Terpenes and Terpenoids: How to Read This Shelf

The nomenclature, kept straight

Terpenes are hydrocarbons assembled from five-carbon isoprene units: monoterpenes from two (C10), sesquiterpenes from three (C15), diterpenes from four (C20), triterpenes from six (C30). A terpenoid is a terpene that carries oxygen — an alcohol, an ether, a ketone, an aldehyde or an epoxide. The distinction matters analytically and practically: adding oxygen raises the molar mass and the boiling point and usually raises water solubility, which is why 1,8-cineole (a cyclic ether, C10H18O) behaves differently in a hydrosol than alpha-pinene (a bicyclic hydrocarbon, C10H16) even though both are monoterpene-class and both come out of the same distillation. Terpenes in cannabis are products of the plastidial and cytosolic isoprenoid pathways acting on terpene synthase genes; the chemovar differences that the market calls strain differences are largely allelic differences in those synthases plus growing and curing conditions.

Sources: Booth JK 2019 · Russo EB 2011

The single most common misreading of a terpene table

An essential-oil composition figure is a percentage OF THE VOLATILE FRACTION, not of the plant. When a source says Helichrysum odoratissimum is 17.44 percent 1,8-cineole, it means 1,8-cineole was 17.44 percent of the oil recovered by distillation — and the oil yield of that material was on the order of 0.15 to 0.25 percent of the dried herb. So 1,8-cineole is on the order of 0.03 to 0.04 percent of the plant, not 17 percent of it. Marketing copy routinely collapses this distinction and it is the single most frequent error in consumer-facing terpene tables. A cannabis certificate of analysis is usually the opposite convention — terpenes reported as percent w/w or mg/g of the flower or the concentrate itself — so the two kinds of number are not comparable without saying which basis is in use. Always look for the basis line on the report.

• Essential-oil analysis: percent of the recovered volatile oil. Denominator is the oil.
• Cannabis COA terpene panel: percent w/w or mg/g of the sample. Denominator is the product.
• Yield converts between them, and yield is rarely printed next to the composition.

Sources: Van Kush Family Research Institute (operator) 2026* · Lourens ACU 2008

Chemotype variance: why one number is never the answer contested

Terpene composition within a single named species varies by population, chemotype, plant part, harvest timing, drying regime and distillation parameters. South African Helichrysum is a worked example: alpha-pinene is reported up to 43 percent of the oil in H. odoratissimum and at 29.82 percent in H. cymosum, with the sesquiterpene and ketone profiles differing enough between species that faurinone dominates H. petiolare while (E)-caryophyllene dominates H. cymosum. The same is true of cannabis, where two plants sold under one cultivar name can differ severalfold in a given terpene. Treat every percentage in this shelf as one reported analysis of one population, not a species constant. Where a range is known, the range is given.

Contested — caveat. Single-analysis chemotype figures. Any one number here describes the specific sampled material, not the species. Ranges in published reviews are frequently wider than the operator figures quoted alongside them.

Sources: Van Kush Family Research Institute (operator) 2026* · Lourens ACU 2008 · Booth JK 2019

What the pharmacology actually supports, and what it does not contested in vitro

The honest state of the evidence, compound by compound, is uneven. One terpene has a clean, replicated, mechanistically specific receptor finding at physiologically plausible concentration: beta-caryophyllene at CB2. Several have solid animal behavioural or anti-inflammatory data with mechanism partly characterised: myrcene, linalool, alpha-humulene, 1,8-cineole. Several have in-vitro enzyme findings at concentrations far above anything a human achieves from inhaling or eating the plant: much of the acetylcholinesterase and cytochrome-P450 literature falls here. And two compounds on this shelf, faurinone and gamma-curcumene, have essentially no dedicated pharmacology at all. The entourage effect — the claim that terpenes modify cannabinoid effect at the receptor — is genuinely contested: Santiago and colleagues found no modulation of THC activity at human CB1 or CB2 by the common cannabis terpenoids, while LaVigne and colleagues reported cannabimimetic and additive effects for several of the same compounds in a different assay system. Both are in vitro. Neither settles the human question. This shelf marks these sections contested rather than picking a side.

Contested — caveat. The entourage effect is an open question with directly conflicting in-vitro results (Santiago 2019 negative, LaVigne 2021 positive) and no adequate human pharmacodynamic study. Confident claims in either direction are ahead of the data.

Sources: Gertsch J 2008 · Santiago M 2019 · LaVigne JE 2021 · Russo EB 2011

Boiling point is not a vaporizer setting

Every monograph on this shelf reports two different temperatures and they are not the same thing. The boiling point is a physical constant of the pure compound at one atmosphere. The vaporization band is an empirical, device-dependent range over which that compound is observed to come off plant material in a dry-herb vaporizer — lower than the neat boiling point, because the compound is a dilute component of a mixture and evaporates from a matrix at partial pressure rather than boiling. A vaporizer dial reading 175 degrees Celsius is also not a statement that the material is at 175 degrees Celsius. See the vaporization-bands page for the full treatment.

Sources: Lanz C 2016 · Van Kush Family Research Institute (operator) 2026* · Compiled from public compound databases (PubChem 2026*

Corrections made to the operator archive

The 2016 Van Kush terpene notes in this repo (knowledge/herbs/terpenes.json) are the ancestor of this shelf and are right about more than they are wrong about. Four claims in them do not survive the current literature and are corrected here rather than quietly dropped, because the same four claims are extremely widespread and a reader will meet them again elsewhere. In short: beta-caryophyllene is a selective CB2 agonist, not a CB1 ligand; the compound associated with canine cannabis detection in the literature is caryophyllene oxide, not beta-caryophyllene itself; limonene is not called biphenyl and is not a limonoid; and beta-caryophyllene holds GRAS status as a flavouring, which is not the same thing as FDA approval of a cannabinoid. The full corrections, with sources, are on the beta-caryophyllene and limonene pages.

Sources: marsresident / Van Kush Family (operator) 2016* · Gertsch J 2008 · Russo EB 2011