Hemp seeds for weed

Cannabis sativa (Hemp) Seeds, Δ 9 -Tetrahydrocannabinol, and Potential Overdose

1 Center for Molecular Design and Preformulations, Toronto General Hospital Research Institute, University Health Network, Toronto, Canada.

2 Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Canada.

Melissa M. Lewis

1 Center for Molecular Design and Preformulations, Toronto General Hospital Research Institute, University Health Network, Toronto, Canada.

3 Multi-Organ Transplant Program, Toronto General Hospital, University Health Network, Toronto, Canada.

Angelica M. Bello

1 Center for Molecular Design and Preformulations, Toronto General Hospital Research Institute, University Health Network, Toronto, Canada.

2 Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Canada.

Ewa Wasilewski

1 Center for Molecular Design and Preformulations, Toronto General Hospital Research Institute, University Health Network, Toronto, Canada.

3 Multi-Organ Transplant Program, Toronto General Hospital, University Health Network, Toronto, Canada.

Hance A. Clarke

4 Department of Anaesthesia, Faculty of Medicine, University of Toronto, Toronto, Canada.

5 The Pain Research Unit, Department of Anesthesia and Pain Management, Toronto General Hospital, University Health Network, Toronto, Canada.

Lakshmi P. Kotra

1 Center for Molecular Design and Preformulations, Toronto General Hospital Research Institute, University Health Network, Toronto, Canada.

2 Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Canada.

3 Multi-Organ Transplant Program, Toronto General Hospital, University Health Network, Toronto, Canada.

1 Center for Molecular Design and Preformulations, Toronto General Hospital Research Institute, University Health Network, Toronto, Canada.

2 Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Canada.

3 Multi-Organ Transplant Program, Toronto General Hospital, University Health Network, Toronto, Canada.

5 The Pain Research Unit, Department of Anesthesia and Pain Management, Toronto General Hospital, University Health Network, Toronto, Canada.

* Address correspondence to: Lakshmi P. Kotra, BPharm(Hons), PhD, Center for Molecular Design and Preformulations, Toronto General Hospital Research Institute, University Health Network, #5-356, TMDT/MaRS Center, 101 College Street, Toronto, Ontario, Canada M5G 1L7, E-mail: [email protected]

This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Associated Data

Abstract

Introduction: Cannabis sativa (hemp) seeds are popular for their high nutrient content, and strict regulations are in place to limit the amount of potentially harmful phytocannabinoids, especially Δ 9 -tetrahydrocannabinol (Δ 9 -THC). In Canada, this limit is 10 μg of Δ 9 -THC per gram of hemp seeds (10 ppm), and other jurisdictions in the world follow similar guidelines.

Materials and Methods: We investigated three different brands of consumer-grade hemp seeds using four different procedures to extract phytocannabinoids, and quantified total Δ 9 -THC and cannabidiol (CBD).

Discussion: We discovered that Δ 9 -THC concentrations in these hemp seeds could be as high as 1250% of the legal limit, and the amount of phytocannabinoids depended on the extraction procedure employed, Soxhlet extraction being the most efficient across all three brands of seeds. Δ 9 -THC and CBD exhibited significant variations in their estimated concentrations even from the same brand, reflecting the inhomogeneous nature of seeds and variability due to the extraction method, but almost in all cases, Δ 9 -THC concentrations were higher than the legal limit. These quantities of total Δ 9 -THC may reach as high as 3.8 mg per gram of hemp seeds, if one were consuming a 30-g daily recommended amount of hemp seeds, and is a cause for concern for potential toxicity. It is not clear if these high quantities of Δ 9 -THC are due to contamination of the seeds, or any other reason.

Conclusion: Careful consideration of the extraction method is very important for the measurement of cannabinoids in hemp seeds.

Keywords: : cannabidiol, Cannabis sativa seeds, hemp seeds, overdose, phytocannabinoid extraction, tetrahydrocannabinol

Introduction

Cannabis spp. of plants produce a unique class of compounds called cannabinoids. Hemp is a variety of the Cannabis sativa plant species that is grown specifically for the industrial uses of its derived products. 1–3 This plant can be refined into a variety of commercial items, including food, and animal feed. C. sativa species leads to both medical cannabis and industrial hemp, and this species contains the psychoactive component Δ 9 -tetrahydrocannabinol (Δ 9 -THC); these two plants are two distinct strains with unique phytochemical signatures. 1 Hemp has lower concentrations of Δ 9 -THC, thus limiting its psychoactive effects, and its concentration is regulated in the consumer products where hemp is legal. 4,5 The seeds of hemp are rich in unsaturated fats and protein, while containing little to no cholesterol. In fact, a 100 g serving of seeds meets up to 63% of the recommended daily value for protein. 6 Whether in the raw seed form or as a derived product such as cold-pressed seed oil, hemp seeds have become increasingly popular as both food and health supplements; in 2011, the United States alone spent more than $11 million on hemp imports for consumption. In most nutritional food stores and grocery stores, hemp seeds are a staple nowadays, in countries where it is legal.

Hemp seeds produce negligible, if any, quantities of THC endogenously. 7 While food-grade strains of hemp must contain less than 0.3% Δ 9 -THC by weight (whole plant), they may not be free of this compound entirely. During the harvesting process, hemp seeds may become contaminated by material from other parts of the plant (such as the Δ 9 -THC-rich trichomes on flowers) and thus acquire Δ 9 -THC onto their outer shells. 7 Exposure to high concentrations of Δ 9 -THC could lead to psychological events and gastrointestinal disorders, including acute toxic events such as sedation. In Switzerland, four patients suffered psychological and gastrointestinal issues due to consumption of hemp seed oil, which had higher concentrations of Δ 9 -THC, prompting public health inquiry. 8 A recent case of Δ 9 -THC poisoning was reported in a toddler who was on a prescription of hemp seed oil to strengthen the immune system. 9 The toddler exhibited symptoms such as stupor and low stimulatability, which are characteristic of Δ 9 -THC intoxication.

In Canada, the Δ 9 -THC content of hemp products is tightly regulated. 5 The Industrial Hemp Regulation (IHR) Program only permits the importation, exportation, sale, and provision of hemp seeds and its derivatives that contain less than 10 μg of THC per gram of food-grade hemp seeds for consumption. 5 Products that exceed this threshold are regulated similar to medical cannabis under the Controlled Drugs and Substances Act, under Narcotics Control Regulations with strict monitoring. 10

We were interested in investigating various chemical procedures that one could employ to extract natural products, effect of solvents in these extraction methods, and ultimately the estimation of various compounds in the extract. In this context, we were interested in studying the extraction of hemp seeds to estimate the amount of Δ 9 -THC, and if the extraction method could influence the estimation in commercial hemp seed. In this study, we report the extractions and analyses of three food-grade hemp seeds, the potential for underestimation of the controlled substance Δ 9 -THC, and the variability one might encounter due to the differences in extraction efficiencies, and discuss the bearing of these results onto public safety.

Materials and Methods

Materials

Three brands (brand# 1, 2 and 3) of hemp seeds were purchased from local supermarkets in Toronto, Canada, and were used as such in the laboratory experiments. All experiments, including extractions and analyses, were conducted under the appropriate Controlled Drugs Substances Dealer License granted to University Health Network. For ultra performance liquid chromatography (UPLC) analysis, HPLC-grade methanol and MilliQ ® water were used for the preparation of the eluents. A Biotage ® Initiator microwave was employed for all microwave-related experiments. Sample solutions were analyzed on a Waters ® ACQUITY UPLC H-Class System equipped with Quaternary Solvent Manager, Sample Manager FTN, and Acquity UPLC ® BEH column (2.1×50 mm, C18, 1.7 μm). A Waters MS 3100 mass spectrometer was used to monitor the samples in both the positive (ES+) and negative (ES−) modes. The injection plate and column were maintained at 15°C and 40°C, respectively. Cerilliant ® standards for Δ 9 -THC, Δ 9 -tetrahydrocannabinolic acid (Δ 9 -THCA), cannabidiolic acid (CBDA), and CBD were purchased from Sigma-Aldrich ® as Certified Reference Standards in the form of 1.0 mg/mL solutions in methanol or acetonitrile.

Extraction

Four extraction methods were used to extract resins from three brands of food-grade hemp seeds. Each brand of hemp seeds was subjected to each extraction procedure thrice to assess any variability that might arise from the extraction procedure itself. Yields of resin obtained are based on the reweighed seeds.

1. Microwave extraction. Hemp seeds (1 g) were macerated in a mortar using a pestle, reweighed and then transferred into a vial, and suspended in ethanol (10 mL). The vial was sealed and the suspension was heated in a microwave to 150°C with stirring at 900 rpm for 20 min. The suspension was allowed to cool to room temperature and filtered on a pad of Celite ® (2 g) and activated carbon (0.25 g). Solids were washed with additional solvent, and all fractions were concentrated to dryness under reduced pressure at 25°C to obtain a sticky resin (yield: 27–38%).

2. Sonication. Hemp seeds (1 g) were macerated, reweighed, and then transferred to a beaker. The macerated seeds were suspended in ethanol (26 mL), and the suspension was sonicated for 20 min after which the solvent was decanted. The sonication was repeated two additional times, collecting the solvent by decantation, refilling with an equivalent amount of solvent, and a 10-min break between each sonication session. All decanted solvent fractions were combined and filtered on a pad of Celite (1 g) and activated carbon (0.25 g). The solids were washed with additional solvent and concentrated to dryness under reduced pressure at 25°C to obtain a sticky resin (yield: 23–40%).

3. Soxhlet extraction. Hemp seeds (2 or 3 g) were macerated with a mortar and pestle, reweighed, and transferred into a cellulose extraction thimble (43×123 mm; 2 mm thickness). The thimble was placed in a Soxhlet extractor (size: 55/50), and ethanol (350 mL) was added to the extractor and refluxed for 4 h. Crude extract was then cooled to rt, and concentrated to dryness under reduced pressure at 25°C to obtain an oily resin (yield: 24–38%).

4. Supercritical fluid extraction (SFE). Hemp seeds (1 or 2 g) were macerated with a mortar and pestle, reweighed, and transferred to an extraction vessel. The extraction was performed using supercritical CO2 as solvent A and ethanol as solvent B. The photodiode array detector was used to monitor the extract, with the range set to 200–600 nm. The back-pressure regulator was set to 12 MPa for the SFE, and other conditions include the following: flow rate=10 mL/min for both CO2 and slave pumps, and 1 mL/min for the make-up pump; temperature=40°C; and gradient: 0–25 min: solvent A, 100%→50%, and solvent B, 0%→50%; 25–26 min: solvent B, 100%; and 26–30 min: solvent A, 100%. The acquisition time was 30 min and the total run time was 30.2 min. All fractions were combined and concentrated to dryness under reduced pressure at 25°C to obtain the extract as a resin (yield: 31–37%).

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Extracts in the form of concentrated resins were used as such for the analysis and quantification of cannabinoids. A 10 mg/mL stock solution of the resin was prepared with a 70:30 methanol:water solution with 0.1% formic acid. A 100 μL aliquot of the stock solution was then diluted with 100 μL of mobile phase (70% MeOH in water, with 0.1% formic acid) and filtered to obtain a 5 mg/mL sample solution for analysis.

Analysis

Sample injection volume was 10 μL, at a mobile phase flow rate of 0.6 mL/min for a total run time of 6 min. Two mobile phases, water/0.1% formic acid (phase A), and methanol/0.1% formic acid (phase B), were used and gradient conditions were used for elution: 0–4.5 min: 30%→0% phase A and 70%→100% phase B, 4.5→5 min: 100% phase B, and 5→6 min: 30% phase A and 70% phase B. Internal standard was benzophenone (10 μg/mL solution in MeOH), and each sample was spiked with 9.6 μL of internal standard before analysis. Each sample was analyzed in triplicate.

Quantification

Chromatograms were obtained from the 315 ES+ and 357 ES− single ion recordings (SIRs). Signals on the chromatograms at retention times of 2.73 min (Δ 9 -THC) and 1.83 min (CBD) in the ES+ mode as well as 3.48 min (Δ 9 -THCA) and 1.95 min (CBDA) in the ES− mode were integrated to determine the areas-under-the-curves (AUCs) for each phytocannabinoid. In addition, AUC of the internal standard was obtained from the signal at 0.55 min in the 183 ES+ SIR and used in the analyses.

Interpretation

All extracts were analyzed for the concentrations of Δ 9 -THC, Δ 9 -THCA, CBDA, and CBD. Thus, concentration standard curves for Δ 9 -THC, CBD, Δ 9 -THCA, and CBDA were generated using the respective cannabinoid standards of various concentrations and internal standard (Supplementary Fig. S1). These standard curves were used to estimate the concentrations of the above analytes in the extracts. Lower limits of detection for Δ 9 -THC, Δ 9 -THCA, CBD, and CBDA are 1.0, 1.0, 2.5, and 1.0 ng/mL, respectively, and the lower limits of quantitation are 2.5, 2.5, 5.0, and 2.5 ng/mL, respectively.

Results and Discussion

Commercial hemp seeds are marketed for their high nutritional values, but due to their relationship to Cannabis spp. of plants, there is a potential for the presence of phytocannabinoids in these seeds. By regulation, total amount of Δ 9 -THC (whether in its acid form, Δ 9 -THCA, or as neutral Δ 9 -THC) must be less than 10 μg/g of hemp seeds (10 ppm) in Canada, and similar regulations exist in other countries where hemp seeds are legal. Hemp seeds from three brands in local supermarkets were purchased and brought to the laboratory. Each brand of hemp seeds was subjected to four different extraction protocols, and each protocol was repeated thrice to account for any variability due to the extraction procedures and associated errors. In total, 36 extracts were obtained from the three brands and analyzed using UPLC-mass spectrometry to quantify the two major phytocannabinoids, Δ 9 -THC and CBD. We expected the quantity of Δ 9 -THC to be within the regulation limits and CBD to be in relatively higher quantities, as one would expect in hemp seeds. As it is common in the Cannabis spp. plants, majority of phytocannabinoids such as Δ 9 -THC and CBD exist in their carboxylic acid precursor forms, Δ 9 -THCA and CBDA ( Fig. 1 ). Subjecting the extract or resin to high degree of temperature converts these acid precursors into decarboxylated forms, Δ 9 -THC and CBD. However, we calculated the total Δ 9 -THC equivalency (including Δ 9 -THCA and Δ 9 -THC found in each extract) to assess the total concentrations; similar procedure was used for the total concentration of CBD.

Chemical structures of (A) Δ 9 -THC, (B) CBD, (C) Δ 9 -THCA, and (D) CBDA. THCA, tetrahydrocannabinolic acid.

Extraction methods employed in this investigation utilize somewhat different principles to extract the phytocannabinoids from the hemp seeds into the solvent. Microwave-based extraction method used ethanol as the solvent, but at temperatures up to 150°C with stirring; majority of the acid forms, Δ 9 -THCA and CBDA, would be converted into the corresponding neutral forms, Δ 9 -THC and CBD, due to exposure to high temperature. This extraction process is also expected to offer high solubility to the phytocannabinoids due to heating to higher temperatures. Sonication was conducted at an ambient temperature using ethanol as the solvent, and is expected to help release compounds from the plant materials. SFE was conducted using a mixture of supercritical CO2 and ethanol as solvent, at high pressures, but temperature was maintained at 40°C; thus, the extraction efficiency depended on the solubility of phytocannabinoids in supercritical CO2 and ethanol mixture. Most exhaustive extraction, due to high temperature and long extraction time, is likely to be Soxhlet extraction, which was performed at the reflux temperatures in ethanol and for up to 4 h. Among these four methods, one would anticipate the highest yield of phytocannabinoids from Soxhlet extraction. Since ethanol was used in all these extraction methods, differences in extracted quantities of phytocannabinoids can be attributed to the extraction methods themselves.

The concentrations of Δ 9 -THC, Δ 9 -THCA, CBD, and CBDA, along with total Δ 9 -THC (i.e., Δ 9 -THC + Δ 9 -THCA) and total CBD (CBDA + CBD) from each brand of hemp seeds, using each of the four extraction procedures, are shown in Table 1 , and are plotted in Figure 2 . The discussion and interpretations henceforth are in the context of total Δ 9 -THC and total CBD.

Total Δ 9 -THC (green bars) and CBD (blue bars) content (μg/g of hemp seed) in the consumer-grade hemp seeds, in brand# 1 (A), brand# 2 (B), and brand# 3 (C). Legal limit of Δ 9 -THC per gram of hemp seeds (as per Health Canada) is shown as a horizontal red line. CBD, cannabidiol; THC, tetrahydrocannabinol.

Table 1.

Estimated Concentrations of Δ 9 -Tetrahydrocannabinol and Cannabidiol in the Hemp Seeds (in μg/g of Hemp Seeds)

Brand# Extraction method Δ 9 -THC Δ 9 -THCA Total Δ 9 -THC CBD CBDA Total CBD
1 Microwave 95±44 20±11 115±55 224±109 3±3 227±111
Sonication 54±14 16±12 70±26 27±9 197±44 224±51
Soxhlet 66±28 13±4 79±32 60±34 157±68 217±102
SFE 97±33 29±24 126±57 49±13 174±93 223±106
2 Microwave 16±13 1±1 17±14 2±4 1±0 3±4
Sonication 63±96 5±5 68±101 18±27 71±99 89±126
Soxhlet 37±5 17±8 54±13 16±2 69±19 85±21
SFE 63±7 12±5 75±12 13±4 159±27 172±31
3 Microwave 10±4 1±0 11±4 6±9 1±0 7±9
Sonication 13±5 2±1 15±6 8±6 12±8 20±14
Soxhlet 44±7 47±21 91±28 54±36 36±15 90±51
SFE 19±3 4±1 23±4 9±7 13±2 21±9

Total THC and total CBD are the total observed weights of THC and THCA, and CBD and CBDA.

CBD, cannabidiol; CBDA, cannabidiolic acid; THC, tetrahydrocannabinol; THCA, tetrahydrocannabinolic acid.

We observed large standard deviations associated with each extraction of the same brand of seeds. Each extraction was performed thrice to be able to assess the experimental variability during extraction, and based on this large standard deviation, it appears that the extracts could show reasonable variability in the assessed phytocannabinoids, and this deviation may also be due to the nonhomogenous hemp seed bulk material. Either way, these variations warrant the analysis of multiple samples of hemp seed from different parts of the bulk material to assess total amount of phytocannabinoids, as accurately as possible. For brand# 1, all four extraction methods yielded approximately similar phytocannabinoids concentrations, that is, total Δ 9 -THC and CBD ( Fig. 2A ). Total CBD concentration ranged from 217±102 to 227±111 μg/g, and all four methods of extraction viz. microwave-based extraction, sonication, SFE, and Soxhlet extraction yielded similar results. Total CBD is expected to be relatively higher in concentration in hemp seeds and is reflected in these measurements. Total Δ 9 -THC has shown some variation based on the extraction method: sonication and Soxhlet extractions showed the amount of total Δ 9 -THC to be 70±26 and 79±32 μg/g, whereas microwave and SFE extracts showed 115±55 and 126±57 μg/g, respectively ( Table 1 ). At the outset, all four quantities are several fold higher than the regulatory limits on Δ 9 -THC quantities in hemp seeds in Canada (red line in Fig. 2A ), and depending on the method employed for extraction, the estimation of Δ 9 -THC would be 7- to 12-fold higher than the legal limit (10 μg/g of hemp seeds in Canada).

Extractions of brand# 2 hemp seeds exhibited more variance, where total Δ 9 -THC amounts were estimated to be 68±101, 54±13, and 75±12 μg/g of hemp seeds using sonication, Soxhlet, and SFE extractions respectively, all of which are fivefold to sevenfold higher than the permitted limit ( Fig. 2B ), whereas microwave extraction estimated the total Δ 9 -THC content to be 17±14 μg/g only. Variations on the CBD estimates are even more significant, where the variation ranged from 3±4 μg/g (using microwave technology) to 172±31 μg/g (SFE) of hemp seeds. It is interesting to note that a different brand led to a completely different profile in the phytocannabinoid variations (brand# 1 vs. 2), and the results based on the extraction method employed are different as well.

For brand# 3, three extraction methods concurred with the estimation of the phytocannabinoids, viz. microwave extraction, sonication, and SFE estimated the CBD in the rage of 7±9 μg/g to 21±9 μg/g, and total Δ 9 -THC content in the range of 11±4 to 23±4 μg/g hemp seeds ( Fig. 2C ). However, Soxhlet extraction indicated that the amount of CBD and total Δ 9 -THC in brand# 3 hemp seeds to be 90±51 and 91±28 μg/g of hemp seeds, respectively. While the former estimations indicate that total Δ 9 -THC is closer to the legal limit in hemp seeds, the latter method indicated it to be up to nine folds higher than the legal limit, and this is a significant difference. Overall, none of the brands using any of the methods could convincingly be confirmed that the total Δ 9 -THC content is within the legal limits of 10 μg/g of hemp seeds. It is also noted that the phytocannabinoid content exhibited a significant variation even among batches from the same brand, reflecting both the inhomogeneous nature of seeds as well as the variations in quantification based on the extraction process.

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According to Health Canada’s Industrial Hemp Technical Manual, the current approved procedure of Δ 9 -THC quantification in hemp involves the sonication of 3 g of dried leaf powder in hexanes followed by analysis by gas chromatography. 11 There is no mention of testing procedures for any other parts of the hemp plant, including its seeds. Using a similar hexane-sonication procedure, quantification conducted by Ross et al., obtained Δ 9 -THC concentrations of 0–12 μg/g for fiber-type cannabis seeds. 7 In this study, ethanolic extraction using sonication exhibited significant variation from 17% to 92% of the maximum yield across the three brands of hemp seeds. This inconsistency could be attributed to the higher oil content within hemp seeds compared to the rest of plant. Due to hydrophobicity of the Δ 9 -THC molecule, it is expected to partition more strongly into the seed material, leading to the gross underestimation of Δ 9 -THC content by sonication.

In an earlier study, Ross et al. conducted an investigation to determine Δ 9 -THC content in drug- and fiber-type (hemp) cannabis seeds. 7 Hemp seeds in this study were found to contain 0–12 μg Δ 9 -THC per 1 g of seeds, but Δ 9 -THC in drug-type cannabis seeds was in much higher levels (35.6–124 μg/g). It was found that majority of Δ 9 -THC was located on the surface of the seeds, and a wash with chloroform removed upto 90% of Δ 9 -THC. It was suggested that fluctuations in the Δ 9 -THC content of different replicates of the same type of seeds could be the result of the degree of contamination on the outside of the seeds. In this study of consumer-grade hemp seeds acquired from the grocery stores, highly variable, but above the legal limit of, Δ 9 -THC may suggest either contamination by drug-type cannabis seeds or improper washing of the seeds.

Δ 9 -THC primarily undergoes liver metabolism through CYP3A4 and CYP2C9. 16 Due to the polymorphic nature of P450 enzymes, 17,18 people consuming hemp seeds may gradually accumulate Δ 9 -THC due to its slow metabolism or relatively long half-life in the body, leading to potentially higher concentrations. In the report by Chinello et al., Δ 9 -THC concentration in the prescribed hemp seed oil was 0.06%, that is, 0.6 mg of total Δ 9 -THC in 1 g of hemp seed oil, and the child was administered two teaspoons (∼10 mL or 9.2 g) a day for 3 weeks before the incidence of neurological symptoms. 19 This amounts to 5.52 mg total Δ 9 -THC per day, when one consumes 10 mL above hemp seed oil. If one were to compare these total Δ 9 -THC levels, a similar quantity of total Δ 9 -THC (5.52 mg) is contained in ∼44.2 g of hemp seeds (brand# 1, total Δ 9 -THC estimate based on SFE extraction), and this is certainly a normal quantity that consumers may consume as part of their daily food consumption. In people with liver impairment or patients consuming other drugs such as ketoconazole (an inhibitor of CYP3A4) or sulfaphenazole (an inhibitor of CYP2C9), one would expect the metabolism of Δ 9 -THC to be slower, and would be at risk for adverse effects upon the consumption of hemp seeds with higher concentrations of total Δ 9 -THC. 16,20,21 However, we note that the bioavailability of Δ 9 -THC is only 10−20% and could vary if consumed along with fatty food, and such factors would influence the plasma levels of Δ 9 -THC. 22–24

The other major phytocannabinoid in hemp, CBD, is an antagonist of CB1 and CB2 with relatively weak binding affinities. 12 While CBD is not known to exhibit psychoactive properties, CBD can be cyclized into Δ 9 -THC when incubated with artificial gastric juice at 37°C. 25 Given that CBD was present in generally higher amounts than Δ 9 -THC, the conversion of CBD into Δ 9 -THC in the stomach after consumption may further contribute to the psychoactivity of hemp seeds.

Conclusion

In comparison, Soxhlet extraction provided consistently higher yields of Δ 9 -THC, although it takes longer time than other methods for extraction. This suggests the importance of heating and prolonged solvent cycling in extracting phytocannabinoids from lipid-rich materials such as hemp seeds. Δ 9 -THC concentrations of up to 125 μg/g of hemp seed were found in food-grade hemp seeds, and all evaluated brands contained higher amounts than the legal threshold of 10 μg Δ 9 -THC per gram of hemp seeds. Exposure to higher amounts of Δ 9 -THC may cause neurological symptoms especially for poor metabolizers of cannabinoids. It would be presumptuous to conclude the source of this excessive Δ 9 -THC in the consumer-grade hemp seeds, but could be either contamination during harvesting/processing of the seeds or higher levels of biosynthesis, which is unlikely. Current methods for validating Δ 9 -THC content in hemp may be providing lower and/or inconsistent yields for hemp seeds and could lead to the underestimation of Δ 9 -THC content. A more robust extraction methodology such as Soxhlet extraction may be more appropriate for the testing of hemp seed products. One may also consider employing washing of hemp seeds with ethanol or other similar solvents, to remove any contamination to the seeds before packaging; but such change from current practice and new processes must be thoroughly investigated before implementation for consumer marketing. Based on the above findings, it is also recommended that the hemp seeds be analyzed specifically for phytocannabinoid content before release into consumer markets.

What’s the difference between hemp and marijuana?

Cannabis may have a reputation for getting people high, but the cannabis plant has a variety of uses.

Although hemp and marijuana are both classified biologically as cannabis, there are a number of important differences between them. Here we’ll break down the anatomy, history, use, and legality of the hemp plant to get to the heart of not only what distinguishes hemp from marijuana, but also what makes it such a viable, versatile commodity.

What is hemp?

A variety of Cannabis sativa L, hemp is a dioecious plant, which means it can be separated into male and female plants. These plants have served a wide variety of purposes for more than 10,000 years. We get fiber from the plant’s stems, protein from the seeds, oils from the leaves, and oils from the smokable flowers. Hemp fibers can be used to make items including paper, clothing, textiles, rope — even building materials.

Hemp fibers can be used to make items including paper, clothing, textiles, rope — even building materials. Photo by: Gina Coleman/Weedmaps

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The whole hemp plant, from stalk to seed, can also be used to make fuel and feedstock. For more specific applications, hemp can be divided into four categories:

  • Bast fibers
  • Hurds, or shives
  • Leaves and flowers
  • Seeds

Hemp vs. marijuana: Does hemp also have THC?

Hemp produces a broad range of cannabinoids, including tetrahydrocannabinol (THC), the intoxicating cannabinoid in marijuana. However, hemp does not produce enough THC to create intoxicating effects.

Although hemp doesn’t produce a significant amount of THC, it is capable of producing the non-intoxicating cannabinoid cannabidiol (CBD) in high concentrations. In fact, hemp-derived CBD is rapidly becoming one of the most popular forms of the cannabinoid on the market today.

Many countries differentiate hemp from marijuana by the amount of THC produced by the plant. In the US, industrial hemp is defined as Cannabis sativa L. that does not contain more than 0.3% THC. The European Union has set the limit at 0.2%, while in the UK the limit is zero, unless growers have a cultivation license to grow industrial hemp with no more than 0.2% THC.

In the US, industrial hemp is defined as Cannabis sativa L. that does not contain more than 0.3% THC. Photo by: Gina Coleman/Weedmaps

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Can you smoke hemp?

The short answer is yes. Though be aware that while hemp does have trace amounts of intoxicating compounds, that doesn’t mean it will get you high. Hemp plants don’t produce enough THC to have an intoxicating effect. CBD, though technically psychoactive, is a non-intoxicating cannabinoid and won’t produce any form of a euphoric high on its own.

But if the goal isn’t to get an intoxicating high, smoking organic hemp can be an enjoyable and efficient way to experience other cannabinoids like CBD. It’s also never been easier to experiment now that you can find organic hemp flower and pre-rolls online. And while hemp-derived CBD gummies and CBD oil might be all the rage, smoking hemp allows you to self-titrate in real-time — no waiting around for any subtle effects to kick in.

There’s the added bonus of increased bioavailability. Through the act of inhalation, your bloodstream absorbs CBD much faster than it would after eating an edible or using a tincture under your tongue. Your body will also have access to a lot more of the CBD in the smoke or vapor when it’s inhaled. When consumed, a CBD edible goes through the digestive tract, and some of the potency is lost in the process.

For a cleaner burn, consider lighting your hemp flower with hemp wick. Raw hemp wick coated in beeswax offers a slow burn from all-natural materials, which many users say produces a cleaner cannabis flavor than a lighter or match. The more you know.

For a cleaner burn, consider lighting your hemp flower with hemp wick. Photo by: Gina Coleman/Weedmaps

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How are hemp varieties chosen?

Depending on the desired final product, hemp cultivars are chosen based on several factors, including:

  • Stem quality
  • Cannabinoid content
  • Resistance to disease
  • Time to harvest
  • Hemp oil content
  • Seed production per acre

CBD production, in particular, has become a major factor in recent years. As the CBD market continues to grow, more and more cultivars are also being chosen based on their CBD production and unique aromatic, or terpene, profiles.

Hemp-derived CBD oil has skyrocketed in popularity in recent years. Photo by: Gina Coleman/Weedmaps

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What is hemp used for?

CBD oil is extracted from hemp leaves and flowers. More and more people are experimenting with CBD oil extracted from hemp plants as a wellness supplement, hence the ever-growing popularity of CBD-focused cultivation.

Hemp fibers are primarily used for textiles, paper, building materials, and other industrial products. Raw materials such as hurds, or shives, are short woody fibers typically found inside the stalk. They’re used for making bedding materials, absorbents, particleboard, ceiling panels, compost, and other industrial products.

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Bast fibers make up the outer portion of the stalk and are typically split into three categories — primary, or line fiber, secondary, and tow. They are categorized according to their cell strength and cell wall thickness, which will determine the fiber’s strength, durability, and what it can be used for.

How is hemp used as a food product?

Hemp seeds are rich in protein, dietary fiber, vitamins, and minerals. They contain an optimal ratio of omega-6 to omega-3 fatty acids for healthful consumption. A 2008 study also found that hemp proteins are more digestible for humans than common soy protein isolates (SPIs) used in food products. Hemp seeds can be used as food directly or via oil produced from them. Seeds can also be ground up for flour or mixed with water to create hempseed milk.

How is hemp processed?

Processors use many types of processing techniques on hemp seeds and stalks. The technique used depends on the purpose of the final product.

Hemp seeds

Seeds can be consumed whole, or refined by being pressed or crushed to produce hemp seed oil and flour. These seeds are also hulled, or shelled, to make them more palatable. The remaining shells, which are rich in fiber, can also be used for making flour.

Seeds can be consumed whole, or refined by being pressed or crushed to produce hemp seed oil and flour. Photo by: Gina Coleman/Weedmaps

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Hemp stalks

Hemp stalks are processed through decorticating, a multistep method for removing the long fibers from the rest of the plant. This can involve field retting, a process in which the plants are cut and laid out in the field for four to six weeks. During this time, any bacteria on the plant’s surface will break down the outer layer of the stalk. The retted stalks are then dried.

Water retting is another option. The stalks are immediately dried after harvesting then placed in water for a few days. The water softens the outer layer of the stalks and promotes the growth of additional bacteria, accelerating the process. Finally, chemical retting uses acids, bases, and special enzymes to break down the compounds that hold together the strong bast fibers.

How is hemp cultivated differently than marijuana?

Other key differences between hemp and marijuana have to do with cultivation and harvesting. Male hemp plants flower much faster than females and do not produce nearly as much fiber. In stark contrast to marijuana fields, which seek to banish all males, most female hemp fields include sporadically placed males.

Male hemp plants flower much faster than females and do not produce nearly as much fiber. Photo by: Gina Coleman/Weedmaps

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The male hemp plants release pollen female plants use to produce seeds that are either planted for future crops or sold as food. In marijuana fields, male plants are typically eliminated to ensure the maximum production of sinsemilla (seedless) flowers.

While marijuana cultivation requires ample spacing to reduce the risk of mold or bacteria, hemp can be planted more densely. Most marijuana crops are planted with one plant per 4 square feet. Hemp plants that are grown for oil are planted at roughly 40 to 60 plants per 4 square feet. Those grown for fiber are even more densely planted at a rate of about 100 to 120 plants per 4 square feet.

Hemp plants are almost always cultivated outdoors, as opposed to marijuana plants, which are often planted in greenhouses or indoor grow operations. Because hemp is susceptible to the same predators, diseases, and insects that attack marijuana, many cultivators employ a technique called crop rotation, in which alternating crops are planted in the same place, to avoid any buildup of these organisms and to allow nutrients to return to the soil.

The specific order of crop rotation and types of crops being rotated with hemp will depend on the location of the farm. Hemp is also used as a rotational crop at farms where it is not the primary agricultural product.

Is hemp cultivation legal in the U.S.?

Federal action

The 2014 Agricultural Act, more commonly known as the 2014 Farm Bill, includes section 7606, which allows for universities and state departments of agriculture to cultivate industrial hemp, as long as it is cultivated and used for research. Under the 2014 Agricultural act, state departments and universities must also be registered with their state, and defer to state laws and regulations for approval to grow hemp.

As part of the Agriculture Improvement Act of 2018 (aka the 2018 Farm Bill), the Hemp Farming Act of 2018 reclassified hemp (with less than 0.3% THC) from Schedule I, the federal government’s most restrictive classification of controlled substances, which are considered highly prone to abuse and without medicinal benefits. This move to federally legalize hemp allowed for its cultivation and distribution as a legal agricultural product.

Under the Hemp Farming Act, hemp cultivation is no longer limited to state departments and universities. In addition, the act gives hemp farmers the right to water, crop insurance, and federal agricultural grants, as well as legal access to national banking. Hemp may also be transported across state lines.

State laws

Prior to the Hemp Farming Act of 2018, 41 states had passed industrial hemp-related legislation. Thirty-nine of those states legalized statewide cultivation programs that defined hemp specifically to differentiate it from marijuana, establish licensing requirements, and regulate production.

The Hemp Farming Act now requires state departments of agriculture to consult with their governors and chief law enforcement officers on a regulatory program, which will then be submitted to the US Secretary of Agriculture for approval. According to Section 297B of the bill, state hemp regulatory programs must include a system to maintain information on all land where cultivation takes place, procedures for testing THC levels in hemp, and procedures for disposing of products that violate THC content restrictions.

World history of hemp

Hemp has been cultivated on a global scale for thousands of years. The oldest documented evidence of hemp cultivation is a rope, which dates back to 26,900 BCE, found in today’s Czech Republic.

Some of the earliest known prolific uses of hemp began in China about 10,000 BCE, where it was used for making clothing, rope, and paper. The Yangshao people, who lived in China from roughly 5,000 BCE, wove hemp and pressed it into their pottery for decorative purposes. From about 5,000 to 300 BCE, the plant was also grown in Japan and used for fiber and paper.

Cannabis played a large role in the Greco-Roman cultures as a source of fiber, intoxication, and medicine. Cannabis seeds were discovered in the ruins of Pompeii, and Greek rhetorician Athenaeus made note of hemp being used to make rope between 170 and 230 CE. Roman author and naturalist Pliny the Elder also made reference to a cannabis root decoction as a treatment for joint stiffness and gout in the first century BCE.

Exactly how and when hemp originated in the New World is still highly debated. Though long thought to be introduced to the Americas by Christopher Columbus, hemp has been discovered in Native American civilizations that predate Columbus’ arrival. William Henry Holmes’ “Prehistoric Textile Art of Eastern United States” report from 1896 notes hemp from Native American tribes of the Great Lakes and Mississippi Valley.

Hemp products from pre-Columbian native civilizations were also found in Virginia. Vikings, who used the plant for making rope and sails, may also have brought seeds with them when they attempted to colonize the New World.

Jamestown settlers introduced hemp to colonial America in the early 1600s for rope, paper, and other fiber-based products; they even imposed fines on those who didn’t produce the crop themselves. US presidents George Washington and Thomas Jefferson grew hemp.

Hemp was a prominent crop in the United States until 1937, when the Marihuana Tax Act virtually obliterated the American hemp industry. During World War II, the crop saw a resurgence in the US as it was used extensively to make military items including uniforms, canvas, and rope. The Department of Agriculture even released a short documentary, “Hemp for Victory,” in 1942, which promoted the plant as a useful crop for the war cause.

The World War II hemp resurgence was short-lived, though. Until the passing of the 2014 Farm Bill, the Controlled Substances Act of 1970 kept industrial production dormant. Today, hemp is rapidly becoming an indispensable resource for CBD oil and other CBD products.

Frequently asked questions

Is hemp a drug?

Hemp itself is a plant. But CBD, which might be considered a drug, can be made from hemp. The US Food and Drug Administration has approved a CBD-based drug as a treatment for epilepsy. And many people worldwide use CBD products to treat a variety of ailments, though much more research needs to be done on CBD’s efficacy against everything from cancer to acne.

Is hemp legal in Australia?

Certain parts of the hemp plant are legal in Australia. The government has more information.

Is hemp legal in NZ?

The country has a licensing program for those interested in growing certain cultivars of hemp that contain less than 0.35% THC.

What is hemp used for medically?

As stated above, CBD derived from hemp has a variety of uses. The most official is the FDA-approved drug to treat childhood epilepsy. Beyond that, more research needs to be done but scientists are looking at CBD to treat or ease symptoms of:

  • Parkinson’s disease
  • Alzheimer’s disease
  • Cancer
  • Inflammation
  • Pain, including chronic and neuropathic pain
  • Post-traumatic stress disorder (PTSD)
  • Depression
  • Sleep disorders
  • Bipolar Disorder
  • Social Anxiety Disorder

Sources

Wang, Xian-Sheng, et al. “Characterization, Amino Acid Composition and in Vitro Digestibility of Hemp (Cannabis Sativa L.) Proteins.” Food Chemistry , vol. 107, no. 1, 1 Mar. 2008, pp. 11–18., doi:10.1016/j.foodchem.2007.06.064.

Callaway, J. C. “Hempseed as a Nutritional Resource: An Overview.” Euphytica , vol. 140, no. 1-2, 2004, pp. 65–72., doi:10.1007/s10681-004-4811-6.

Ryz, Natasha R., et al. “Cannabis Roots: A Traditional Therapy with Future Potential for Treating Inflammation and Pain.” Cannabis and Cannabinoid Research , vol. 2, no. 1, Jan. 2017, pp. 210–216., doi:10.1089/can.2017.0028.

Holmes, William Henry. Prehistoric Textile Art of Eastern United States . G.P.O., 1896.