GB2317613A - A method for producing an extract from paeonia containing high levels of paeoniflorin - Google Patents

Abstract

The method of preparation of an extract containing paeoniflorin comprising the steps of: extraction of Paeonia lactiflora with a mixture of liquid carbon dioxide and propanol and allowing the carbon dioxide to evaporate from the resultant mixture.

Description

A METHOD FOR PRODUCING AN EXTRACT FROM PAEONIA CONTAINING HIGH LEVELS OF PAEONIFLORIN This invention relates to the production of a novel extract from Paeonia lactiflora which contains high levels of the known anti-inflammatory active paeoniflorin. The invention also relates to a method of producing such an extract.

Paeonia lactiflora, particularly the root, has been used for many centuries in traditional Chinese medicine as a component of treatments for diseases with an inflammatory component. Recently pharmacological research has led to the isolation of a monoterpene glycoside known as paeoniflorin.

This is thought to be the most important anti-inflammatory active in the herb and pure samples of this compound have been shown in standard animal models to exhibit strong activity.

The structure of paeoniflorin is given below:

The aglycone portion of paeoniflorin has a complex cage structure and is difficult to synthesise. Small amounts of the pure compound are normally isolated from the plant material by aqueous alcoholic extraction followed by fractionation.

In recent years the technique of liquid carbon dioxide extraction has been applied to the isolation of potential pharmaceutical actives from plant materials. Liquid carbon dioxide has the advantage over water/alcohol mixtures that a large amount of energy is not required to free the extract from the solvent after extraction as the liquid carbon dioxide vaporises completely when the pressure is returned to normal atmospheric pressure. Liquid caroon dioxide also tends to be more selective than water/alcohol mixtures in that it does not solubilise high molecular weight or very polar compounds which can often increase the bulk on an extract thus diluting the active content. Liquid carbon dioxide has the advantage over organic solvents that there is no residual solvent which must be removed before a product is acceptable for human use. The gas is harmless under ambient conditions and may be vented to the atmosphere thus avoiding any waste solvent disposal problems.

A limitation of liquid carbon dioxide is that it can only solubilise relatively non-polar compounds, but this can be overcome by the addition of small amounts of more polar cosolvents which increase the versatility of the extraction method.

JP-A-6200496 discloses use of supercritical carbon dioxide together with methanol, ethanol or acetone as a cosolvent.

According to the present invention a method of preparation of an extract containing paeoniflorin comprises the steps of extraction of Paeonia lactiflora with a solvent mixture of liquid carbon dioxide and propanol and allowing carbon dioxide to evapor-ate from the resultant mixture.

Use of propanol has an advantage in comparison to other solvents such as chloroform or methanol in that it is nontoxic, avoiding any necessity fDr complete removal of the cosolvent from the product. Alternative solvents such as ethanol or acetone are more flammable and pose a hazard in manufacture. The method of the present invention provides an extract with a high paeoniflorin content.

The preferred cosolvent is isopropanol in an amount of 5 to 20%, preferably 10% by weight.

Preferred methods involve extraction at a pressure of 1500 to 4500 psi (100 to 310 bars) preferably 1500 psi (100 bar) The invention is further described by means of example but not in any limitative sense.

ExamPle Roughly ground root material from Paeonia lactiflora was packed into a suitable pressure vessel and a volume of liquid carbon dioxide at the ratio of approximately 7.5 ml per 1 g of ground herb was allowed to pass through the raw material at a rate of approximately 1 ml/min. The liquid carbon dioxide is then collected. The pressure was released and the carbon dioxide was allowed to vent to the atmosphere. The remaining extract in the collection vessel was an oil or semi-solid depending on the extraction conditions.

The following range of extraction conditions were employed:

SAMPLE PRESSURE TEMP | COSOLVENT | % YIELD | CONTENT 1 (w/w) Pae 1 1500 psi 26 C None 0.4 0.8% Pae 2 1500 psi 26 C 10% IPA 2.8% 9.2% Pae 3 4500 psi 40 C None 0% N/A Pae 4 4500 psi 40 C 10% IPA 1.6% 7.7% CONTENT 1 is the paeoniflorin content of the sample determined by HPLC. Conditions of 1500 psi/26"C are equivalent to subcritical liquid carbon dioxide and 4500 psi/40 C are equivalent to supercritical liquid carbon dioxide.

The paeoniflorin content of the sample was determined by HPLC.

The optimum conditions for both overall yield of extract and paeoniflorin content were provided by subcritical liquid carbon dioxide combined with 10% Fropanol cosolvent.

Subcritical conditions would also be preferred over the supercritical conditions previously disclosed as energy costs are lower and less robust and complex equipment is required.

Claims (7)

1. The method of preparation of an extract containing paeoniflorin comprising the steps of: extraction of Paeonia lactiflora with a mixture of liquid carbon dioxide and propanol and allowing the carbon dioxide to evaporate from the resultant mixture.

2. A method as claimed in claim 1, wherein the solvent is isopropanol.

3. A method as claimed in claim 2, wherein the solvent mixture comprises 5 to 20% by weight.

4. A method as claimed in claim 3, wherein the amount of isopropanol is 10% by weight.

5. A method as claimed in any preceding claim, wherein the extraction is carried out at a pressure of 1500 to 4500 psi.

6. A method as claimed in claim 5, wherein the extraction is carried out at a pressure of 1500 psi.

7. A method of preparation of an extract containing paeoniflorin substantially as hereinbefore described.