What is delta-3 carene? The pine-scented terpene

Delta-3-carene (3-carene) is a terpene with a sweet, woody, pine-like smell, found in pine and spruce resin and in hemp. It is a bicyclic monoterpene with the formula C10H16. In conifers it is linked to resistance against insect pests. Studies of its effects are limited to animals and the laboratory.

What is delta-3-carene?

Delta-3-carene is one of the many terpenes that plants use to make their scent and to defend themselves. Like pinene, it is a monoterpene made of two isoprene units folded into two rings, which is why chemists call it bicyclic. The "delta-3" (or Δ3) tells you where the double bond sits in the molecule. In practice, delta-3 carene, 3-carene and carene all refer to the same compound.

What does the carene terpene smell like?

Carene smells sweet, woody and resinous, close to pine or cedar. That makes sense: it is one of the major components of pine tree essential oils (Woo et al., 2019). In cannabis and hemp it is a minor terpene, so it adds a woody note rather than defining the aroma.

Where is 3-carene found?

The richest sources are conifers. Pine and spruce make carene as part of their oleoresin, the sticky resin that seals wounds and repels insects. Rosemary and other herbs are often listed as sources too, in smaller amounts.

A well-studied example is Sitka spruce. Trees that resist the white pine weevil, a beetle that damages young conifers, produced significantly more 3-carene than susceptible trees, which had only trace amounts. The difference traced back to the genes for the enzyme that makes carene (Hall et al., 2011).

Is delta-3-carene found in hemp?

Yes. When researchers distilled the essential oil of hemp, delta-3-carene was one of the measured constituents, alongside beta-pinene, myrcene, limonene and caryophyllene. How finely the plant material was ground and how long it was distilled changed how much carene ended up in the oil (Zheljazkov et al., 2020).

Growing conditions matter too. In a greenhouse study, the light spectrum used to grow cannabis significantly changed terpene concentrations, and levels also differed between flower positions on the same plant (Reichel et al., 2022). That is one reason the terpene profile of a variety is never fixed.

What are the carene terpene effects?

There are no studies of delta-3-carene's effects in people. The research that exists is in animals or in the laboratory:

• Sleep in mice: 3-carene given to mice lengthened sleep in a standard sleep test, acting on the same GABA-A receptor site as some sleeping medicines (Woo et al., 2019).
• Other activity: the same paper notes earlier reports of anti-inflammatory, antimicrobial and anxiety-related effects, again from non-human studies.

So when you read about "carene terpene benefits", keep in mind that these are early findings from mice and cell studies. They do not show that carene in a plant or product has any effect on people.

Does delta-3-carene play a part in the entourage effect?

The entourage effect is the idea that terpenes and cannabinoids act differently together than alone. Carene is sometimes named in this context, but we found no study that tested carene together with cannabinoids. Research on other terpenes has given mixed results, so for carene the question is unanswered.

How can you tell how much carene a plant contains?

Only a laboratory analysis of the terpene profile shows it. Smell is a rough guide at best, because carene usually sits behind more abundant terpenes such as myrcene and caryophyllene.