A UHPLC-(ESI)MS/MS method for the determination of the psychedelic secondary metabolite mescaline in San Pedro (Trichocereus spp.) and its applicability for screening mescaline in other cacti varieties.

Commencements of clinical trials of psychedelic therapies for intractable forms of mental illnesses have drawn increased public attention to plants containing psychedelic substances. Whilst the psychoactive alkaloid mescaline has limited clinical trials, the San Pedro (Trichocereus spp.) cacti from which it is found have a long history of Indigenous medical and spiritual use. Traditional use remains licit in some jurisdictions, as supervised psychedelic dosage is typically regarded as tolerable with reports of only mild intoxications and few persisting negative psychological effects. However, mescaline concentration in ornamental San Pedro is highly variable, introducing risk of unintentional low or high dosage if misdirected for illicit use. This paper reports a validated UHPLC-(ESI)MS/MS method for the convenient and rapid quantification of mescaline in San Pedro, and for screening twelve potentially untested cacti. Preliminary results indicated that there may be higher amounts of mescaline in the chlorenchyma than the parenchyma of San Pedro. While six cacti lacked detectable mescaline, our screening enabled the first quantifications of mescaline in two varieties of Echinopsis subdenudata from 36 μg g⁻¹ to 2.45 mg g⁻¹. Chemotaxonomically, this amount of mescaline in a species from the traditional Echinopsis genus further suggests that the Trichocereus genus is not distinct and may support their contested combination into a single genus. Forensically, the identification of a popular ornamental cactus that was previously not known to contain mescaline demonstrates the need for routine screening of other cacti for the forensic sciences to remain ahead of emerging trends in psychedelic drug use.