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Rural Industries Research & Development Corporation
Production of High Quality Australian Valerian Products
By R.B.H. Wills and D.ShohetSeptember 2003
RIRDC Publication No 03/081 RIRDC Project No UNC-11A
The quality issues will be driven by consumers who will become more demanding in their requirements for product quality, and as world crop supply increases to better match market demand there will be greater competition in the valerian market. Countries which have the reputation to consistently supply high quality raw material and processed products will undoubtedly have preferential access to the higher price market segment, thus maximising the economic return from the crop.
The over-riding determinant of quality in all medicinal herbs, including valerian, is the concentration of active constituents that impart a health benefit to consumers. While there is still some debate on the relative effectiveness of various classes of compounds, it is widely accepted that the valerenic acids are important active constituents in valerian and there is substantial industry interest in increasing the level of valerenic acids in traded products. The research studies described in this report used the total valerenic acids, that is combined level of valerenic acid, acetoxyvalerenic acid and hydroxyvalerenic acid (stored roots only), as the marker of valerian root quality. A major logistical problem for growers is difficulties in efficiently washing valerian roots and is often cited as a significant barrier to continuing with the crop.
The overall aim of the project was to assist the Australian
industry, that is, growers, traders and processors, to improve the quality
of Australian grown valerian. The research objectives focused on determining:
Efficient and reliable quantitative analytical
methods for the analysis of valerenic acids, valepotriates and baldrinals
in valerian were developed using high performance liquid chromatography
(HPLC). The measure of quality in the studies was based on the industry
stated preference for valerenic acids although the levels of valepotriates,
baldrinals and essential oil were also determined in all studies.
The level of valerenic acids in commercially available roots from plants of the Anthos cultivar, the current preferred industry cultivar, was found to average about 3 mg/g dry weight. While there is a number of suggested standards for the concentration of valerenic acids, based on the recommendation of 3 mg/g by Bos et al. (1998) for high quality valerian, the Australian industry would seem to be already a high quality producer of valerian.
However, there seems to be an opportunity for the Australian industry to raise the quality of valerian over time. This conclusion was reached from a study that evaluated valerian seed obtained from 25 sources of valerian with six types from Australian growers, and four from North American and 15 from European seed companies and botanical gardens grown at three sites in New South Wales with different climatic features. It was found that five sources seed consistently generated valerenic acid levels >4 mg/g. It was noteworthy that three of the five lines were obtained from Australian growers in New South Wales, Tasmanian and Victoria with the other two lines from France and Russia. The Russian line in particular appears promising as the high valerenic acids content is matched by a larger than normal root size. These plant sources are worthy of further growing trials to evaluate their agronomic performance under a wider range of environmental conditions and to test the consistency the elevated valerenic acids levels. The identified plant material may ultimately fail subsequent trials to be commercially acceptable but the study has demonstrated the potential for the Australian industry to increase the quality of its valerian. While processors prefer source roots with a high concentration of valerenic acids, establishment of a price return based on quality would seem to be a pre-requisite to encourage grower participation in quality enhancement.
A study was conducted of the change in the content of the total valerenic acids at five development stages of 1-year old Anthos plants in their subsequent seasonal growth cycle.
This was undertaken primarily to determine whether the current practice of harvesting plants at the senescence stage was optimal in terms of active constituents. The concentration valerenic acids in roots was found to rise sharply from the plant dormant stage to a peak in the spring vegetative growth stage and then fall substantially through to the senescence stage.
However, while the maximum concentration of valerenic acids was in spring, the overall yield of valerenic acids per root increased with root age. This was due to continuous linear rate growth of roots throughout the seasonal growth cycle. It might be expected that 3-year old plants would be larger still although this was not determined. While manufacturers may prefer to receive roots with maximal concentration of active constituents, it may be more desirable to maximise the overall yield of active constituents in Anthos plants by continuing to have growers harvest roots at the senescence stage.
Postharvest handling practices are a major operational issue for growers with the difficulty removing soil from around valerian roots cited by various growers as a major problem. An evaluation of cutting and soaking of roots showed no overall benefit in reducing the time taken to remove soil from around roots. While there was a reduction in washing time following the quartering of roots and removing rootlets from the crown there was no beneficial effect of soaking and when the time taken to cut the plants was added to the washing time, there was no overall time saving. There was, however, a greatly reduced drying time of cut roots in a hot air drier with rootlets drying in 20-30% of the time taken by whole roots. It would therefore seem that a more efficient use of driers would be obtained by routinely separating rootlets from the crown and drying each plant part in a separate batch.
further advantage is that there was a greater retention of valerenic acids in dried rootlets and crown that had been separated before drying. Rootlets tended to have a higher concentration of valerenic acids than the crown which could allow their segregation and sale as a higher quality product. The feasibility of separately drying rootlets and crown was further enhanced by the storage for 10 days of whole roots closely stacked in a wire basket at ambient temperature and humidity. There was no significant change in the level of any active constituent but there was a substantial loss of moisture which would further reduce the time roots needed to be held in a drier. This indicates that roots could be separated into rootlets and crown and stored separately without loss of quality until a drier load of material had been accumulated.
The drying temperature was, as expected, directly related to the drying time with a 12-fold decrease over the temperature range of 15°-70°C. There was, however, a substantial decrease in the level of valerenic acids at higher drying temperatures with the most marked change occurring between 40° and 50°C. It would thus seem that the temperature of a hot air drier should not be maintained above 40°C. The heat pump drier with its use of reduced humidity air was found to give a 25% shorter drying time at 38°C than a hot air drier operated at the same temperature with no adverse effect on any active constituent. The benefit of faster drying and hence greater throughput would need to be considered against the higher purchase cost but lower energy usage of a heat pump drier.
Current general storage recommendations for dried valerian are in a closed container protected from light, air and moisture. This study found that the valerenic acids were quite unstable during storage with the rate of loss increasing as the temperature increased and the humidity decreased with >50% loss in root held at 30°C in air of 10% RH over 6 months.
Exposure to light further accelerated the loss of valerenic acids. Thus, retention of valerenic acids is favoured by storage at low temperature in the dark. It would seem to be also favoured by retention of a high humidity atmosphere but no explanation can be offered as to the mechanism resulting in such an effect. A preliminary evaluation into the mode of action of loss suggested that both enzymic activity and atmospheric oxidation were involved in the degradation of active constituents. However, there was also substantial loss of valerenic acids during blanching suggesting that use of water blanching was not a commercial option. The studies were only on ground valerian and thus only have direct application for processors.
However, there is no reason to doubt that the findings would apply to dried, non-ground root, although the rate of degradation may be at a slower rate.
The extraction of dried valerian with solutions of ethanol in water was found to give highly variable extraction of active constituents with different ethanol:water mixtures. The common commercial use of aqueous ethanol in the ratio range of 60:40 to 70:30 ethanol:water is in large part supported by this study as an efficient use of ethanol although some increase in extraction was obtained with higher ethanol concentrations. The valerenic acids were quite stable in ethanolic solution even when stored at ambient temperature and should provide flexibility for industry to efficiently manage either long term storage or holding for further processing while maintaining product quality.
Extraction by percolation was found to be more efficient than maceration with about 15% more valerenic acids obtained at the same ethanol concentration. The rate of solvent flow during percolation did not appear to affect extraction efficiency, hence a faster flow rate with considerable time saving could be used. Furthermore, valerenic acids were readily extracted with percolation in 80% ethanol achieving about 95% extraction of valerenic acids using a relatively low solvent:valerian ratio of 2:1. At 60% ethanol, a ratio of about 3:1 was required to achieve a similar rate of extraction or the extraction rate falls to 85% which could still be acceptable. Maceration also showed a similar early extraction of most of the valerenic acids with little increase in extraction using times greater than 4 hr.
Valerenic acids were also readily extracted using supercritical fluid extraction (SFE) with CO2 where >90% of extraction occurred in 10 min and with use of relatively mild conditions of 15 MPa and 40°C. The addition of 5% ethanol extracted greater amounts of the valerenic acids and the efficiency was comparable to extraction by percolation. The advantage of SFE is elimination of the need to handle large volumes of solvents and its more benign environmental, health and safety features. The technique is worthy of further investigation although it may be too costly at this stage although SFE has been applied commercially to various foods.
A survey of 55 commercial manufactured products showed considerable variation in concentration of valerenic acids from <0.01 to 6.32 mg/g or ml of product with about 20% of products containing >2 mg/g or ml while 50% contained <1mg/g which included 16% <0.1 mg/g. Powder capsules contained the highest concentration (2.5 mg/g), the tablets, teas and soft gel capsules had about 1 mg/g while liquids contained 0.5 mg/ml. The minority of products with a stated label content of valerenic acids had much higher valerenic acid contents than non-standardised products and while the stated and actual levels were reasonably well correlated, there was a 10-15% lower level in products than the label claim.
The calculated values of valerenic acids in products in relation to the amount of added valerian ranged from <0.01 to 2 mg/g root which is similar to the range reported in various European studies.
There was a large variation in recommended daily doses on product labels. It would seem that this would be confusing to consumers. It was noted that for about 50% of products the recommended dose was <2 g/day which is lower than the European range of recommended dosage. It is suggested that labelling of products with valerenic acids content and a more uniform recommended dosage would give consumers greater confidence in the continued purchase of valerian products.
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