From Subcools old school organics thread on GreenPassion.

"Cannabis contains over 400 known compounds. Of these, there is a group of about 70 compounds called cannabinoids, made up of molecules with 21 carbon atoms. THC (tetrahydrocannabinol) and CBD (cannabidiol) are the two most prominent cannabinoids and they have been shown in scientific studies to have medical benefits for humans.Another group of compounds in the Cannabis plant are called TERPENOIDS. The terpenoids are made up of repeating units of a 5-carbon compound called isoprene. Terpenoids give marijuana its characteristic aroma. There appears to be over 200 terpenoid compounds in the Cannabis plant.

Plant cannabinoids are found only in the Cannabis plant, but terpenoids are found in countless plant species - about 20,000 terpenoids have been identified by scientists. Terpenoids are considered essential oils. Terpenoids are found in herbs such as mint, sage, citrus peel, some flowers, aromatic barks and woods. Terpenoids are common components of the human diet and are recognized by the FDA as safe for human consumption.

It appears that the terpenoid compounds in marijuana have clinical effects, that is, they work with the cannabinoids to help with symptoms. This is called synergy or the "entourage effect", a term coined by Raphael Mechoulam, a prominent cannabis researcher. Synergy and the entourage effect mean that "the interaction of two or more substances produces combined effects that are greater than the sum of their separate effects".

Here is a list of some of the terpenoids found in cannabis and their clinical effects:

Limonene - this terpenoid is also found in lemons; it works with CBD to give antidepressant effects and stimulates the human immune system; in mice it was found to work with CBD to decrease anxiety and depression; works synergistically with CBD and CBG to kill breast cancer cells; works with THC to decrease GERD (reflux)

Myrcene - this terpenoid is also found in hops; it works with CBD to block inflammation; works as pain-killer in mice studies when combined with CBD and THC; is sedating and was found to potentiate sleep time synergistically with THC

Alpha-pinene - terpenoid also found in pine needles; it works as anti-inflammatory when combined with CBD; bronchodilation (opens lung airways) when combined with THC in human studies; anti-MRSA (Staph infection) with CBD, CBG (cannabigerol) and CBN (cannabinol); works as wide spectrum antibiotic

Linalool - this terpenoid is also found in lavender; has anti-anxiety effects with CBD and maybe CBG; causes sedation in mice studies; works as local anesthetic with THC; anticonvulsant and anti-glutamate with CBD, THCV and CBDV

Nerolidol - this terpenoid is also found in oranges; appears to have sedative qualities; inhibits fungal growth with CBC (cannabichromene)

Beta-caryophyllene - this terpenoid is found in Echinacea; it has anti-inflammatory properties with CBD; protects stomach cells with THC; binds to CB2 receptors with THC giving analgesic and anti-inflammatory properties 

Phytol - this terpenoid is also found in green tea; it appears to block the breakdown of GABA (a neurotransmitter that helps to control anxiety)

Caryophyllene oxide - terpenoid also found in lemon balm; acts as an anti-fungal

The medical effects of the interaction of terpenoids with the cannabinoids is a big area of research and being investigated by many labs. As research is published and our knowledge grows, patients will benefit from being able to select the specific cannabis medication that contain the compounds that work best for their symptoms. More to come....

Thanks to O'Shaughnessy's Journal of Cannabis in Clinical Practice and Dr. Ethan Russo for the information on the terpenoids. Your efforts are most appreciated! "