The Repellent Capacity against Sitophilus zeamais (Coleoptera: Curculionidae) and In Vitro Inhibition of the Acetylcholinesterase Enzyme of 11 Essential Oils from Six Plants of the Caribbean Region of Colombia.

The repellent capacity against Sitophilus zeamais and the in vitro inhibition on AChE of 11 essential oils, isolated from six plants of the northern region of Colombia, were assessed using a modified tunnel-type device and the Ellman colorimetric method, respectively. The results were as follows: (i) the degree of repellency (DR) of the EOs against S. zeamais was 20-68% (2 h) and 28-74% (4 h); (ii) the IC 50 values on AChE were 5-36 µg/mL; likewise, the %inh. on AChE (1 µg/cm 3 per EO) did not show any effect in 91% of the EO tested; (iii) six EOs ( Bursera graveolens -bark, B. graveolens -leaves, B. simaruba -bark, Peperomia pellucida -leaves, Piper holtonii (1b*)-leaves, and P. reticulatum -leaves) exhibited a DR (53-74%) ≥ C + (chlorpyrifos-61%), while all EOs were less active (8-60-fold) on AChE compared to chlorpyrifos (IC 50 of 0.59 µg/mL). Based on the ANOVA/linear regression and multivariate analysis of data, some differences/similarities could be established, as well as identifying the most active EOs (five: B. simaruba -bark, Pep. Pellucida -leaves, P. holtonii (1b*)-leaves, B. graveolens -bark, and B. graveolens -leaves). Finally, these EOs were constituted by spathulenol (24%)/β-selinene (18%)/caryophyllene oxide (10%)- B. simaruba ; carotol (44%)/dillapiole (21%)- Pep. pellucida ; dillapiole (81% confirmed by 1 H-/ 13 C-NMR)- P. holtonii ; mint furanone derivative (14%)/mint furanone (14%)- B. graveolens -bark; limonene (17%)/carvone (10%)- B. graveolens -leaves.