Journal:A sustainable approach for the reliable and simultaneous determination of terpenoids and cannabinoids in hemp inflorescences by vacuum-assisted headspace solid-phase microextraction
| Full article title | A sustainable approach for the reliable and simultaneous determination of terpenoids and cannabinoids in hemp inflorescences by vacuum-assisted headspace solid-phase microextraction |
|---|---|
| Journal | Advances in Sample Preparation |
| Author(s) | Capetti, Francesca; Rubiolo, Patrizia; Mastellone, Giulia; Marengo, Arianna; Sgorbini, Barbara; Cagliero, Cecilia |
| Author affiliation(s) | Università di Torino |
| Primary contact | Email: cecilia dot cagliero at unito dot it |
| Year published | 2022 |
| Volume and issue | 2 |
| Article # | 100014 |
| DOI | 10.1016/j.sampre.2022.100014 |
| ISSN | 2772-5820 |
| Distribution license | Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International |
| Website | https://www.sciencedirect.com/science/article/pii/S2772582022000110 |
| Download | https://www.sciencedirect.com/science/article/pii/S2772582022000110/pdfft (PDF) |
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Abstract
Cannabis sativa L. is an intriguing plant that has been exploited since ancient times for recreational, medical, textile and food purposes. The plant's most promising bioactive constituents discovered so far belong to the terpenoid and cannabinoid classes. These specialized metabolites are highly concentrated in the plant aerial parts, and their chemical characterization is crucial to guarantee the safe and efficient use of the plant material irrespective of which use it is.
This study investigates for the first time the use of vacuum-assisted headspace solid-phase microextraction (Vac-HSSPME) as a sample preparation process in an analytical protocol based on Vac-HSSPME combined to fast gas chromatography–mass spectrometry (GC-MS) analysis that aims at comprehensively characterising both the terpenoid and cannabinoid profiles of Cannabis inflorescences in a single step. The results proved that vacuum in the headspace should be preferred over atmospheric pressure conditions as it ensures the fast recovery of cannabinoid markers at relatively lower sampling temperatures (i.e., 90°C) that do not discriminate the most volatile fraction nor cause the formation of artifacts when the sampling time is minimized.
Keywords: Cannabis sativa inflorescences, vacuum-assisted headspace solid-phase microextraction, volatilome, terpenoids, cannabinoids
Introduction
Cannabis sativa L. currently can be considered one of the most studied plants due to its relevance in the illicit drug market and in the textile and food industry [1], as well as its potential medical usage. Whether the plant is intended for recreational purposes, fiber production (hemp), or medical use depends on the content of two major cannabinoids in the aerial parts of the plant: the psychoactive (-)-trans-Δ9-tetrahydrocannabinol (Δ9-THC) and cannabidiol (CBD), the latter displaying several biological activities but not the psychotropic one. [2,3] The illicit drug chemotype, also known as type I, contains an excess of Δ9-THC and a limited amount of CBD. Contrary to that is the cannabis chemotype used in manufacturing (i.e., industrial hemp or type III), where the ratio is reversed and Δ9-THC content cannot exceed 0.2%. Finally, the type II chemotype, which is used for medical purposes, is defined as having high mean contents of both CBD and Δ9-THC (i.e., Bedrocan: 22% THC, <1% CBD; Bediol: 6.5% THC, 8% CBD). [3][4][5]
Other than Δ9-THC and CBD, the plant may synthesize several specialised metabolites, including additional phytocannabinoids and terpenes, amongst others [6], which are both produced by stalked glandular trichomes that are highly concentrated on female inflorescences. [7] Phytocannabinoids are C21 compounds known as terpenophenolic compounds. They are produced by the plant in their acidic form, which under heating or during storage is decarboxylated into the active neutral form. [6] At least 104 cannabinoids have been isolated so far. [8] Aside from Δ9-THC, CBD, cannabichromene (CBC), and cannabigerol (CBG), other predominant secondary metabolites are Δ9-tetrahydrocannabinolic acid (Δ9-THCA), cannabidiolic acid (CBDA), cannabichromenic acid (CBCA), and cannabigerolic acid (CBGA), which are the precursors of the formerly mentioned compounds. Other minor cannabinoids include cannabinolic acid (CBNA) and Δ8THCA, which are artifacts of Δ9THCA, as well as cannabielsoic acid (CBEA) and cannabinodiolic acid (CBNDA), which derive from CBDA. [9]
Terpenes are cannabis's most abundant specialized metabolites, including at least 120 identified terpenoids. [8] Literature data suggest that varying pharmaceutical properties between different Cannabis varieties can be attributed to synergistic interactions, known as the "entourage effect," between cannabinoids and terpenes. [9] A comprehensive qualitative characterisation of both the cannabinoid and terpene profiles of the plant raw material is therefore of utmost importance not only to define its rational use (i.e., whether the plant under investigation was cultivated for fiber production, medical, or drug purposes) but also to guarantee the efficacy and safety of its potential pharmaceutical application.
The most employed method of extraction of cannabinoids from plant raw material is solid-liquid extraction (SLE) using ethanol or acetone as extracting solvents due to their affinity and consequent high extracting efficiency for cannabinoids. [10,11] High-performance liquid chromatography (HPLC) and gas chromatography (GC) coupled to mass spectrometry are the analytical techniques of choice for many qualitative and quantitative analyses. [11] HPLC is usually employed when the acid and the neutral form of the investigated cannabinoids must be measured separately, while GC analyses enable the characterization of the total cannabinoid content (e.g. the combined amount of THC and THCA), as GC systems, by definition, work with high temperatures that lead unavoidably to the decarboxylation of cannabinoid acids. [11] The total cannabinoid content is usually measured as it best represents the pharmacological activity of the material, unless differently stated by legislation. [12]
Thanks to their volatile nature, the isolation of terpenes—and in particular of mono- and sesquiterpenes—from plant raw material is straightforward, and their profiling can be performed by headspace solid-phase microextraction (HS-SPME) online combined to GC-MS analysis [5].
Abbreviations, acronyms, and initialisms
- Δ9-THC: Δ9-tetrahydrocannabinol
- Δ9-THCA: Δ9-tetrahydrocannabinolic acid
- CBC: cannabichromene
- CBCA: cannabichromenic acid
- CBD: cannabidiol
- CBDA: cannabidiolic acid
- CBEA: cannabielsoic acid
- CBG: cannabigerol
- CBGA: cannabigerolic acid
- CBNA: cannabinolic acid
- CBNDA: cannabinodiolic acid
- GC: gas chromatography
- HPLC: high-performance liquid chromatography
- SLE: solid-liquid extraction
- Vac-HSSPME: vacuum-assisted headspace solid-phase microextraction
References
Notes
This presentation is faithful to the original, with only a few minor changes to presentation. Some grammar and punctuation was cleaned up to improve readability. In some cases important information was missing from the references, and that information was added. Nothing else was changed in accordance with the NoDerivatives portion of the license.
