Journal:The cannabis terpenes

Abstract

Terpenes are the primary constituents of essential oils and are responsible for the aroma characteristics of the Cannabis plant. Together with cannabinoids, terpenes illustrate a potential synergic and/or entourage effect, with their interactions having only been speculated on for the last few decades. Hundreds of terpenes have been identified that additionally add to the overall cannabis sensory experience, contributing largely to the consumer’s experiences, as well as the market price. These terpenes also enhance many therapeutic efforts, especially as aromatherapy. To shed light on the importance of terpenes in the cannabis industry, the purpose of this review is to morphologically describe sources of cannabis terpenes and to explain the biosynthesis and diversity of terpene profiles in different cannabis chemotypes.

Introduction

Cannabis sativa L. or Cannabis is a herbaceous annual that has a long history of use around the world as fiber, food, oil, and medicine. Depending on the purpose of utilization, cannabis can be called by different names, for example, “hemp” as a fiber and textile crop, and “recreational cannabis,” also known in the United States as "marijuana." Aside from its quality as an industrial textile, the psychoactive properties have placed a stigma on Cannabis plants as an illicit drug, with many informal names including pot, dope, grass, weed, Mary Jane, bud, hash, bhang, kef, ganja, locoweed, reefer, doob, spliff, toke, and roach. It has been forbidden to grow in many countries due to its psychoactive constituents. From a medical perspective, many recent studies have advised that an increase in cannabis use is associated with psychiatric symptoms, including depression and anxiety. However, many users still exclusively endorse its recreational purpose. As a result, there has been a strong movement toward correcting negative attitudes about Cannabis, and attempts have been made in trying to remove this plant from narcotic lists. In Thailand, for instance, as of 2020, cannabis strains such as กัญชง (hemp) and กัญชา (marijuana) are legally grown for industrial fiber or medicinal purposes based on the controlled level of active metabolites, including cannabinoids such as Δ⁹–tetrahydrocannabinol (THC) and cannabidiol (CBD). While primary focus has been paid to the bioactive functions of the cannabinoids, the hydrocarbon terpenes could also potentially offer interesting entourage effects that could ideally synergize or downstream their effects. Eminently, with the rise in the legal cannabis industry, interest has grown around cannabis terpenes as they contribute many of the different aromatic characteristics that influence the diverse varieties of cannabis strains.

Within the scope of this review, we provide the general background history of cannabis discovery and the importance of terpenes. The taxonomy and morphology of cannabis, particularly in regards to the localization of its terpenes, are discussed. More importantly, the chemistry, biosynthesis, and diversity of terpenes in different cannabis genotypes are of major interest in this review.

The cannabis discovery and its importance as a source of terpene

Cannabis has a long history dating back approximately to just after the Ice Age, as cord and textile scraps made of cannabis fiber have been found in historic caves in the Czech Republic. In the nineteenth century, the plant was recorded as originating near the southern area of the Caspian Sea near Iran (Figure 1b). It was later confirmed by the chemotaxonomy of the essential oil from cannabis of diverse origins, and most of the cannabis phenotypes collected around the globe had chemical ingredients similar to those of Central Asian origin. In previous days, it was known as the original fiber plant in Asian culture. Seed and seed oil extracts were also used as food. The first record of cannabis in the literature in China can be dated to approximately 5,000 years ago, as written by emperor Chen Nong, who was then known as the father of Chinese agriculture. The Chinese alphabet's “Ma” was created using the mimic of the cannabis drying process (Figure 1a). The letter was adjusted to describe the male plant, “his” separated from the female plant, “chu” for the quality of the fiber. In 500 BC, the use of cannabis spread worldwide from Asia to Europe and to Africa through the silk road. In the nineteenth century, hemp was popular in the western world as a fiber crop that had superior qualities. It is not too surprising therefore that cannabis is today known as an ideal plant in terms of sustainability. In a period of rapid industrial growth, hemp became the industrial crop as countries raced against one another toward modernity. In addition to the world textile industry, the plant began to be known for its medical uses. It was believed that during the nineteenth century, there were thousands of cannabis medicines available, produced by more than 280 manufacturers. However, the growth and interest in this fiber crop crashed after the attempt to add it to the narcotic list with opium during the 1925 International Opium Convention in Geneva.

Fig. 1 The evolution of the Chinese characters of the word “Cannabis sativa” or “Ma” (a), and the place of origin of the cannabis plant in the southern Caspian sea near Iran (b)

The first cannabinoid isolates used for medicinal purposes were produced in Czechoslovakia, and CBD was fully characterized for the first time in 1963, followed by the psychoactive THC in the following year. The discovery of cannabinoid receptors, CB1 and CB2, together with the full comprehension of the endocannabinoid system, helped us recognize the medicinal benefits of this plant. In 1942, Simonsen and Todd were the first researchers to separate terpene fractions from cannabinoids in the literature, and p-Cymene was reported as a main constituent from Egyptian hashish. Only in the past years have the terms "synergic" and "entourage effect" appeared in speculations by chemists all over the world in relation to cannabis compounds, included the terpenes. The proposed synergies were first described as routes for the molecular regulation of endogenous cannabinoid activity. Russo later proposed the unique therapeutic effect of cannabis terpenes that possibly play a role on the entourage effects of the medicinal properties of the cannabinoids. This phytocannabinoid-terpenoid synergy could potentially enhance the treatments of pain, inflammation, depression, anxiety, addiction, epilepsy, cancer, fungal, and bacterial infections.

Notes

This presentation is faithful to the original, with only a few minor changes to presentation. Some grammar and punctuation was cleaned up to improve readability. In some cases important information was missing from the references, and that information was added.