Effect of storage on plants.
Amongst herbalists there is often debate about the most therapeutic forms of dosing our herbs. Tinctures, infusions, decoctions, glycetracts and encapsulated dried herbs are all commonly used, but efficacy may vary between the method of extraction and between herbs, as different constituents require different methods of preparation to exert their maximal effects.
The current study examined the effects of storage and preparation on the antioxidant capacity of Mentha pulegium (pennyroyal), Mentha spicata (spearmint), Aloysia citrodora (lemon verbena) and Foeniculum vulgare (fennel). These herbs are commonly used as tisanes and decoctions throughout Europe and the Middle East. Their antioxidant properties are valuable for health prophylaxis and for the management of a number of diseases. In this study phenolics and flavonoids were the main free radical scavenging constituents identified for all of the plants.
The aerial parts of the four plants were gathered in summer, taking into account local consumer's criteria and optimal growth stage preferences for preparing herbal beverages. The respective samples were then prepared either fresh immediately after being collected, or after being shade dried and stored in a dark, dry, room temperature place for 30, 60 or 120 days.
Infusions and decoctions were prepared according to folk recipes with ratios of half a litre of water to a handful of fresh plant material (or dried equivalent). For each infusion 500 mL boiling water was added to the sample and left to stand at room temperature for 5 minutes. It was then filtered, frozen, lyophilised and redissolved in water at a concentration of 2.5 mg/mL. Decoctions were prepared by adding the sample to 500 mL of distilled water and then heating until boiling. This was left to stand at boiling temperature for 5 minutes, at room temperature for a further 5 minutes and then filtered, frozen, lyophilised and redissolved in water at a concentration of 2.5 mg/mL.
Of the herbs tested, spearmint displayed the strongest antioxidant properties, followed by pennyroyal and lemon verbena with fennel displaying the lowest. Infusions gave better results than decoctions for all of the herbs and storage periods studied. This may be due to the thermal shock involved in that procedure. The authors also note that infusions and decoctions seem to have higher antioxidant properties than ethanolic or methanolic extractions (based on data from previous studies). However overall the storage time had a higher influence than the preparation method on antioxidant capacity. The best results were obtained (in the following order) from:
* Infusion at 30 days
* Infusion at 60 days
* Fresh infusion
* Decoction 30 days
* Decoction 60 days
* Fresh decoction
* Infusion 120 days
* Decoction 120 days
This study provided interesting results for those herbalists inclined to recommend tisanes as a part of their medicinal practice.
Tessa Finney-Brown MNHAA
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|Publication:||Australian Journal of Medical Herbalism|
|Date:||Jun 22, 2011|
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