Variations in Content of Noncannabinoids

2015

Essential Oils

Inevitably, all chemical constituents of marijuana will vary with such factors as genetics, age, sex, and growth conditions. But little research has been done on compounds other than the cannabinoids. The relatively volatile, low molecular weight substances which give plants their characteristic odors can be steam distilled to yield a generally fragrant, oily mixture termed an essential (from essence) oil. About 10% of the contents of the glandular hairs which produce most of the cannabinoids is comprised of the terpene hydrocarbons which make up most of the essential oil. The presence of a high concentration of these compounds in the hairs is yet another bit of evidence to support the notion that they are the biogenetic precursors of the cannabinoids. However, they are likely to be found in significant amounts throughout the cells of the leaves. It should be kept in mind that just as only very small amounts of cannabinoids appear in the essential oil, so will the terpenoids vary in their volatility; that is, the percent of a given compound in the essential oil is not necessarily a precise indicator of its percent of the terpenoids in the intact leaf.

The total yield of essential oil varies between 0.05 and 0.11%, with females and mature plants giving higher yields, at least in some strains. As they are the biogenetic precursors of cannabinoids, the terpenoid contents might be expected to parallel that of the cannabinoids. Males and females seem to have all the same terpenoids (a dozen or so can be easily detected), but the percentage of any given one relative to the others seems to vary at random, with males having more of some and females having more of others. Furthermore, the ratios of the different compounds vary in the different plant parts, with myrcene (for example) being 3.2% of the oil from female flowers, but only 0.8% of that from female leaves, whereas the figures were 6.0 and 1.1% for males (in one study). Corresponding figures for another constituent were 0.6 and 1.6% for females and 1.3 and 0.5% for males. What all this boils down to is that there seems to be no precise correlation between any given terpenoid in the oil and the cannabinoids, and there is probably little hope for establishing any solid correlations of terpenoids with sex, age or seed strain. Nevertheless, we all know that even taking account of variations in curing, the aroma and taste of marijuana varies greatly. Furthermore, the very striking minty odor emitted by some varieties while growing has often been noted. The cannabinoids do not produce the characteristic smell of marijuana when burned, so the essential oils are probably responsible. Besides the caryophyllenes, beta-farnesene, alpha-selinene, beta-phellandrene, limonene and piperidine contribute to the smell of fresh marijuana. Finally, we note once again that there is no evidence that terpenoids have any role in psychic effects of marijuana.

Saturated Hydrocarbons

Short chain saturated hydrocarbons such as propane (three carbon atoms) and butane (four carbon atoms) are familiar to everyone, but every organism contains small amounts of hydrocarbons with longer chains (more carbon atoms). Cannabis is one of many plants with easily detectable amounts of saturated hydrocarbons which have between 25 and 30 carbon atoms per chain. Limited study of these compounds indicates that they show no consistent variation with growth conditions or cannabinoid content. For example, in comparing two high cetrahydrocannabinol types (Thai and South African) with a high cannabidiol type (Turkish), it was found that either or both of the high cetrahydrocannabinol types could be higher, lower, or about equal to the Turkish strain with respect to any one of ten different hydrocarbons, in an apparently random fashion. Likewise, when Brazilian seeds were grown in both Germany and Brazil, it was found that some compounds increased and some decreased in Germany. A survey of a wide variety of samples from around the world showed that some hydrocarbons varied greatly and others varied little. For example, normal pentacosane (25 carbons) ranged from traces in Brazilian samples to 4.3% of the total hydrocarbons in Greek marijuana, while normal nonacosane (29 carbons) varied by only about 30% between any two samples. Much further research will be required to determine whether there is any special significance to these variations.2

Alkaloids

Most of the plant chemicals found in nature which have any striking physiological effects at low dose levels are alkaloids; that is, they are nitrogen-containing compounds with basic (as opposed to acidic) properties. Consequently, it was surprising to find that the active constituent of marijuana was not an alkaloid. Nevertheless, all organisms contain numerous alkaloids in small quantities and a few of these have been isolated in marijuana. The relatively complex alkaloid, cannabisativine, constitutes about 0.001% of the leaves and 0.0005% of the roots of Thai plants, but seems to be absent or present only in traces in high cannabidiol type plants; while the simple alkaloid, hordenine, seems to have an opposite pattern of distribution. Unlike the other constituents discussed here, the alkaloids seem to be correlated with the cannabinoids, at least in the high cetrahydrocannabinol strains. For a high cannabidiol strain, the conditions giving highest cannabidiol concentrations were different from those giving highest alkaloids, but these data are very preliminary. It is extremely unlikely that alkaloids are of any significance as far as marijuana psychoactivity is concerned.

Variations in the Opiate Content of Poppies

In order to help place in proper perspective the mass of data on variations in chemical constituents of marijuana, it may be helpful to very briefly consider some data that have been obtained on opium poppies. There are many strains of poppies which vary greatly in their total yield of opium alkaloids, as well as in their content of any particular alkaloid. In one variety studied in the U.S.S.R., the content of morphine and codeine each varied by a factor of two, and growing conditions which increased morphine decreased codeine. Morphine content decreased as one moved from southern to northern latitudes, while codeine and percentage of total alkaloids increased, but total yield of alkaloids was greatest in the southern latitudes. Evidently, as with cannabinoids, the opium alkaloids increase relatively (i.e., in percent by weight) in response to stress, but total yield is highest when stress is minimal. Likewise, it was discovered that whereas green capsules had the highest morphine concentration five to seven days after flowering, mature, dry capsules collected 33 to 35 days after flowering had the highest total morphine content. A crop yielded 25% more morphine if harvested when mature than at the earlier stage. It was also found that there was 20% greater total yield if the plants were spaced 6 cm apart rather than 12 or 18 cm. Finally, as with Cannabis, it has been found that the seeds do not contain the active constituents.

Selections from the book: “Marijuana Chemistry: Genetics, Processing, & Potency”, 1990.