Screening selected medicinal plants for potential anxiolytic activity using an in vivo zebrafish model
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ORIGINAL INVESTIGATION
Screening selected medicinal plants for potential anxiolytic activity using an in vivo zebrafish model Veronica B. Maphanga 1 & Krystyna Skalicka-Woźniak 2 & Barbara Budzynska 3 & Gill M. Enslin 1 & Alvaro M. Viljoen 1,4 Received: 12 July 2019 / Accepted: 13 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Rationale Medicinal plants are used extensively in many countries to treat conditions related to the central nervous system (CNS), and there is renewed interest to explore natural products, which may exhibit CNS activity. Objective In this study, seven plants were selected based on literature reports of their ethnopharmacological use in treating anxiety-related conditions and assayed in a zebrafish model. Methods Crude extracts were prepared with solvents of different polarities, and the maximum tolerated concentration (MTC) of these crude extracts was established. The anxiolytic activity of the crude extracts was determined using 5-day post-fertilization (dpf) zebrafish larvae. General locomotor activity and reverse-thigmotaxis behavior (indicative of anxiolytic activity) were analyzed under continuous illumination and alternating light-dark challenges, which induced anxiety in the zebrafish larvae. Results Of the 28 extracts tested, 13 were toxic according to the MTC values obtained. Larvae were subsequently treated with the 15 non-toxic extracts, at a dose determined in the MTC assay or with 1% DMSO as control. The anxiolytic activity (reversethigmotaxis) was demonstrated by an increase in the percentage time spent by the larvae in the central arena of the well. Of the 15 non-toxic extracts tested, the Sceletium tortuosum water extract exhibited the most promising anxiolytic activity. Conclusions The zebrafish model was effective in studying anxiety-related behavior. Thus, the study confirmed that S. tortuosum mitigates anxiety in zebrafish larvae, a step towards the full in vivo validation of the traditional use of the plant. Keywords Anxiety . Zebrafish model . Anxiolytic activity . Light-dark transitions
Introduction Anxiety is an intense or overwhelming feeling which threatens psychological and physical well-being (Sousa et al. 2015). When the feeling of anxiety continues far beyond the presence of the stimulus and disrupts normal functioning it is defined as an anxiety disorder. The intensity and duration may differ from one person to the other and reach a point where it
* Alvaro M. Viljoen [email protected] 1
Department of Pharmaceutical Sciences, Tshwane University of Technology, Private Bag X680, Pretoria 0001, South Africa
2
Department of Pharmacognosy with Medicinal Plant Unit, Medical University of Lublin, 1 Chodzki Street, 20-093 Lublin, Poland
3
Independent Laboratory of Behavioral Studies, Medical University of Lublin, Jaczewskiego 4, 20-090 Lublin, Poland
4
SAMRC Herbal Drugs Research Unit, Tshwane University of Technology, Pretoria 0001, South Africa
affects normal daily functioning (Koda-Kimble et al. 2012). According to Rom
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