Valeriana officinalis L. (Valerianaceae), commonly known as valerian, is probably one of the most popular medicinal herbs used throughout human history. The reputation of this plant in modern rational phytotherapy is mainly due to its pharmacological properties as a mild sedative, and for treating mild nervous tension and temporary sleeping problems. The active compounds for these effects, however, remain a matter of great controversy (Bisset and Wichtl, 2001). The interest in studying V. officinalis as an inhibitor of NF-κB emerged from the knowledge of its traditional use as an anti-inflammatory remedy in Europe and the use of related species in Central America/Mexico for similar purposes (Cáceres, 1999; Mayer, 2003). Therefore, the aim of the present study was to investigate the effects of an EtOAc extract of V. officinalis on neurophysiological pathologies linked with the NF-κB pathway (Bremner and Heinrich, 2005) and through bioassayguided fractionation to isolate fractions and compounds from an active EtOAc extract of V. officinalis using the IL-6/luciferase assay as a lead. In particular, the study focused on the potential protective effect of the EtOAc extract against excitotoxicity, which is known to contribute to the pathogenesis of stroke and neurodegenerative diseases.
Plant material. Rootstock of V. officinalis was commercially supplied by Potter’s Herbal Medicines© (Leyland Mill Lane Wigan, Lancs WN1 2SB, UK). Powdered plant material (400 g) was extracted by cold maceration with ethyl acetate (2 L) at room temperature. The solvent was removed under vacuum and dried with a rotavapor to give a total crude extract of 9 g which was stored at −20 °C. Compound 1 (6 mg), acetylvalerenolic acid (acetoxyvalerenic acid), was isolated by two different chromatographic techniques: (a) vacuum liquid chromatography on silica gel column (5 g of crude extract) using a hexane–EtOAc gradient elution system (10:0, 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, 1:9, 0:10; 100 mL each), and purified by preparative TLC [hexane–EtOAc 7:3, 1:2; Rf = 0.59 (hexane–EtOAc 1:2)]; and (b) preparative HPLC (gradient, 100% H2O–100% ACN; retention time 31 min). Compound 2 (9 mg), valerenal, was isolated by a solid phase extraction gradient system, using hexane–CHCl3 as eluent (increments of 5% starting 10:0) and preparative TLC [hexane– CHCl3 3:2; Rf = 0.65 (hexane–CHCl3 1:1)]. Compound 3 (6 mg), valerenic acid, was isolated by Sephadex LH20 (4 g of crude extract, EtOH as mobile phase) and preparative TLC [hexane–EtOAc 7:3; Rf = 0.52 (hexane– EtOAc 1:2)]. Characterization of compounds was achieved using 1 H and 13C NMR spectra in CDCl3 and comparing the data obtained with those from previously published spectral data (Bos et al., 1986; Dharmaratne et al., 2002). Copies of the original spectra can be obtained from the corresponding author upon request.
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