eugenol

Eugenol is the reason a cook can swap allspice for clove and get most of the same effect. Clove bud oil runs 68 to 82 percent eugenol; allspice berry oil, compiled across growing regions, runs 64 to 86 percent, from Guatemala's 65.9 to Jamaica's 86.4. A flower bud from the Moluccas and a berry from the Caribbean, on opposite sides of the world, both build their oil around the same molecule, and because both plants are Myrtaceae the convergence is not entirely random. In this library it arrives by both routes: cloves season two spice blends, allspice seasons a savory dish and a third blend, four recipes across two kitchens.

Eugenol, C₁₀H₁₂O₂, is a phenol, and the famous percentages are easy to misread: cloves are usually quoted at eighty-five to ninety percent eugenol, but that is eugenol's share of the essential oil, and the oil itself is only about a tenth to a fifth of the bud. Measured in the whole clove, eugenol runs 9,381 to 14,650 milligrams per 100 grams of plant material, still an extraordinary share for one compound in one plant part. Drying moves the number in a direction that surprised the people who first measured it: air-drying and oven-drying near room temperature cost bay leaves almost none of their eugenol, while freezing and freeze-drying lost a substantial share of a leaf's other aroma compounds and, oddly, raised eugenol's own concentration.

On a tongue, eugenol activates TRPV1 and TRPA1, the same receptors capsaicin and mustard use, at a half-maximal concentration of 261.5 micromolar: that is the burn. Separately, in rat trigeminal neurons that test negative for TRPV1, it silences sodium channels directly and, most sensitively of all, shuts down HCN channels at 157 micromolar, which is the numbness that outlasts the burn. The only human trial of it as a toothache remedy tested it on healthy gum before a needle stick, not on an aching tooth, and found it statistically indistinguishable from twenty percent benzocaine; the FDA read that same thin evidence in 1991 and reclassified eugenol from an established toothache remedy to one with insufficient data, a rule that was proposed and never finalized. In this library it is the clove-warm phenol behind four recipes across two kitchens, arriving by way of cloves or allspice depending on the blend.