Isoeugenol

In this study, we compiled three categories of odorants with spicy aromas: anise class, clove class, and cinnamon class. We aimed to use molecular dynamics simulation techniques to uncover potential regularities in the activation mechanisms of the same odorant across different olfactory receptors, or vice versa, the activation mechanisms of different odorants on the same olfactory receptor. Here, molecular dynamics simulation results reveal that anisaldehyde and estragole preferentially bind to TYR residues, thereby activating the corresponding olfactory receptors. Both eugenol and isoeugenol activate OR5D18 at similar binding sites, but ultimately lead to differential conformational changes in the olfactory receptor. Additionally, the binding conformations of eugenol and methyl eugenol are nearly identical, whereas cinnamaldehyde and cinnamyl alcohol, methyl cinnamaldehyde, exhibit distinct binding conformations with the olfactory receptor. These results underscore how subtle structural changes can impact the binding mechanism of odorants.

This study investigated the stereoselective antimicrobial, anti-quorum sensing, and toxicity profiles of the enantiomers of α- and β-pinene, individually and in 1:1 combinations with 14 essential oil compounds. Minimum inhibitory concentration (MIC) assays revealed comparable activity between the α- and β-pinene enantiomers (0.25-4.00 mg/mL) when tested independently, but notable enantioselective differences in combination. S-(-)-α-pinene showed greater synergistic interactions with β-caryophyllene, estragole, and ocimene against Staphylococcus aureus (ΣFIC = 0.50), whereas R-(+)-β-pinene was synergistic with isoeugenol against Cryptococcus neoformans (ΣFIC = 0.50). Anti-quorum sensing assays using Chromobacterium violaceum demonstrated stronger inhibition by R-(+)-α-pinene (MQSIC = 0.38 ± 0.18 mg/mL; 67.02 % violacein inhibition at 0.50 mg/mL) and R-(+)-β-pinene (MQSIC = 0.50 mg/mL; 57.32 %) compared with their S-(-) counterparts (> 0.50 mg/mL; 30.72 % and 22.78 %, respectively). The most pronounced stereochemical variation was observed in combinations with γ-terpinene and ocimene (> 20 % difference in violacein inhibition). Brine shrimp lethality assays showed both α-pinene enantiomers to be non-toxic, while S-(-)-β-pinene exhibited greater toxicity (90.82 % mortality) than R-(+)-β-pinene (30.75 %) after 48 h. These findings highlight the important role of stereochemistry in determining the bio-activity and safety of α- and β-pinene, highlighting the therapeutic importance of chirality in the research of essential oil compounds.