Neurobehavioral evaluation and phytochemical characterization of a series of argentine valerian species

Abstract

Folkloric or galenic preparations of valerian roots and rhizomes have been used as sedatives/anxiolytics and sleep inducers since ancient times. "Valerianas" are plants that naturally grow in our region. Although some of them are used in folk medicine, they lack scientific information. We performed a comparative study of the phytochemical composition and the potential in vivo effects of ethanolic extracts of argentine valerian species: Valeriana carnosa Sm., V. clarionifolia Phil. and V. macrorhiza Poepp. ex DC., from "Patagonia Argentina"; V. ferax (Griseb.) Höck and V. effusa Griseb., from the central part of our country, and V. officinalis (as the reference plant). All these plants were rich in phenolic compounds, evidenced the presence of ligands for the benzodiazepine binding site of the GABA_A receptor and were able to induce sedation as assessed by loss-of-righting reflex assays (500 mg/kg, i.p.). Mice treated with V. macrorhiza, V. carnosa and V. ferax extracts showed reduced exploratory behaviors while V. clarionifolia produced anxiolytic-like activities (500 mg/kg, i.p.) in the Hole board test. Oral administrations (300 mg/kg and 600 mg/kg, p.o.) evidenced sedative effects for V. ferax and anxiolytic-like properties for V. macrorhiza, V. carnosa and V. clarionifolia extracts. Our native valerian species are active on the CNS, validating its folkloric use as anxiolytic/sedative and sleep enhancers.

Keywords: Alternative medicine; Anxiety; Behavioral test; Bioactive plant product; Classifications: behavioral neuroscience; GABAA receptor; Native valerian species; Natural product; Pharmacology; Psychopharmacology; Sedation; Sleep.

Figure 1

Flow sheet of the valerian fractionation scheme.

Figure 2

Protocol of administration procedures. A) Sodium thiopental induced loss of righting reflex assay after intraperitoneal (i.p.) injections; B and C) Hole board and Locomotor activity tests after intraperitoneal (i.p.) and oral administrations (p.o.) administrations, respectively.

Figure 3

Effectiveness of argentine valerian species aqueous 1 extracts on sodium thiopental induced loss of righting reflex assay in mice. Results are expressed as mean ± S.E.M. of A) time of loss of righting reflex, B) latency time to lose righting reflex and C) percentage of mice that lost the righting reflex; after 30 min of an i.p. injection of vehicle (VEH) or the Argentinian valerian species aqueous 1 extracts (500 mg/kg, i.p.) (see Figure 1). The latency to lose righting reflex was measured as the time spent between the sodium thiopental injection (45 mg/kg, i.p.) and the disappearance of the reflex (a cut off of 1800 s was set for those mice that did not lose the reflex) and the time of loss the righting reflex was quantified as the time spent between disappearance and reappearance of righting reflex (cut off of 1800 s) (see Methods). n = number of mice tested. ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001, significantly different from vehicle; Dunn's multiple comparison test after Kruskal-Wallis test (nonparametric ANOVA).

Figure 4

Effect of argentine valerian species aqueous 1 extracts in the holeboard and the locomotor activity tests in mice. Results are expressed as mean ± S.E.M. of A) number of head dips (left scale) and time spent head dipping (s) (left scale), B) number of rearings (left scale), number of groomings (right scale) and number of fecal boli (right scale) registered in a 5 min session, 30 min after the i.p. injections and C) mean ± S.E.M. of the spontaneous locomotor activity counts registered after completing the hole board assay in 5 min sessions and 35 min after the i.p. injections of vehicle (VEH) or 500 mg/kg of the aqueous 1 extract of each valerian. ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001, significantly different from vehicle; Dunnett's Multiple Comparison test after ANOVA. Number of animals per group ranged between 6-8, control animals (VEH) were 31.

Figure 5

Effect of the oral administration of argentine valerian species aqueous 1 extracts in the holeboard and the locomotor activity tests in mice. Results are expressed as mean ± S.E.M. of A) number of head dips (left scale) and time spent head dipping (s) (left scale); B) number of rearings (left scale), number of groomings (right scale) and number of fecal boli (right scale) registered in a 5 min session, 60 min after the oral administrations and C) mean ± S.E.M. of the spontaneous locomotor activity counts; registered after completing the hole board assay in 5 min sessions and 65 min after the oral administration of vehicle (VEH), 300 mg/kg or 600 mg/kg of the aqueous 1 extract of each valerian. ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001, significantly different from vehicle; Dunnett's Multiple Comparison test after ANOVA. Number of animals per group ranged between 6-10, control animals (VEH) were 23.

Figure 6

Capacity of the argentine valerian species extracts to inhibit the binding of [³H]-flunitrazepam to the BDZ-bs of the GABA_A receptor. Results are expressed as mean ± S.E.M. of percentage of binding inhibition of valerian aqueous 1, aqueous 2 and ethylic extracts (1.0 mg/kg) (see Figure 1). Inhibition <30% was considered as no inhibition. Diazepam (10 μM) showed 90 % of binding inhibition.