Thermal decarboxylation of acidic cannabinoids in Cannabis species: identification of transformed cannabinoids by UHPLC-Q/TOF–MS

Abstract

Decarboxylation of cannabidiolic acid (CBDA) is an important step for efficient production of the active pharmaceutical component cannabidiol (CBD) in Cannabis species. Acidic cannabinoids (ACBs) can be easily transformed into neutral cannabinoids via loss of carbon dioxide when exposed to heat. During the thermal process, several transformed products including psychotropic △9-tetrahydrocannabinol (△9-THC) and its isomers were produced through decarboxylation, hydration, isomerization, and oxidation, as identified by ultra-high-performance liquid chromatography quadrupole/time-of-flight mass spectrometry (UHPLC-Q/TOF MS). Their identification was carried out using authenticated standards and interpreting the MS/MS fragmentations. To investigate thermal decarboxylation, CBDA was extracted and isolated from inflorescence of Cannabis by ultrasonication extraction and two-step column chromatography. To investigate the decarboxylation yield of isolated CBDA and ACBs in Cannabis extract, samples were examined over a range of reaction temperatures (110–130 °C) and times (5–60 min). Time profiles of CBDA degradation and CBD formation were obtained as functions of the reaction temperature. In particular, most of the CBDA was converted into CBD at 130 °C for 20 min; this CBD was partially transformed to psychotropic THC isomers via cyclization. In addition to THC isomers, cannabielsoin acid (CBEA) and cannabielsoin (CBE) were also observed as minor oxidative transformed products. Based on structural identification and profiling data, thermal transformation pathways of CBDA are plausibly suggested. The results of decarboxylation of ACBs will provide important information on production of neutral cannabinoids, especially CBD, in Cannabis plants and quality control of Cannabis-based products in pharmaceutical and cosmetic industries.

Cannabinoid Biosynthesis Using Noncanonical Cannabinoid Synthases

“…CBEA (7) is different from the rest of the carboxylated products in Scheme 1 due to an additional oxygen atom; CBE (8) is the decarboxylated product of CBEA (7) and has previously been reported as an oxidative product from CBDA (3) [ 15 ]. Analogous to previously determined oxidative cyclization mechanisms of CBGA (1) , we propose that it begins with the formation of the carbocation in the monoterpene moiety and the corresponding reduction of FAD to FADH 2 ( Scheme 4 ).…”

Progress in the analysis of phytocannabinoids by HPLC and UPLC (or UHPLC) during 2020–2023

“…Several UPLC or UHPLC-based methods have been presented in the literature for the analysis of cannabinoids in inflorescences of C. sativa. [77][78][79][80][81][82][83][84] Like the HPLC analyses outlined above, both PDA or DAD and MS detection technologies have been used with UPLC or UHPLC systems. However, the use of MS detection appears to be more popular with UPLC or UHPLC systems for the analysis of inflorescences for phytocannabinoids.…”

“…There are at least four UHPLC-MS methods available in the literature published using 2020-2023. [79][80][81]83 An Agilent 1290 UHPLC system coupled with a 6530 accurate mass quadrupole time-of-flight mass spectrometer was used for the identification of CBD ( 5), CBDA (6), CBE (20), CBEA (21), and Δ 9 -THC ( 14) in inflorescence extracts. 79…”

“…[79][80][81]83 An Agilent 1290 UHPLC system coupled with a 6530 accurate mass quadrupole time-of-flight mass spectrometer was used for the identification of CBD ( 5), CBDA (6), CBE (20), CBEA (21), and Δ 9 -THC ( 14) in inflorescence extracts. 79…”

“…Since the publication of the review article 2 on the application of HPLC and UPLC (or UHPLC) methods in the analysis of phytocannabinoids covering the period of 2010–2019, several publications have appeared in the literature on this topic 12–185 . All these publications highlight the importance of HPLC and UPLC (or UHPLC) techniques as well as showcase remarkable advancements in sensitivity and versatility associated with these techniques in relation to phytocannabinoid analysis 12 .…”