Quality Control of Traditional Cannabis Tinctures: Pattern, Markers, and Stability.

Wieland Peschel

doi:10.3390/scipharm84030567

Abstract

Traditional tinctures of Cannabis sativa L. became obsolete before elucidation of the main cannabinoids and routine quality testing for medicines. In view of increasing medicinal use of cannabinoids and associated safety concerns, tinctures from a Δ9-tetrahydrocannabinol (THC)-type chemovar were studied. High-performance liquid chromatography with diode-array detection (HPLC/DAD) was used to determine THC, Δ9-tetrahydrocannabinolic acid A (THCA), cannabinol (CBN), cannabidiol (CBD), cannabidiolic acid (CBDA), cannabigerol (CBG), cannabigerolic acid (CBGA), cannflavin A/B, and total phenolics. Derived group and ratio markers describe absolute and relative profiles when varying plant part (flos, folium), extraction solvent (EtOH percentage), storage conditions (‘shelf’ or ‘fridge’ up to 15 months), and pasteurization (2 h 70 °C, 20 min 80 °C). Tinctures from female flowering tops contained ten-fold more cannabinoids than tinctures from leaves; tinctures (80%–90% EtOH) contained ten-fold more cannabinoids than tinctures (40% EtOH). The analysis of CBGA + CBG, the main co-cannabinoids aside from THCA + THC, appears more relevant than CBDA + CBD. The decarboxylation of THCA to THC—the main change during storage of freshly prepared tinctures—is after 15 months in the ‘fridge’ comparable to 3 months on the ‘shelf’. Minimally increased CBN totals did not correlate to diminished totals of THCA and THC (up to 15% after 3 months ‘shelf’, 45% after 15 months ‘fridge’). Instead, total cannabinoids or acidic/neutral cannabinoid ratios are better stability markers. Moderate changes after pasteurization and partial losses below 10% for total cannabinoids after 9 months ‘fridge’ indicate possibilities for a reasonable shelf life. Yet storage and use of non-stabilized tinctures remain critical without authorized specification and stability data because a consistent cannabinoid content is not guaranteed.

Highlights

In the 19th century, the Irish surgeon O’Shaughnessy reintroduced the use of cannabis from India into Western medicine [1,2]
In the UK for instance, cannabis disappeared from the 1932 British Pharmacopoeia but remained in the 1949 British Pharmaceutical Codex (BPC) and was available for use via prescription until 1971 in form of the substance (Cannabis BPC), an extract, and a ‘tincture’ [4]
The seeds of the Cannabis sativa L. variety ‘northern lights 5 crossed with haze’ were purchased from Pukka Seed Company (Guildford, UK)

Summary

Introduction

In the 19th century, the Irish surgeon O’Shaughnessy reintroduced the use of cannabis from India into Western medicine [1,2]. (Cannabaceae)—largely in the form of ethanolic tinctures—was part of main Western pharmacopoeias until the 1930s, when it was removed gradually with increasing recreational use and its legal prosecution [3]. In the UK for instance, cannabis disappeared from the 1932 British Pharmacopoeia but remained in the 1949 British Pharmaceutical Codex (BPC) and was available for use via prescription until 1971 in form of the substance (Cannabis BPC), an extract (ethanolic percolate), and a ‘tincture’ (dilution of cannabis extract BPC) [4]. The consistent content of traditional tinctures and its analysis is of historic interest—as they remain somewhat popular for non-smokers—but possibly because of its simple preparation and traditional oral use. The specific quality of traditional liquid extracts has not been investigated so far, the knowledge about its variable content is essential for risk assessment and regulation nowadays

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Conclusion