Cannabis-like activity of Zornia latifolia Sm. detected in vitro on rat cortical neurons: major role of the flavone syzalterin

摘要

Zornia latifolia is a plant suspected to possess psychoactive properties and marketed as a marijuana substitute under the name 'maconha brava'. In this study, the effects of fractions obtained from a 2-propanol extract of aerial portions of the plant were determined by multielectrode array (MEA) analyses on cultured networks of rat cortical neurons. Lipophilic (ZLJipo, mainly containing fravonoid agly-cones), and hydrophilic (ZLJiydro, mainly containing fiavonoid glycosides) fractions were initially obtained from the raw extract. ZLJipo significantly inhibited mean firing rate (MFR) and mean bursting rate (MBR) of MEA recordings, while ZLJiydro induced no inhibition. Column chromatography separation of ZLJipo yielded five fractions (ZL1-ZL5), among which ZL1 induced the strongest MFR and MBR inhibition. NMR and HPLC-MS analyses of ZL1 revealed the prevalence of the common flavonoids genistein (1) and apigenin (2) (in about a 1:1 ratio), and the presence of the rare flavone syzalterin (6,8-dimethylapigenin) (3) as a minor compound. Exposures of MEA to apigenin and genistein standards did not induce the MFR and MBR inhibition observed with ZL1, whereas exposure to syzalterin standard or to a 1:9 mixture syzalterin-genistein induced effects similar to ZL1. These inhibitory effects were comparable to that observed with high-THC hashish, possibly accounting for the plant psychoactive properties. Data indicate that Z. latifolia, currently marketed as a free herbal product, should be subjected to measures of control. In addition, syzalterin showed distinctive pharmacological properties, opening the way to its possible exploitation as a neuroactive drug.