Variability of insecticidal activity of Cupressus sempervirens L., Juniperus phoenicea L., Mentha rotundifolia (L.) Huds, and Asphodelus microcarpus Salzm. & Viv. extracts according to solvents and extraction systems

Abstract

Medicinal plants represent an enormous potential source of chemical derivatives with many therapeutic properties whose variability is modified by exogenous factors. The present research focused on the evaluation of the effects of solvents with different polarities (hydro-methanolic, hydro-ethanolic, hydro-acetonic, and aqueous) and the extraction methods: maceration extraction (ME), and ultrasound-assisted extraction (UAE) on the total phenolic content (TPC), total flavonoid content (TFC), and total condensed tannins (TCT) in Cupressus sempervirens L., Juniperus phoenicea L., Mentha rotundifolia (L.) Huds, and Asphodelus microcarpus Salzm. & Viv. extracts. The toxicity by contact of the plant extracts obtained against Tribolium castaneum (Herbst) adults was studied. The quantitative characterization revealed significant differences (p ˂0.05) in the secondary metabolites of the different extracts analyzed depending on the method and solvent used. The result of the contact test indicated that the hydro-acetonic extracts obtained by ultrasound-assisted extraction exhibited the strongest insecticidal power with a corrected mortality of 59.25 ± 6.41% and 51.72 ± 11.54% for C. sempervirens L. and J. phoenicea L., respectively, and a mortality rate of 66.66 ± 5.77% was recorded for the hydro-methanolic extract of M. rotundifolia (L.) Huds. While in A. microcarpus Salzm. & Viv., the highest mortality rate (33.33 ± 7.07%) was registered in the hydro-acetonic extract obtained by maceration. The results show that there is a strong relationship between the efficacy of extracts as biopesticides and their abundance in biomolecules.