Chemical profiling and in vitro neuronal assessment of the oneirogenic plant Calea zacatechichi Schltdl.

Background: An increasing number of psychoactive plants, particularly those with long history of use on ritualistic practices, are now being progressively used in a recreational context, with many remaining unregulated [1]. Calea zacatechichi is traditionally used in divination rituals, due to its oneirogenic properties. Yet, considering its psychoactive effects and easiness of purchase, the potential for recreational use is high, with scarce information on its toxicity [2-4]. We aimed to characterize C. zacatechichi aqueous extracts, mimicking those typically consumed, to identify bioactives that underlie the psychoactive or toxic effects, and evaluate their impact upon neuronal function, neurotransmission and radical stress.

Methods: Chemical characterization was attained by HPLC-DAD-ESI/MSn and HPLC-DAD. Impact upon SH-SY5Y and BV-2 cell viability was assessed by the MTT assay and LDH release (up to 1000 µg/mL). Impact on neuromodulation and neuroinflammation was evaluated through acetylcholinesterase and 5-lipoxygenase inhibition, while antiradical properties were approached upon nitric oxide (•NO) and superoxide (O2•-). Statistical comparisons among groups performed by one-way ANOVA followed by Dunnett post hoc test.

Results: From the 28 compounds identified, the majority corresponded to hydroxycinnamic acid derivates, such as 3,5-di-O-caffeoylquinic acid and 4,5-di-O-caffeoylquinic acid, followed by flavonoid derivates, namely quercetin-3-O-rutinoside. Cytotoxic effects were verified at concentrations above 125 µg/mL with LDH leakage starting at 250 µg/mL. Acetylcholinesterase inhibition was recorded at 1000 µg/mL, and a concentration-dependent inhibition of 5-lipoxygenase was found (IC50 = 71.12 µg/mL). Concentration-dependent scavenging effects upon •NO and O2•- were verified at concentrations higher than 62.5 µg/mL.

Conclusions: Even though C. zacatechichi displays apparent antiradical and anti-inflammatory properties, the pronounced cytotoxic effects upon neuronal cells cannot be overlooked, requiring further investigation to elucidate the underlying mechanisms that might be involved.

References: [1] European Monitoring Centre for Drugs and Drug Addiction, European Drug Report 2022:Trends and Developments, Publications Office of the European Union, 2022; [2] Mata R et al. Botany. 2022;100(2):261–74; [3] Leonti M et al. J Ethnopharmacol. 2003;88(2):119–24; [4] Martinez-Mota L et al. J Ethnopharmacol. 2021;265.

Acknowledgements: This work received financial support from PT national funds through the project UIDB/50006/2020 of REQUIMTE/LAQV.