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Abstract

Background: Stored-grain pests like Tribolium castaneum pose a risk to cereal storage, and using synthetic insecticides for this purpose is associated with concerns of resistance and residues. The extracts of weeds could be used as alternative sources of bioactive compounds, but their insecticidal and enzyme-inhibitory activities have not been well documented. Methods: Hydro-methanolic extracts of Euphorbia prostrata and Convolvulus arvensis were evaluated against adult Tribolium castaneum. Extraction yield, total phenolic and flavonoid contents, class-level phytochemical abundance, and GC–MS-based constituent profiles were determined. Adult mortality was assessed after 24, 48, and 72 h, and LC50 and LC90 values were estimated using probit analysis. F1 progeny emergence, progeny inhibition, and enzyme-inhibitory activity against acetylcholinesterase, carboxylesterase, glutathione S-transferase, and α-amylase were also evaluated. Correlation, multivariable regression, and principal component analyses were used to relate phytochemical variables to bioactivity endpoints. Result: E. prostrata gave the highest yield of extraction as compared to C. arvensis (13.84 ± 0.42%) and has more total phenolic and flavonoid content. Concentration and exposure time of both extracts showed an increase in corrected adult mortality, with 97.92% and 94.79% after 72 h at 80 mg/mL for E. prostrata and C. arvensis, respectively. The LC50 values of the 72-hour exposure period were 6.86 mg/mL for E. prostrata and 9.84 mg/mL for C. arvensis. The progeny inhibition was 97.21% and 93.77% at 80mg/mL for F1 progeny. The IC50 values for E. prostrata were also found to be lower for all the enzymes tested, with the most sensitive target being the AChE enzyme. Overall, there was a strong correlation between total flavonoids and phenolic exposure, and the three outcomes of mortality, progeny inhibition, and mean enzyme inhibition. Conclusion: Euphorbia prostrata and Convolvulus arvensis extracts exhibited insecticidal, progeny-suppressive, and enzyme-inhibitory activities against Tribolium castaneum, with E. prostrata showing stronger overall bioactivity. These findings support further investigation of weed-derived extracts as potential components of stored-grain pest management strategies.

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