Antinutritional and insecticidal potential of Chenopodium quinoa saponin rich extract against Tribolium castaneum (Herbst) and its action mechanism.

Tribolium castaneum can inflict significant harm to stored grains. The use of novel, harmless, and effective biopesticides is needful to avoid the hazardous effects of chemical insecticides. On the other hand, saponins are antinutritional metabolites with large biological properties, and quinoa husk is one of the richest biomasses in these compounds. The biocidal and antinutritional effects of a saponin-rich extract (SRE) from Chenopodium quinoa husk were examined against T. castaneum adults by evaluating mortality, nutritional indices, and mortality rate. The effect on T. castaneum's enzymatic activity was also investigated. As a result, at concentrations above 25 mg/g of SRE, insects can no longer consume flour with a significant feeding deterrent (≥ 84.20%). The study showed that SRE has an acute and long-term effect on insect survival, which confirms that the mortality of T. castaneum is attributable to the toxic action of the saponin extract and not just the starvation action. In addition, SRE demonstrated its capacity to disrupt the wax layer of T. castaneum adults, penetrate insects, and react as oxidative stressors, which explain the affectation of the immune defense system of T. castaneum through the downregulation of phenoloxidase activity and glutathione S-transferase, the upregulation of the antioxidant system presented in this study with catalase activity, and causing organelle damage in the midgut tissues confirmed by the inhibition of amylase activity. According to the findings of this study, saponin extract has a very interesting application as an insecticide against storage insects.