Cannabis and Its Secondary Metabolites: Their Use As Therapeutic Drugs, Toxicological Aspects, and Analytical Determination
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medicines Review Cannabis and Its Secondary Metabolites: Their Use as Therapeutic Drugs, Toxicological Aspects, and Analytical Determination Joana Gonçalves 1,†, Tiago Rosado 1,†, Sofia Soares 1,†, Ana Y. Simão 1,†,Débora Caramelo 1,†, Ângelo Luís 1,† , Nicolás Fernández 2,†,Mário Barroso 3, Eugenia Gallardo 1 and Ana Paula Duarte 1,* 1 Centro de Investigação em Ciências da Saúde, Faculdade de Ciências da Saúde da Universidade da Beira Interior (CICS-UBI), 6200-506 Covilhã, Portugal; [email protected] (J.G.); [email protected] (T.R.); sofi[email protected] (S.S.); [email protected] (A.Y.S.); [email protected] (D.C.); afl[email protected] (Â.L.); [email protected] (E.G.) 2 Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Cátedra de Toxicología y Química Legal, Laboratorio de Asesoramiento Toxicológico Analítico (CENATOXA). Junín 956 7mo piso. Ciudad Autónoma de Buenos Aires (CABA), Buenos Aires C1113AAD, Argentina; [email protected] 3 Serviço de Química e Toxicologia Forenses, Instituto de Medicina Legal e Ciências Forenses - Delegação do Sul, 1169-201 Lisboa, Portugal; [email protected] * Correspondence: [email protected]; Tel.: +35-127-532-9002 † These authors contributed equally to this work. Received: 31 January 2019; Accepted: 18 February 2019; Published: 23 February 2019 Abstract: Although the medicinal properties of Cannabis species have been known for centuries, the interest on its main active secondary metabolites as therapeutic alternatives for several pathologies has grown in recent years. This potential use has been a revolution worldwide concerning public health, production, use and sale of cannabis, and has led inclusively to legislation changes in some countries. The scientific advances and concerns of the scientific community have allowed a better understanding of cannabis derivatives as pharmacological options in several conditions, such as appetite stimulation, pain treatment, skin pathologies, anticonvulsant therapy, neurodegenerative diseases, and infectious diseases. However, there is some controversy regarding the legal and ethical implications of their use and routes of administration, also concerning the adverse health consequences and deaths attributed to marijuana consumption, and these represent some of the complexities associated with the use of these compounds as therapeutic drugs. This review comprehends the main secondary metabolites of Cannabis, approaching their therapeutic potential and applications, as well as their potential risks, in order to differentiate the consumption as recreational drugs. There will be also a focus on the analytical methodologies for their analysis, in order to aid health professionals and toxicologists in cases where these compounds are present. Keywords: cannabis; cannabinoids; therapeutics; toxicology; analytical determination; legalization 1. Introduction The secondary metabolism of plants plays an important role in their survival in its environment. Secondary metabolites are able to attract pollinators, to defend plants against predators and diseases, and for that reason have been exploited for biopharmaceutical purposes. The secondary metabolites are also present in great amounts in the so-called food plants, conferring them taste, color, and scent. Moreover, numerous plant secondary metabolites such as alkaloids, anthocyanins, flavonoids, Medicines 2019, 6, 31; doi:10.3390/medicines6010031 www.mdpi.com/journal/medicines Medicines 2019, 6, 31 2 of 47 quinones, lignans, steroids, and terpenoids have found commercial applications, namely as drugs, dye, flavor, fragrance, and insecticides [1]. Cannabis sativa L. (Cannabinaceae), also known as marijuana or hemp, belongs to a group of herbaceous shrubs 1 to 2 m in height, and is widely distributed in temperate and tropical areas. Three species are usually recognized: Cannabis sativa, Cannabis indica, and Cannabis ruderalis (the latter may be included under C. sativa), and all may be treated as subspecies of a single species, C. sativa. The plant is accepted as being native from Central Asia. Several preparations of C. sativa including marijuana, hashish, charas, dagga, and bhang, are estimated to be consumed by 200–300 million people around the world [2], being the most popular illicit drug of the 21st century according to the United Nation Office on Drugs and Crime (UNODC) [3]. Cannabis has been cultivated widely in the world for its achene fruits (often wrongly referred to as seeds), which are rich in oils and other phytonutrients, and are frequently used as human food or animal feedstuff, as well as for its fibers, for traditional medicine and spiritual purposes as therapeutic and hallucinogenic drug [2,4]. Cannabis is one of the most consumed drugs worldwide, together with legal drugs such as tobacco, alcohol, and caffeine. Cannabis plants contain more than 545 known compounds. In addition to phytocannabinoids (which are C21 terpenophenolic, or C22 for the carboxylated forms, compounds with physiological and often psychotogenic effects, possessing monoterpene and alkylresorcinol moieties in their molecules [4–6]), they include alkanes, sugars, nitrogenous compounds (such as spermidine alkaloids or muscarine), flavonoids, non-cannabinoid phenols, phenylpropanoids, steroids, fatty acids, approximately 140 different terpenes that are predominantly monoterpenes such as β-myrcene, α- and β-pinene, α-terpinolene, but also sesquiterpenes including β-caryophyllene, di- and triterpenes, as well as various other common compounds [4,5]. Out of over 100 cannabinoids identified so far, the most potent in terms of psychoactive activity is trans-D-9-tetrahydrocannabinol (THC) [7]. Four stereoisomers of THC exist, but only the (–)-trans isomer occurs naturally. Two structurally related substances (D9-tetrahydrocannabinol-2-oic acid and D9-tetrahydrocannabinol-4-oic acid - THCA) are usually also present, sometimes in large amounts. The heat of combustion during smoking converts partly THCA to THC. One isomer which is also active (D8-THC) occurs in much smaller amounts. Other related compounds include cannabidiol (CBD) and cannabinol (CBN), the latter particularly in aged samples, and presenting pharmacological effects different than those attributed to THC (Figure1). All these compounds are collectively known as cannabinoids and, unlike many other psychoactive substances, are not nitrogenous bases [8]. Individual cannabinoids are being developed and identified in Cannabis strains, and their effects on symptoms of illnesses suffered by patients are being studied. The main types of natural cannabinoids belong to the families of the cannabigerol-type, cannabichromene-type, cannabidiol-type, cannabinodiol-type, tetrahydrocannabinol-type, cannabinol-type, cannabitriol-type, cannabielsoin-type, isocannabinoids, cannabicyclol-type, cannabicitran-type, and cannabichromanone-type [9]. Medicines 2019, 6, x FOR PEER REVIEW 3 of 46 Medicines 2019, 6, 31 3 of 47 Figure 1. Some natural cannabinoids from the cannabis plant. THC has been used as an anti-vomiting drug in cancer chemotherapy and as an appetite stimulant, especially for AIDS patients [2]. On the other hand, CBD, the isomer of THC, has no psychotropic effect. However, it possesses aFigure variety 1. 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