Integrated evaluation of medicinal plant extracts: phytochemical composition, insecticidal activity, and biochemical impacts on the Angoumois grain moth for sustainable grain protection

Abstract

Abstract Post-harvest losses from insect pests, such as the Angoumois grain moth ( Sitotroga cerealella ), remain a major constraint on global food security, particularly in stored cereal grains. This study evaluated methanolic extracts of four medicinal plants— Lantana camara , Origanum majorana , Ocimum basilicum , and Ammi visnaga . The study assessed their phytochemical constituents, GC–MS chemical profiles, antioxidant and insecticidal activities, physiological effects on S. cerealella , and protective effects on stored grains, while exploring correlations among these properties. O. basilicum and O. majorana were richest in phenolics (2.66 and 2.10 mg GA g −1 ) and flavonoids (3.19–3.39 mg QE g −1 ), corresponding with strong antioxidant capacity (IC 50 = 75.51 and 80.83 µg mL −1 ). L. camara showed the highest acute toxicity (LC 50 = 3.31 mg g −1 ), whereas O. basilicum and O. majorana caused the strongest sublethal effects, suppressing adult emergence by > 80% at LC 25 . Grain protection assays demonstrated that O. basilicum provided the best long-term protection at LC 90 . Enzyme assays revealed that O. basilicum and O. majorana significantly enhanced antioxidant defenses (SOD, GSH), whereas A. visnaga reduced detoxification-related enzymes (ALT, ALP). Pearson correlation analyses revealed strong negative associations between phenolic content and grain weight loss (GWL) and insect-damaged grains (IDGs), as well as between antioxidant potential (DPPH-IC 50 ) and insect emergence reduction (ER). These findings demonstrate the multifunctional value of phenolic-rich extracts for sustainable botanical pest control and grain preservation, supporting their potential incorporation into sustainable post-harvest management strategies.