A toxicological safety assessment of a standardized extract of Sceletium tortuosum (Zembrin®) in rats

A well-characterized standardized hydroethanolic extract of a traditionally recognized mak (mild) variety of Sceletium tortuosum, a South African plant with a long history of traditional ingestion, is marketed under the trade name Zembrin® as an ingredient for use in functional foods and dietary supplements. It is standardized to contain 0.35–0.45% total alkaloids (mesembrenone and mesembrenol ≥60%, and mesembrine <20%). A 14-day repeated oral toxicity study was conducted at 0, 250, 750, 2500, and 5000 mg/kg bw/day. A 90-day subchronic repeated oral toxicity study was conducted at 0, 100, 300, 450, and 600 mg/kg bw/day. Because S. tortuosum has a long history of human use for relieving stress and calming, a functional observation battery, including spontaneous locomotor activity measured using LabMaster ActiMot light-beam frames system, was employed. Several parameters, such as locomotion, rearing behavior, spatial parameters, and turning behavior were investigated in the final week of the study. No mortality or treatment-related adverse effects were observed in male or female Crl:(WI)BR Wistar rats in the 14- or 90-day studies. In the 14- and 90-day studies, the NOAELs were concluded as 5000 and 600 mg/kg bw/d, respectively, the highest dose groups tested.