Updated: Oct 27, 2020
When most people think of oregano, pizza and pasta sauce come to mind. Oregano and marjoram may seem familiar and straightforward to the average cook, but in reality, these common herbs have a very complicated taxonomic history. According to Dr. Arthur O. Tucker, a research professor at Delaware State University specializing in the chemistry and identification of herbs, “it’s best to think of oregano as a flavor rather than a genus or species”.
Origanum is one of over 200 genera in the Lamiaceae (mint family), and the genus includes culinary, fragrant, medicinal and ornamental plants. Herbaceous perennials or subshrubs, origanums are native to the Mediterranean and Eurasia, and grow in mountainous areas with rocky, calcareous soil
Plants from several genera including Lippia and Plectranthus are also considered oreganos due primarily to the presence of the chemical carvacrol, which is largely responsible for oregano’s signature scent and flavor.
According to current estimates there are 44 species, 6 subspecies, 3 varietates (botanical varieties) and 18 naturally occurring hybrids.
Because Origanum taxa are so variable and cross easily, there are hundreds of unclassified hybrids growing in gardens where close proximity encourages crossing that isn’t likely in the wild . Chemistry Origanums have long been valued for their culinary, fragrant and medicinal properties.
These qualities are the result of naturally occurring chemicals in the plant. One source for these qualities is the volatile or “essential” oil. Other plant metabolic chemical products such as fixed oils and flavonoids also contribute.
The composition of the essential oil depends on both the genetics of the plant and where it is grown .
Some species, although beautiful, lack the subjective culinary or fragrance chemistry and are used exclusively as ornamentals. There are two primary chemicals associated with culinary origanums, carvacrol and sabinene hydrate. Carvacrol is the signature chemical largely responsible for the sharp, pungent oregano flavor of Origanum vulgare subsp. hirtum, O. onites, O. minutiflorum and O. syriacum.
Sabinene hydrate is the signature chemical linked to O. majorana’s sweet flavor and can occur heavily in its hybrids with O. vulgare subspecies (O. xmajoricum) . Carvacrol is a creosote-scented phenol with antibacterial and antifungal properties.
Like all plant chemicals, the amount of carvacrol varies depending on the species, subspecies and growing conditions. According to one report, “extreme water stress” can actually increase the amount of carvacrol (and thymol) in the essential oil.
Greek oregano, O. vulgare subsp. hirtum, is valued for its flavor due largely to a high concentration of carvacrol. Some of the other subspecies of O. vulgare, including O. vulgare subsp. vulgare, have little or no carvacrol and do not have the characteristic oregano scent and flavor.
In addition to carvacrol, the essential oil of some Origanum taxa also includes thymol, which produces a thyme-like aroma. Both thymol and carvacrol inhibit the growth of bacteria. The essential oil of the various Origanum species can contain hundreds of additional chemical constituents including linalool, gamma-terpinene, p-cymene and terpinene-4-ol, and scents of the different species and subspecies can include hints of lavender, pine and carnation.
According to an analysis by the USDA, 1 average teaspoon of dried marjoram has 2 calories, .04 grams of fat, .36 grams carbohydrate, .08 grams protein, .2 grams fiber, 12 mg of calcium, 9 mg of potassium and 48 IU vitamin A, plus small amounts of a variety of other vitamins and minerals. The same quantity of dried oregano is slightly more nutritious with 6 calories, .2 grams protein, .18 grams fat, and 1.16 grams carbohydrate and .8 grams fiber. It also contains 28 mg calcium, 30 mg potassium, and 124 IU vitamin A.
In addition to vitamins and minerals, it has been reported that Origanum also includes the flavonoids, galangin and quercetin, which can reduce mutations in the dietary carcinogen.
According to magical folklore, Oregano could be “burned to manifest spirits” or enable astral projection, it is one of the herbs associated with Samhain, a Celtic pagan holiday that is the basis for the secular Halloween, the Plant also has an association with spirits, as it was thought to “help the dead sleep peacefully” if planted on a grave and foretell a happy afterlife if found growing on a grave in Greece.
Both marjoram and wild marjoram/oregano are also reputed to attract wealth when placed in sachets, and marjoram has been used in Sephardic Jewish tradition for healing and to divine the cause of an illness.
download the study made by The Herb Society of America for more: