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Optimisation of Polysaccharides in
Processed Processed Echinacea purpurea
by D.L. Stuart, R.B.H. Wills and T.MDickeson
Centre for the Advancement of Food Technology and Nutrition, University of Newcastle
November 2004
RIRDC Publication No 04/118 RIRDC Project No UNC-13A
Echinacea is a medicinal herb native the United States that has gained considerable prominence in the western world particularly to stimulate the body immune system to resist viral and other infections
Echinacea has attracted considerable consumer interest in Australia with claims for it to be the most popular medicinal herb on the domestic market. The growing world market for echinacea has also seen keen interest in its cultivation by Australian farmers with annual production rising from less than 1 to 40 tonnes in the last 10 years. Australia is agriculturally well positioned to capture a share of the world market and cropping is now conducted in a wide range of regions across the eastern and southern states. The Australian industry has concentrated on production from Echinacea purpurea with utilisation of both the aerial and root sections of the plant
If Australia is to become successful at exporting and import substitution, it needs to resolve various marketing and quality issues. As consumers become more sophisticated in their requirements for product quality, and world crop supply increases to better match market demand, there will be greater competition in the echinacea market. Countries which have the reputation to consistently supply high quality raw material and processed products will gain 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 echinacea, is the concentration of active constituents that impart a health benefit to the human body. The active constituent groups within echinacea are the caffeoyl phenols, alkylamides and polysaccharides
Wills and Stuart (1999) have previously investigated the alkylamides and caffeoyl phenols in postharvest and processing steps of alcoholic extracts, and have developed a guide outlining optimum conditions for growers and processors to maximise these constituents
Currently, each country uses different constituent groups within echinacea as the quality standard with the United States concentrating on the caffeoyl phenols, and Australia using either the alkylamides or caffeoyl phenols. In Europe, however, the market is dominated by products that have been standardised on the polysaccharide content
In order to increase our knowledge on Australian grown echinacea, as well as determine an additional quality parameter which may open European markets, it is now important to determine the polysaccharide content of echinacea grown in Australia. This study will provide additional information for growers and processors who are interested in preserving the polysaccharide content
The research aim was to develop quality parameters and associated tests to enable growers to harvest and handle E. purpurea to maintain optimum polysaccharide content, and to identify efficient processing techniques that ensure polysaccharides are transferred through to the end products.
To achieve this, the following
aspects were determined:
A study on the polysaccharide
concentration during plant growth revealed a large variation both between
plant sections and sites of growth. While the stem and root had the highest
concentrations, the processors who are interested in the total content
of polysaccharides available per plant would also include the leaf for
the return of polysaccharides. This does not correlate well with the return
of alkylamides and cichoric acid found in previous studies (Wills and Stuart
1999) where the stem was determined as having the least value within the
plant sections. These findings, however, allow for specific plant sections
to be processed to return the optimum levels of specific active constituents
As an example of this, the root and flower would be processed to extract alkylamides/caffeoyl phenols, while the leaf would be processed for polysaccharides/caffeoyl phenols and the stem for the polysaccharides
The northern tablelands returned higher concentrations of polysaccharides per plant within the first season of growth; however, the plant size was smaller than that of plants grown on the coast. This trend reflected previous studies (Stuart and Wills 2000) on alkylamides and caffeoyl phenols, where plants grown at altitude were smaller in the first season of growth, but equivalent in the subsequent season
The postharvest handling has previously been identified as crucial to the development of material suitable for processing. Improving the quality of Australian echinacea through better postharvest handling practices is complicated by the finding that the alkylamides and cichoric acid sometimes respond differently to the various handling operations used, and this is further complicated by the findings of this study into the behaviour of the polysaccharides. Previous results found that echinacea plants were able to withstand a reasonable degree of rough handling, and could be held for prolonged periods as fresh plants at ambient temperature without any significant decrease in level of active constituents. It was recommended therefore, to use this method as a means to decrease drying time and hence overhead costs. These recommendations now require this to be clarified with respect to cichoric acid and alkylamide content only, as this study found that 50% of polysaccharide concentration was lost within the first 10 days of fresh material storage
The study on drying indicates that level of polysaccharides are affected by the drying temperature, however, not in a linear fashion. The findings suggest that optimal drying occurred at 70°C and 40°C with significantly lower returns between these temperatures. This has a high correlation with data obtained for alkylamides in previous studies which also showed a highly significant quadratic relationship between temperature and concentration. It appears therefore, that only the caffeoyl phenols are directly affected by temperature, and further research is required to determine other factors influencing the alkylamides and polysaccharides with respect to temperature
Once echinacea is harvested and dried it is invariably stored for periods during export or before being processed into liquid extracts. A study to determine the stability of dried crushed material was undertaken to determine conditions and timeframes for effective storage without loss of active constituents. This study found that polysaccharide 2 was highly susceptible to storage under these conditions, and this has a huge impact on the postharvest handling of echinacea. Degradation is slightly minimised if material is kept at low humidity (as with the cichoric acid), though loss is still significant (40% in 3 days). Further study is required to determine if this result is replicated in dried whole plant material, and if so, then storage of any plant material prior to processing would be highly disadvantageous to polysaccharide contents. These results indicate therefore that polysaccharides do not correlate with either alkylamides or cichoric acid which could be held for longer than two months without significant loss of concentration
The processing of dried echinacea through extraction of active constituents with aqueous ethanol was found to give highly variable extraction rates with a substantial proportion of polysaccharides being either degraded during processing or not extracted from the starting material. The low maximum extraction levels of 3-4% for polysaccharide 1 and 14-16% for polysaccharide 2 have shown that this method of extraction is highly inefficient. The variability of extraction within the six samples resulting in greater than 15-31% coefficient of variation for individual polysaccharides which indicates further development of processing parameters is required to produce consistent quality. If dry material is to be used for extraction it is required to be freshly dried to ensure a minimum degradation of polysaccharide 2
In contrast to this were extraction yields of 25% for polysaccharide 1 and 70% for polysaccharide 2 in fresh material extraction processing. Of particular interest was the detection of polysaccharide 2 in the aerial section, and the absence of polysaccharide 1 in the root when fresh processing was adopted
This is a major qualitative difference in extracts produced through different techniques, and it could extrapolate to being the difference between therapeutically efficacious and non efficacious extracts
In comparing the fresh material to dry material processing, further investigation on the factors affecting the extraction rate for dry material are required to prove this method of processing is viable against the fresh material method. One area not investigated was the use of alkaline water which should have a greater chance of extracting material found in the hemicellulose compartments of plant cells assumed to be the storage compartments for polysaccharide 1 and 2
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