What do oregano, thyme, cilantro, and bay laurel have in common? Besides being classified as herbs, they all share “chemical signatures” that define them as flavors rather than species. Greek or Turkish oregano (Origanum vulgare subsp. hirtum) shares its fragrant signature of carvacrol with Lippia graveolens and many other species of Origanum. Thyme is characterized by a phenol called thymol that occurs not only in the classic French thyme, Thymus vulgaris, but also in some selections of Origanum. Cilantro is characterized by stinkbug-scented aldehydes, which can also be harvested from species of Coriandrum, Eryngium, Polygonum, or Porophyllum, depending on where you happen to live.
Likewise, bay laurel is a flavor. Around the world, people have local plants that smell and look just like the classic Laurus nobilis and have been used in the same way. The characteristic chemical signature of bay is actually a mixture of three principal chemicals. The leaves contain mostly 1,8-cineole, the same component predominating in eucalyptus (an alternate name of 1,8-cineole is eucalyptol). Alpha-terpinyl acetate, which has a bergamot-lavender scent, and linalool, the main component of lavender, also contribute their nuances. The chemicals blend together to give bay its characteristic spicy fragrance.
In the Mexican bay (Litsea glaucescens), the eucalyptus scent is modified by sabinene, which smells like pine, and terpinen-4-ol, which has a warm, peppery odor.
Leaves of red bay (Persea borbonia) have a substantial amount of 1,8-cineole, but here the bay fragrance is modified by camphor.
Other bays and laurels are used around the world in similar fashion; they include sweet bay (Magnolia virginiana) in North America, bay willow (Salix pentandra) in Europe, and bay rum (Pimenta racemosa) in the West Indies.
California bay (Umbellularia californica) is a different story. Its principal constituent is umbellulone, backed by 1,8-cineole. Umbellulone is toxic to the central nervous system when eaten and causes convulsive sneezing, headaches, and sinus irritation when inhaled deeply. Deer avoid eating it; humans should do the same.