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

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.

Keywords: Cannabis sativa L.; stability (HPLC, THC, CBN, CBG); traditional tinctures.

Figure 1

HPLC cannabinoid profile (λ = 214 nm) of 90% tinctures from flowering tops or leaves. (A) Freshly prepared; (B) after 3 months at room temperature/daylight (‘shelf’); (C) after 9 months at 4 °C in the dark (all from flowering tops); (D) after 9 months at 4 °C in the dark from leaves. Cannabigerol (CBG); cannabigerolic acid (CBGA); cannabinol (CBN); cannflavin A (CFL-A); cannflavin B (CFL-B); Δ9-tetrahydrocannabinol (THC); Δ9-tetrahydrocannabinolic acid A (THCA).

Figure 2

HPLC cannabinoid profile of a 40% tincture from flowering tops (λ = 214 nm). (A) Fresh; (B) +3 months ‘shelf’; (C) +3 months ‘fridge’; (D) and 2 h heating at 70 °C; (E) +15 months ‘fridge’.

Figure 3

Profile of fresh tinctures (20%, 40%, 80% EtOH) from cannabis flowering tops. (A) Absolute content in THC_tot, CBG_tot, other cannabinoids (oCAN), and phenolics (TPC); (B) total cannabinoid content (CAN_tot) with relative ratio markers THC_tot/CBG_tot, CANA/CAN, and CAN_tot/TPC (see Table 1); (C) maximum non-toxic concentration (MNTC) in HeLa cells (MTT 24 h, mean ± SEM, n = 3); (D) inhibition of stimulated NF-κB activation (phorbol myristate acetate (PMA) 6 h, mean ± SEM, n = 4). Neutral cannabinoids (CAN); cannabinoid acids (CANA); total cannabinoids (CANtot); cannabigerol + cannabigerolic acid (CBGtot); Δ9-tetrahydrocannabinol + Δ9-tetrahydrocannabinolic acid A + cannabinol (THCtot); total phenolic content (TPC).

Figure 4

Profiles of tinctures from flowering tops (F), leaves (L, GL), or root (R) fresh and after 3 months of ‘fridge’ (4 °C/dark) or ‘shelf’ (15–25 °C/light). CW, cold water macerate; HW, hot water infusion, 40%, 60%, and 90% EtOH macerates.

Figure 5

Comparison of tincture profiles from Cannabis flos vs. folium. (A,B): Relative cannabinoid profile of 40% and 90% tinctures (Δ9-tetrahydrocannabinolic acid A THCA, Δ9-tetrahydrocannabinol (THC), cannabinol (CBN), cannabigerolic acid (CBGA), cannabigerol (CBG), other non-identified cannabinoids oCAN, and cannflavins CFL after 2 days, 3 months (15–25 °C/light), 3, 9, and 15 months (4 °C/dark) storage; (C) Absolute values for THCA, THC, CBN, and their sum (THC_tot) in 60% tinctures from flowering tops and leaves (ground) over 15 months (4 °C/dark). Mean of measurement in triplicate ± SD. Cannabidiol (CBD); cannabidiolic acid (CBDA).

Figure 6

Absolute values for cannabinoids and cannflavins in 40% and 90% tinctures from flowering tops (40% EtOH, 90% EtOH) over 15 months (4 °C/dark).

Figure 7

Absolute profile of 40%, 60%, and 90% tinctures from flowering tops (F) or leaves (L) after 3 months (4 °C/dark—control) and additional pasteurisation (long-term 70 °C/2 h or short-term 80 °C/20 min).