Phytochemical and enzyme inhibitory activities of Euphorbia prostrata and Convolvulus arvensis extracts against Tribolium castaneum

Background The red flour beetle, Tribolium castaneum , is a persistent stored-product pest, while resistance and residue concerns limit exclusive reliance on synthetic insecticides. Although Euphorbia prostrata and Convolvulus arvensis have been chemically profiled in previous studies, their activities have not been compared within one experimental system integrating acute toxicity, progeny suppression, enzyme inhibition, and phytochemical–bioactivity relationships. Methods Hydro-methanolic extracts were tested at 2.5–80 mg/mL. Corrected adult contact mortality was measured after 24, 48, and 72 h using two independent runs, each with four biological replicates of 20 adults per treatment. Treated-grain assays quantified F1 emergence, and four independently prepared insect homogenate pools per treatment were analyzed in technical triplicate for acetylcholinesterase (AChE), carboxylesterase, glutathione S-transferase (GST), and α-amylase inhibition. GC–MS assignments were made tentatively against the NIST 20 library. Concentration–response modeling, factorial analysis, correlation, regression with multicollinearity control, and principal component analysis were performed in R 4.5.1. Results E. prostrata had a higher extraction yield (13.84 ± 0.42%) and higher total phenolic and flavonoid contents than C. arvensis . At 80 mg/mL after 72 h, corrected contact mortality was 97.92% for E. prostrata and 94.79% for C. arvensis . The corresponding LC 50 values (95% CI) were 6.86 mg/mL (5.72–8.24) and 9.84 mg/mL (8.31–11.64), respectively. At 80 mg/mL, F1 progeny inhibition reached 97.28% and 93.83%. AChE was the most sensitive enzyme target, with IC 50 values of 12.31 mg/mL (10.42–14.51) and 17.82 mg/mL (15.10–21.01). Exploratory mean-profile analyses showed strong dose-linked associations; because only 12 extract-by-concentration profiles were available, these analyses were treated as hypothesis-generating. Conclusion Under the tested laboratory conditions, both extracts produced contact toxicity, reduced F1 emergence, and inhibited insect enzymes, with E. prostrata showing greater activity. These findings justify fractionation, residue, formulation, non-target-safety, and semi-field studies, but they do not establish field efficacy or safe use on stored food.