Issn: 1579-4377 Analysis and Toxicological Evaluation of Cannabinoids in Hemp Food Products - a Review

After having abolished the prohibition of the cultivation of the species Cannabis sativa L. (so-called fibre hemp) with minor content of the psychoactive Δ-tetrahydrocannabinol (THC), a wide variety of hemp food products is currently offered on the market. In this review, an introduction to the botany of the hemp plant and the current law situation in Germany and the European Union is presented. A survey of the analytic techniques used to verify compliance with the guidance values is given and the THC content of hemp food products is discussed in regard to its toxicology. In particular, the forensic-toxicological aspects regarding the influence of hemp food on drug tests are described. INTRODUCTION Hemp containing food products are currently experiencing a revival. After the legalization of fibre-hemp cultivation, hemp food products, mostly sold in esoteric stores, were consumed due to supposed psychoactive properties associated with a potential content of Δ-tetrahydrocannabinol (THC). Since the mid 1990s, hemp food has gradually expanded into the natural product market and is increasingly found in natural food stores for positive nutritional and health benefits. In 1995, the first hemp food product on the market was hemp oil [1]. Nowadays various hemp food products are available, e.g. hemp leaves (tea), hemp seeds, hemp oil, flour, beverages (beer, lemonade), and cosmetic products. In the meantime a flourishing trade is establishing itself via the internet. After a short description of the hemp plant and an introduction into hemp foodstuff, the analytical possibilities to determine THC in food samples are described. The THC content of hemp food products is discussed in regard to its toxicology and possible influence on forensic drug tests. HEMP – Cannabis sativa L. The hemp plant Cannabis sativa L. (Cannabaceae), which is a very old culture plant, comes from the restrained wides of Central Asia until Northwest India. Their shoot axis fibres were already used in the second millennium BC in China, especially for the there invented paper manufacturing [2, 3] (Fig. 1). Lachenmeier et al. EJEAFChe, 4(1), 2005. [812-826] Electron. J. Environ. Agric. Food Chem. ISSN 1579-4377 813 Glandular trichomes, especially densely on the underside of the leaves along the leave veins and in the area of the inflorescence, are found on the whole surface of the plant besides seeds and roots. These contain resin consisting from 80 to 90% of cannabinoids as well as essential oils, high-polymeric phenols, terpenes and waxes [4,5]. The cannabinoids belong to the chemical class of terpenophenolic compounds that only occur in the hemp plant. The psychoactive compound is Δ-tetrahydrocannabinol (THC). Besides 60 other known cannabinoids, cannabidiol (CBD) and cannabinol (CBN) are further main components [6] (Fig. 2). In reference to the content of THC, it is possible to distinguish between drug hemp and fibre hemp. The phenotypes of Cannabis sativa are characterized by the ratio of (THC+CBN)/CBD [7-10] (drug hemp > 1; fibre hemp < 1). Recently it was described, that the simultaneous determination of THC, CBD and CBN in hemp containing food products and following calculation of the Cannabis-phenotype-ratio allows the discrimination between fibre and drug hemp, even as a food ingredient [10]. Figure 1. Hemp, Cannabis sativa L., drawing of the plant, inflorescences, fruit and seed (drawing by W. Müller [3]). Tea is made of the leaves of the hemp plant, while flour and oil are made of the seed. The biggest glandular trichomes are found in the bloom regions of the female hemp plant and in particular on the leaves of the seed hulls. The content of cannabinoids correlates with the quantity of the glandular trichomes [4,5]. Generally, all plant parts with the exception of the seeds can contain cannabinoids. Therefore traces of cannabinoids determined in hemp seed products result from contamination with cannabinoid rich plant parts. The concentration of THC in the seeds depends on the type of plant (fibre or drug hemp) as well as on the degree of contamination at the harvest. Therefore, the tidiness of the seeds plays the most decisive part in the concentration of THC in the seeds. The largest proportion of THC can be found on the surface of the seed coat. As a consequence only very low THC concentrations are found in the inside of the seeds (less than 2 mg/kg with drug hemp and less than 0.5 mg/kg with fibre hemp) [11]. For the application as food products it must be made sure that the THC content of the seeds is not increased by impurities, neither with THC-rich plant parts, nor by corresponding cultivation conditions [12]. Especially the flowers of the female plants excrete a cannabinoid-rich resin from the glandular trichomes, that is named hashish (THC-content 0.5-7%), while the inflorescences stuck together with resin are commonly called marihuana (THC-content 5-20%) [2,13]. Drug hemp is usually grown illegally or by chance as a by-product of the cultivation of hemp [2]. Lachenmeier et al. EJEAFChe, 4(1), 2005. [812-826] Electron. J. Environ. Agric. Food Chem. ISSN 1579-4377 814 Because of the drug problem, the breeding of plants with low THC-content was started in France and in the former Soviet-Union in the 1970s, followed by Hungary in the beginning of the 1980s [14]. Present day, fibre hemp species show, in the European Union (EU) guidelines corresponding THC-content of less than 0.2%. Even the selection of phenotypes with less than 0.05% THC was successful [14, 15]. Psychoactive effects with the consumption of fibre hemp plant parts could not be observed [16].