward stored product pests is reported to be significantly lower compared to azadirachtin or neem oil formulations . This is also true in the case of most of the obtained quinine-based QASs, which did not reach the effectiveness of pure azadirachtin (T = 194) to khapra beetles, and only 2Ala (T = 169) exhibited similar antifeedant activity toward larvae of this species. In the case of adult granary weevils, the differences were even more pronounced and pure azadirachtin (T = 190) was noticeably a superior feeding deterrent than any of the quinine-based compounds tested. However, the very good antifeedant activity of quinine (in the form of the free base and hydrochloride) toward T. confusum larvae, that also determines high efficacy of the majority of quinine-based QASs, is a surprising result and indicates the legitimacy of further research into the use of this alkaloid and its derivatives in the protection of plants and seeds against pests. It should also be emphasized that despite the exceptional biopesticidal activity of azadirachtin to a broad spectrum of stored product pests, this substance cannot be profitably obtained by synthetic methods due to its complex chemical structure . In addition, azadirachtin is difficult to extract in large quantities from Azadirachta indica plant matter which contributes to its high price. Therefore, the search for feeding deterrents derived from other, more readily available natural resources remains a legitimate approach. Moreover, given the high antimicrobial activity of salts 3Br, 3Asp, and 3Ala toward F. graminearum (a fungal pathogen of seeds and plants) and other microorganisms (see Fig. ), there is some potential for using the quinine-based QASs with longer alkyl substituents for comprehensive biopesticidal protection of stored grain against both pest insects and harmful plant pathogens. However, further research in this area needs to be preceded by analyses of the toxicity of the new QASs, as well as their environmental fate and effects on stored grain quality.