One thing many people notice about cannabis is the smell, which varies a lot from strain to strain. Contrary to popular belief the cannabinoids in cannabis, like THC, have no smell and the unique fragrance of various cannabis strains is actually 

One thing many people notice about cannabis is the smell, which varies a lot from strain to strain. Contrary to popular belief the cannabinoids in cannabis, like THC, have no smell and the unique fragrance of various cannabis strains is actually dictated by the Terpenes. 

Terpenes, or Terpenoids as they otherwise called, are what gives cannabis its smell. Unlike Cannabinoids which are virtually exclusive to the cannabis plant, Terpenes are also found in other plants. In addition to providing the aroma of cannabis, terpenes have various therapeutic properties of their own and can also provide synergistic effects with the naturally present cannabinoids, contributing to the entourage effect.
Though there are many more terpenes present in cannabis the most well known are listed below along with the numerous therapeutic properties they can potentially provide.

Alpha-Pinene and Beta-Pinene
These terpenes are also found in pine needles, rosemary, basil, parsley and dill and unsurprisingly give cannabis a pine like effect. Like many terpenoids the medical value is yet to be fully explored but it has been established as an antiseptic and is useful at relieving the effects of Asthma. Vaporising cannabis is primarily a good medicine for asthma because of the bronchial dilating effects of THC, but cannabis with Alpha or Beta Pinene in high amounts is considered to be even more effective as an medicine for Asthma.
This terpenoid is also known to counter the psychoactive effects of THC and mediate the high in a similar manner to CBD. It is also considered to be good for memory and makes users feel more alert, something which can counter the sedative effects of many cannabis strains, particularly those with high CBN content.

Myrcene
This terpenoid is also found in mangos, lemongrass, thyme and hops. It has a musky, earthy, herbal smell with hints of citrus. Cannabis with a high Myrcene content is considered better for relaxing as it has a more sedative and relaxing effect. While research is limited this terpenoid is known to have anti-oxidant and anti-inflammatory properties and has shown some anti-carcinogenic (anti-cancer) effects. It is also being looked at for its potential as an anti-depressant and is useful for pain relief and aiding sleep. Like with other terpenoids it has an effect on the overall entourage effect of cannabis and aids the effects of cannabis when treating inflammation or insomnia.

Limonene
This terpenoid is also found in fruit rinds (skin) and is particularly abundant in lemons, it is also found in rosemary, juniper and peppermint. Its aroma is basically a citrus like smell and is the primary terpenoid found in cannabis that has a strong citrus smell to it, especially lemon varieties like Lemon Haze. Cannabis with a high limonene content is very good for stress relief and is found to be very good at elevating mood making it useful for treating depression. It has anti-fungal, anti-bacterial and anti-carcinogenic effects. It can also be used to treat heartburn, depression, dissolve gallstones and is being looked at for its potential to treat gastrointestinal problems. It also appears to enhance the effects of THC and contributes to the entourage effect in a manner that appears to increase the psychoactive effects of THC.

Caryophyllene
This terpenoid is also found in many natural sources including black pepper, lavender, basil, cloves, hops, Oregano, true cinnamon, rosemary, west African pepper and black caraway. Its smell is a peppery and mildly spicy aroma. While it appears to have no noticeable effects to the user on its own it is believed to moderate the psychoactive effects of THC and is especially useful at relieving anxiety. It is the subject of a lot of research and interest with regards to its various medical properties.
Unlike other terpenoids, caryophyllene has some affinity with the cannabinoid receptor CB2, though has no effect on CB1. Though it is not listed as an actual cannabinoid it is under investigation for its potential to mimic the effects of cannabinoids that utilise the CB2 receptor. So far the activation of CB2 has only been established in mice and is yet to be proven in humans, however the potential for it to modulate the Endo Cannabinoid System via the CB2 pathway makes it a subject of great interest as an anxiolytic, anti-depressant, neuroprotective and anti-inflammatory compound. It may also have some cancer killing properties as both THC and CBD have been shown to exert anti cancer effects through activation of the CB2 receptor, however in the case of caryophyllene this particular property has yet to be demonstrated in pre-clinical investigations.

Linalool
Also found in Lavender, it has a lavender like smell characterised as a floral smell with hints of citrus. It is not very well research but is believed to be good at relieving anxiety and is mildly sedative, which makes it useful for aiding sleep. It’s presence in cannabis appears to contribute to the relaxing effects and enhances its use as an anti-depressant.

A Bisabolol
Is a more rare terpenoid and is not found in significant quantities in any other known plant apart from German chamomile, though has been synthesised. It has been shown to induce apoptosis in leukemia cells in vitro which makes it a compound of interest in developing selective cancer treatments. It has a very mild but sweet floral smell to it and has been used in many skin products for its believed skin healing properties. It is considered an anti-irritant, anti-microbial and anti-inflammatory.

Terpenine
Terpenine is technically a blanket term for a small variety of chemicals. A terpenine is found naturally in significant quantities in cumin. B terpenine is only found in synthetic form and is created from the naturally occurring monoterpine Sabinine which is found in black pepper and carrot seed, among other sources.
Terpenine is used in perfume and as in flavourings. Though it is used in the pharmaceutical industry it has no established therapeutic properties.

While research into the therapeutic effects of cannabinoids, especially the raw cannabinoid acids, is limited outside of the better known cannabinoids like THC and CBD, which themselves have had research restricted, the terpenoids have even less research dedicated to them currently, despite the lack of legal restriction that applies to the cannabinoids.
Though some therapeutic value has been established and experienced with most of the terpenes it is only really Caryophyllene that has a significant amount of research into its biological activity and as a result it is this particular terpene that will likely to be developed for medicinal use first. Though it must be noted that Limonene, Myrcene and both Alpha and Beta-Pinene have all shown great promise both for their standalone therapeutic potential and their potential to enhance or mediate the effects of the cannabinoids and cannabinoid acids found naturally in cannabis.

The cannabinoids remain the most medicinally recognised components of the plant, with the decarboxylated cannabinoids more established than their acidic precursors, and with THC and CBD the most medicinally established cannabinoids to date. But while the other cannabinoids and cannabinoid acids are proving to be of great interest for their medical applications the terpenoids also appear to play a role in the therapeutic potential of cannabis medicines and just as cannabinoid profiles are proving to be important for different medicinal applications the terpenoid profile of various cannabis strains may also prove to be of great importance in maximising therapeutic efficacy.