Cannabidiolic acid (CBDA) and trans-Δ9-tetrahydrocannabinolic acid (trans-Δ9-THCA) are known to be the major phytocannabinoids in Cannabis sativa L., along with their decarboxylated derivatives cannabidiol (CBD) and trans-Δ9-tetrahydrocannabinol (trans-Δ9-THC). The cis isomer of Δ9-THC has been recently identified, characterized and quantified in several Cannabis sativa varieties, which had been heated (decarboxylated) before the analysis. Since decarboxylation alters the original phytocannabinoids composition of the plant, this work reports the identification and characterization of the carboxylated precursor cis-Δ9-THCA. The compound was also synthesized and used as analytical standard for the development and validation of a liquid chromatography coupled to high resolution mass spectrometry-based method for its quantification in ten Cannabis sativa L. samples from different chemotypes. The highest concentrations of cis-Δ9-THCA were found in CBD-rich varieties, lower levels were observed in cannabigerol (CBG)-rich varieties (chemotype IV) and in those varieties with a balanced level of both CBD and THC (chemotype III), while its levels were not detectable in cannabichromene (CBC)-rich varieties (chemotype VI). The presence of the cis isomer of THC and THCA raises the question on whether to include or not this species in the calculation of the total amount of THC to classify a cannabis variety as a drug-type or a fiber-type (hemp).

Centre of the Region Haná for Biotechnological and Agricultural Research Department of Genetic Resources for Vegetables Medicinal and Special Plants Crop Research Institute Šlechtitelů 29 78371 Olomouc Czech Republic; Department of Biochemistry Faculty of Science Palacký University Šlechtitelů 27 78371 Olomouc Czech Republic

Clinical and Experimental Medicine PhD Program University of Modena and Reggio Emilia 41125 Modena Italy; Department of Biomedical Metabolic and Neural Sciences University of Modena and Reggio Emilia 41125 Modena Italy

CREA Research Center for Cereal and Industrial Crops Via di Corticella 133 40128 Bologna Italy

Department of Biomedical Metabolic and Neural Sciences University of Modena and Reggio Emilia 41125 Modena Italy

Department of Chemistry Sapienza University of Rome Piazzale Aldo Moro 5 00185 Rome Italy

Department of Life Sciences University of Modena and Reggio Emilia Via Campi 103 41125 Modena Italy

Institute of Nanotechnology CNR NANOTEC Campus Ecotekne Via Monteroni 73100 Lecce Italy

Institute of Nanotechnology CNR NANOTEC Campus Ecotekne Via Monteroni 73100 Lecce Italy; Department of Chemistry Sapienza University of Rome Piazzale Aldo Moro 5 00185 Rome Italy

Institute of Nanotechnology CNR NANOTEC Campus Ecotekne Via Monteroni 73100 Lecce Italy; Department of Life Sciences University of Modena and Reggio Emilia Via Campi 103 41125 Modena Italy

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