Evaluation of the insecticidal activity of bioactive compounds obtained from Azolla pinnata and Azolla microphylla

Plant extracts offer an alternative approach to safeguarding stored food products. Our research is focused on assessing the insecticidal properties of aqueous and ethanolic extracts containing bioactive compounds obtained from two species of Azolla; A. pinnata and A. Microphylla against pests that affect stored food items. Two drying processes were conducted in order to compare the yield of bioactive compounds (freeze-drying and oven-drying). We employed two extraction methods (maceration and decoction), using ethanol and water as solvents. Phytochemical screening of both extracts was carried out by CG-MS analysis. The insecticidal properties of the obtained extracts were assessed using the spraying method on larvae and adults of Tribolium castaneum. The results indicated that the freeze-dried method was more efficient comparing to oven-drying, recording the highest value of 26.07%, with the ethanolic extract by decoction. GC–MS analysis for both species confirmed the existence of primarily fatty acid, terpenoid, steroid, coumarin, and flavonoid derivatives compounds. Overall, the various extracts exhibited high toxicity against both larvae and adults. The mortality rate was increased according to the increasing concentration of extracts. The lowest LC₅₀ of A. pinnata and A. microphylla extracts were found to be 872.42 and 894.65 µg/mL, respectively. The aqueous extract caused higher toxicity, reaching 96%. The findings of this study suggest that the dry matter from both azolla species exhibited significant toxicity, evidenced by the mortality of both the larvae and adults. Extracts from A. pinnata were found to be more toxic to T. castaneum in comparison with A. microphylla extracts.