This invention relates to a novel extract from the root of Valerian officinalis that contains high levels of the compound valerenic acid. Valerenic acid ^' exhibits sedative activity in standard animal models. The invention also relates to a method of producing such an extract.

Valerian root has been traditionally used as a herbal medicine with mild tranquillismg and sedative actions. Unlike most traditional herbal medicines there is sufficient evidence of safety and efficacy for Valerian root and preparations derived therefrom to be the subject to an official monograph in the current editions of both the British Pharmacopoeia and the European Pharmacopoeia.

Early scientific opinion held that the essential oil was responsible for the pharmacological actions of Valerian. However the class of epoxy mdoid esters known as valepotriates were discovered in the 1960s and it was subsequently discovered that these compounds exhibited sedative activity. However valepotriates are insoluble in watei and are not present in aqueous or alcoholic extracts of Valeπon root.

The observation that the sedative activity of Valerian root could not be completely accounted for by the presence of the valepotriates stimulated further research and more recently the importance of valerenic acid, a terpenic constituent of the essential oil, has been recognised. Several studies have confirmed the sedative action of this compound in both standard animal models and in enzyme inhibition studies related to key neurochemical pathways. The central role of valerenic acid has been acknowledged by major European manufacturer of pharmacopoeial grade Valerian extract who now standardise their products by reference to the content of valerenic acid or total sesquiterpenes . The official thin layer chromatographic method described in the British Pharmacopoeia for the analysis of Valerian stresses the importance of the presence of both the

valepotπates and valerenic acid. The structure of valerenic acid and the valepotriates is provided below:

A<-e.R-E ^j vc.

In recent years extraction using liquified carbon dioxide has been applied to production of fractions rich in biologically active compounds, particularly terpenoids, from plant based raw materials.

Liquid carbon dioxide has a high selectivity, being able to solubilise low mola mass compounds of moderate polarity whilst leaving behind in the matrix higher molecular weight lipids, waxes and pigments which would otherwise increase the bulk of an extract and dilute the actives content. Liquid carbon dioxide is also superior to non-polar organic solvents m that it is non-flammable, so that the solvent can be safely vented to the atmosphere avoiding waste disposal and recycling costs. The intrinsically non-toxic and highly volatile nature of carbon dioxide avoids any problems of elimination of residual levels of harmful solvents from \ he product.

According to a first aspect of the present invention a method of preparation of an extract containing valerenic acid comprises the step of extraction of Valerian root with liquid carbon dioxide and allowing the carbon dioxide to evaporate from the resultant mixture.

According to a second aspect of the present invention there is provided an extract from Valerian root containing an amount of more than 4%, preferably more than 10% by weight of

valerenic acid, the extract not containing any residual non- hydroxylic solvent.

The resultant residual extract contains a higher percentage of valerenic acid than may be obtained by solvent extraction using aqueous alcoholic mixtures. The extract also exhibits in vivo sedative activity.

A cosolvent may be employed for example a polar hydroxylic solvent such as a C, to C ₄ alcohol, preferably ethanol . An amount of cosolvent of 5 to 20%, preferably 10% by weight may be employed.

Preferred methods involve extraction at a pressure 1400 to 4000 psi (96 to 276 bars) preferably 1500 psi (100 bars) may be employed.

Use of pressure of 1400 to 4000 psi, preferably 1400 to 1500 psi at a temperature of 20 to 40°C is preferred.

Preferred methods in accordance with this invention do not employ a cosolvent as this has been found to give proportions of valerenic acid greater than 10%.

The invention is further described by means of example but not in any limitative sense.

Example

Roughly ground Valerian root was packed into a suitable pressured vessel. A volume of liquid carbon dioxide at the ratio of approximately 10 ml of liquid carbon dioxide per 1 g of herb was allowed to pass through the raw material at a flow rate of approximately 2 ml/min. The liquid carbon dioxide was then collected, the pressure released and carbon dioxide allowed to vent to the atmosphere. Removal of any added cosolvent or residual moisture was completed by drying in a vacuum desiccator. The residual extract in the collection vessel was an oil or semi-solid depending on the exact extraction conditions.

The following range of extraction conditions were employed:

SAMPLE PRESSURE TEMP COSOLVENT % YIELD % VALERENIC ACID

Val 1 1500 psi 25 ° C none 1.1% 10.5%w/w

Val 2 1440 psi 36°C none 1.0% 10.8%

Val 3 1500 psi 25°C 10% 4.5% 5.3% ethanol

Val 4 4000 psi 36% none 1.0% 10.8%

The valerenic acid content was determined by an HPLC method based on that of R Hansel & J Schulz, Deutsche Apotheker Zeitung, 122, 215 - 219 (1982).

Sub-critical liquid C0 ₂ (25°C/1500 psi) liquid C0 ₂ close to the critical temp (36°C/1440 psi) and supercritical C0 ₂ significantly above the critical temperature (36°C/4000 psi) all gave products containing useful proportions of valerenic acid.

The addition of 10% ethanol cosolvent has been found to increase the overall yield of extract but significantly decreased the content of valerenic acid as other more polar compounds were also extracted.