Concentrations of Δ9-THC
In the cannabis plant, Δ9-THC content is highest in the oil from the flowering tops and lowest in the seeds, declining in concentration in the following order: flowering tops > bracts > leaves > stems > roots > seeds (Table 8.1). Cannabis is able to survive in very hot, arid climates because of the resin film that protects it from losing moisture caused by evaporation. This sticky coating is called hashish:
“The means by which cannabis accomplishes this amazing feat is by producing a thick, sticky resin that coats its leaves and flowers. This protective canopy prevents life-sustaining moisture from disappearing into the dry air. But this thick sticky resin is not an ordinary goo. It is the stuff that dreams are made of, the stuff that holds time suspended in limbo, the stuff that makes men forgetful, makes them both sad and deliriously happy, makes them ravenously hungry or completely disinterested in food. It is a god to some and a devil to others. It is all of these things and more. This resin, this shield against the sun, this sticky goo... hashish”
(Abel EL. Marihuana: The First Twelve Thousand Years. Plenum Press, New York, 1980).
The term hashish has an even more interesting derivation and has been related to a particular sect of one of the main branches of Islam (Shiite branch) known as Nizari Ismaili. Led by a famous Islamic dissident, Hasan ibn-Sabah (1050–1124), the movement extended into the period of the Crusades and was marked by terrorist-like secret assassinations of prominent leaders within both Islam and Christianity. Known as the Hashshahin or Heyssessini, two accounts exist which indicate that the followers of this sect may have used cannabis, one by Marco Polo (although he only referred to the drug as an unidentified potion) and another by 12th century friar Arnold von Lubeck (who did refer to it as hemp). Though the state of cannabis intoxication does not lend itself to acts of violence (quite the contrary; see below) the legend begot the name and was embellished by the writings of Marco Polo. Eventually the word assassin came to define a perfidious murderer, and hashish came to be considered a drug that turned normal individuals into assassins. This myth continues to be perpetuated even in modern times. The word hashish itself may have derived from the Arabic asas or “foundation” (which applied to Islam’s religious leaders) and hassas, meaning either “to kill,” or the followers of Hasan ibn-Sabah.
The taxonomic classification of cannabis continues to be in flux, with discussions often referring to either two or three species. The two-species formulation includes Cannabis sativa (not very psychoactive and used mainly for fiber) and Cannabis indica (psychoactive). Another formulation supports a three-species formulation (Cannabis sativa, Cannabis indica, and Cannabis ruderalis). A recent two-species formulation of Cannabis sativa includes all wild, hemp, and drug cannabis races, and Cannabis indica includes cannabis races used for hashish production (also termed Cannabis afghanica; Figure 8.2). For growing hemp for fiber or seeds (sativa or indica), both male and female plants are left undisturbed until harvest. However, in the 1970s, marijuana cultivators in North America and Europe began to grow sinsemilla (Spanish for “without seed”). Sinsemilla preparations can effectively be implemented by eliminating staminate (male) plants from the fields and keeping only the unfertilized pistillate (female) plants to mature for later harvest. The female plants continue to produce flowers, are high in resin glands, and have an increased Δ9-THC content. More recently, indoor plant growing has become popular for growing cannabis for medical purposes. Plants are reproduced vegetatively by rooting cuttings of only female plants, producing uniform crops of seedless females. Marijuana prepared from the dried flowering tops and leaves have Δ9-THC concentrations that average 4.5%. The Δ9-THC of hashish can range from 12.7% to 15.6%. Hash oil is made by soaking cannabis leaves and flowering tops in a solvent such as isopropanol. The plant material is then removed, and the isopropanol that contains the cannabinoids is heated to allow the isopropanol to evaporate, leaving the pure hash oil. It has the highest Δ9-THC concentration of marijuana preparations, reaching 14.1–19.5%. Selective breeding has resulted in special varieties of marijuana, such as sinsemilla and “Netherweed” (Dutch hemp), that may have concentrations as high as 11% (Table 8.2).
FIGURE 8.2 The four major Cannabis gene pools. Most modern medical cannabis varieties are a blend of traditional sativa marijuana varieties with indica hashish varieties. The traditional Cannabis gene pools originate either from Cannabis sativa, which comprises the vast majority of naturally occurring hemp and drug land races, or from Cannabis afghanica from Afghanistan and Pakistan, which is commonly called “indica” and has become a component in many modern drug Cannabis cultivars. Also, all taxonomists recognize the species Cannabis sativa. Schultes et al. (1974) divided Cannabis into three species: Cannabis sativa, Cannabis indica, and Cannabis ruderalis. Clarke and Watson (2002) consider Cannabis sativa to describe all wild hemp and drug Cannabis races with the possible exception of the races used for hashish production in Afghanistan and Pakistan which they term Cannabis afghanica and others refer to as indica. THC, Δ9-tetrahydrocannabinol; CBD, cannabidiol. [Adapted from Clarke RC, Watson DP. Botany of natural Cannabis medicines. In: Grotenhermen F, Russo E (eds) Cannabis and Cannabinoids: Pharmacology, Toxicology and Therapeutic Potential. Haworth Integrative Healing Press, New York, 2002, pp. 3–13.]
Levels of Cannabinoids in Various Plant Parts
Note that variability exists due to methods of analysis, species of plant, and plant origin (see Fetterman PS, Doorenbos NJ, Keith ES, Quimby MW. A simple gas liquid chromatography procedure for determination of cannabinoidic acids in Cannabis sativa L. Experientia, 1971, (27), 988–990.)
A bract is a leaflike plant part, usually small, located just below a flower, a flower stalk, or an inflorescence.
Buds include flowering tops, smaller leaves and seeds.
Fetterman PS, Keith ES, Waller CW, Guerrero O, Doorenbos NJ, Quimby MW. Mississippi-grown Cannabis sativa L: preliminary observation on chemical definition of phenotype and variations in tetrahydrocannabinol content versus age, sex, and plant part. Journal of Pharmaceutical Science, 1971, (60), 1246–1249.
ElSohly MA, Holley JH. Potency Monitoring Project (series title: University of Mississippi Quarterly Report, vol 5). University of Mississippi, Jackson MS, 1983.
Fairbairn JW, Liebmann JA, Simic S. The tetrahydrocannabinol content of cannabis leaf. Journal of Pharmacy and Pharmacology, 1971, (23), 558–559.
Fetterman PS, Doorenbos NJ, Keith ES, Quimby MW. A simple gas liquid chromatography procedure for determination of cannabinoidic acids in Cannabis sativa L. Experientia, 1971a, (27), 988–990.