Methyl Eugenol

Methyl eugenol (ME) is a volatile plant phenylpropene and a highly effective plant-derived parapheromone for male oriental fruit flies (Bactrocera dorsalis) and several related dacine fruit flies; males are strongly attracted to and consume ME, whereas females do not normally show the same direct attraction (Nishida et al., 1988, Experientia; Liu et al., 2018, Frontiers in Physiology). After feeding, males can convert ME into metabolites including (E)-coniferyl alcohol and 2-allyl-4,5-dimethoxyphenol, which accumulate in the rectal gland and are released during dusk courtship, increasing the attractiveness of male leks to females and improving mating competitiveness (Zhang et al., 2024, Nature Communications). In some Bulbophyllum orchids, flowers release ME to attract male fruit flies, which transfer pollen during flower visits and form a highly specialised plant–insect pollination relationship; Bulbophyllum cheiri flowers were reported to attract more wild male oriental fruit flies than an equivalent quantity of commercial ME lure (Tan et al., 2021, Journal of Asia-Pacific Entomology). ME therefore functions in pest management by mimicking a natural floral signal to attract target males for surveillance, male annihilation, or sterile-insect programmes; its primary action is behavioural attraction, while actual insect mortality depends on trap design, associated killing components, and the wider area-wide IPM programme.

Methyl eugenol (CAS 93-15-2; 4-allyl-1,2-dimethoxybenzene) is a naturally occurring phenylpropene found in herbs, spices, and essential oils including basil, tarragon, nutmeg, clove, mace, bay, and citronella, although its actual concentration varies substantially by botanical source and chemotype (IARC, 2024, IARC Monographs Volume 134). The pure material is normally a colourless to pale-yellow liquid with a boiling point of approximately 254–255°C, melting point of approximately −4°C, density of approximately 1.036 g/mL, and refractive index 𝑛20/D of approximately 1.534; it is sparingly soluble in water and soluble in ethanol and oil phases, so the page values should be corrected to RI 1.532–1.535 and SG 1.032–1.040 rather than the currently transposed values. Eugenol (CAS 97-53-0) has a free phenolic hydroxyl group, whereas methyl eugenol has two aromatic methoxy groups; methyl isoeugenol (CAS 93-16-3) has a different double-bond position, so the three materials must never share CAS numbers, COAs, SDSs, or regulatory documentation. Methyl eugenol is classified by IARC as probably carcinogenic to humans (Group 2A), while isoeugenol is classified as Group 2B; a 99% GC result establishes chemical assay only and does not replace regulatory review and exposure assessment for food, fragrance, cosmetic, lure, or other final uses (IARC, 2024, IARC Monographs Volume 134).

In China, methyl eugenol remains listed as S0093 with FEMA number 2475 in Appendix B.3, "List of Permitted Synthetic Food Flavouring Substances," of GB 2760-2024, with a technical requirement of not less than 95% content; its use must follow the applicable principles for food flavourings and compounded food flavours and should not be interpreted as unrestricted direct addition to every food. The EU and United States prohibit methyl eugenol as a directly added food flavouring; the U.S. FDA has removed methyl eugenol and five other synthetic flavouring substances from the food-additive regulations, although naturally occurring methyl eugenol from herbs and spices such as basil, nutmeg, and clove may still enter foods (U.S. FDA, 2024, FDA Removes 7 Synthetic Flavoring Substances from Food Additives List). In 2024, IARC classified methyl eugenol as probably carcinogenic to humans, Group 2A, based on sufficient evidence of carcinogenicity in experimental animals and strong mechanistic evidence, while evidence in humans was inadequate; this is a hazard-identification conclusion, not an automatic change to Chinese GB 2760 permission or a quantitative risk determination for every low-dose exposure (IARC Working Group, 2024, IARC Monographs Volume 134). For Chinese food-flavour customers, raw-material identity, purity, and final-food use should be managed under GB 2760-2024; for EU or U.S. markets, methyl eugenol should not be positioned as a directly added food flavouring, and botanical oils containing naturally occurring methyl eugenol should be quantitatively tested and checked against target-market requirements.