Methyl Isoeugenol

Methyl isoeugenol (CAS 93-16-3; isoeugenyl methyl ether) is the methyl ether of isoeugenol and has the structure 1,2-dimethoxy-4-(prop-1-enyl)benzene, whereas methyl eugenol (CAS 93-15-2) is 4-allyl-1,2-dimethoxybenzene with a terminal allyl double bond; the two are positional isomers that differ in double-bond location. Eugenol (CAS 97-53-0) and isoeugenol (CAS 97-54-1) both retain a free phenolic hydroxyl group, with allyl and propenyl side chains respectively; methylation and double-bond position alter odour, oxidation behaviour, and metabolic pathways, so methyl isoeugenol commonly gives softer clove, carnation, and floral facets, while methyl eugenol is generally more spicy and aromatic. Methyl eugenol can undergo benzylic hydroxylation and sulfation to form reactive metabolites associated with DNA-adduct risk and is classified by IARC as Group 2A, whereas isoeugenol is Group 2B; methyl isoeugenol was not separately evaluated in IARC Volume 134, which should not be interpreted as evidence of absence of hazard or as automatic substitutability (Zhang et al., 2022, Archives of Toxicology; IARC Working Group, 2024, IARC Monographs Volume 134). Methyl isoeugenol has its own FEMA 2476 and U.S. 21 CFR 172.515 identity, but food, fragrance, cosmetic, and other applications still require market-specific review; purchasing documents must state the exact name, CAS number, GC assay, and SDS to prevent substitution among 93-16-3, 93-15-2, 97-53-0, and 97-54-1.

Methyl isoeugenol can serve as a heart-to-base material in spicy and floral fragrances, contributing softer, sweeter, persistent clove, carnation, floral, and slightly smoky facets in carnation, rose, tuberose, ylang-ylang, and oriental compositions while extending dry-down. In practice, "isoeugenol regulating agent" should mean that it can be blended with isoeugenol to adjust clove-spice intensity, roundness, and substantivity and, where appropriate, reduce the level of isoeugenol required; it is not a regulatory exemption and does not remove the need for finished-formula safety and labelling assessment. Isoeugenol is restricted under entry 73 of Annex III to the EU Cosmetics Regulation: it is limited to 0.02% in finished non-oral products and requires individual labelling above 0.001% in leave-on products or 0.01% in rinse-off products, while methyl isoeugenol is not listed as a synonym or substitute under that Annex III entry (European Commission, 2009, Regulation (EC) No 1223/2009, Annex III). Under the current 51st Amendment, methyl isoeugenol has no separate IFRA category restriction identified, but the current supplier IFRA Certificate of Conformity, SDS, and finished-product safety assessment remain necessary; because it may turn red under light and in alkaline bases, it should not be used directly in high-pH shampoos, shower gels, or soap systems without accelerated-stability verification.

Methyl isoeugenol (isoeugenyl methyl ether, CAS 93-16-3) is currently listed in Appendix B.3 of GB 2760-2024 as a permitted synthetic food flavouring substance under code S0081 with FEMA number 2476; its technical requirement is not less than 95% assay, and actual use must follow the applicable principles for food flavourings and compounded food flavours. Internationally, it has JECFA number 1266, EU FLAVIS number 04.013, and a U.S. 21 CFR 172.515 identity; JECFA concluded in 2003 that it presents "no safety concern at current levels of intake" when used as a flavouring, rather than establishing a fixed ADI of 5 mg/kg body weight per day (JECFA, 2003, Safety Evaluation of Certain Food Additives and Contaminants). Methyl isoeugenol and methyl eugenol (CAS 93-15-2) are positional isomers, but they require separate toxicological and regulatory assessment: methyl eugenol is classified by IARC as Group 2A and cannot be used as a directly added food flavouring in the EU or United States, whereas methyl isoeugenol was not separately evaluated in IARC Volume 134 and retains its own food-flavouring identity (IARC Working Group, 2024, IARC Monographs Volume 134). Customers should therefore manage methyl isoeugenol using its exact CAS number, chemical name, GC assay, and target-market regulatory documentation and should not transfer the carcinogenicity classification, prohibition status, or compliance documents of methyl eugenol directly to methyl isoeugenol.