Untitled

Abstract

Introduction !Various stress conditions in daily life influence human health and may cause physical disorders, such as insomnia [1] and anxiety [2]. Benzodiazepines are widely used as sedative drugs but are associated with problematic side effects, including oversedation [3] or ataxia [4]. Therefore, as one of the complementary and alternative medicinal therapies, aromatherapy has recently attracted much attention for its ability to induce relaxation and to ameliorate stress. Spikenard, the dried underground part of Nardostachys chinensis Batalin, is a member of the family Valerianaceae found growing from Himalayan regions to southwest China. In traditional Chinese medicine, spikenard has been used as a gastrointestinal antispasmodic [5] and a traditional herbal tranquilizer [6]. Spikenard is also an essential ingredient in scented sachets used to improve insomnia.Our research focused on the characteristic fragrance of spikenard, the expression of the sedative effect by fragrance inhalation, and the identification of active ingredients. In our previous study, we investigated the sedative effect of the spikenard hexane extract by inhalation administration in mice. We identified four hydrocarbon sesquiterpenoids from the spikenard hexane extract as active compounds [7,8] and also revealed that its sedative effect due to administration by inhalation was expressed via olfactory stimulation and pulmonary absorption [9]. While preparing the spikenard essential oil to identify other volatile compounds by GC-MS analysis, we detected several high intensity peaks in addition to the peaks for hydrocarbon sesquiterpenoids mentioned above (l " Fig. 1). The aim of the present study was to identify those compounds and to determine whether they contribute to the sedative effect of spikenard. The sedative activities of isoAbstract ! Spikenard, the dried roots of Nardostachys chinensis, contains sesquiterpenoids and is widely used as an herbal tranquilizer. We previously demonstrated that spikenard vapor showed a sedative effect when administered by inhalation, and we identified hydrocarbon sesquiterpenoids as active components. Here we investigated the other components that contribute to the effects of spikenard. Six oxygenated sesquiterpenoids, including aristolane-and guaiane-types, were isolated from an acetone extract of spikenard. We evaluated the sedative activities of these oxygenated compounds using an inhalation administration method in a caffeine-treated excitatory mouse model. We identified aristolen-1(10)-en-9-ol and patchouli alcohol as highly effective sedative components. These compounds inhibited locomotion in mice by approximately 60% at a dose of 300 µg/cage. In addition, aristolen-1(10)-en-9-ol prolonged pentobarbital-induced sleep to the same extent as 1 mg/kg diazepam. This effect completely disappeared with the administration of the GABA A -benzodiazepine receptor antagonist flumazenil (3 mg/kg), suggesting that the sedative effect of aristolen-1(10)-en-9-ol is expressed via the GABAergic system. Furthermor...