Botanical samples are often freeze-dried (lyophilized) for use in research studies, and a variety of freeze-dried botanicals are marketed to the public. In both instances, there is an underlying assumption that freeze-drying properly preserves the medicinal qualities of plants, and is superior to other preservation methods. In fact, little systematic research has been done to verify this assumption. A review of the existing research, done primarily by the food and spice industry, indicates that freeze-drying has unanticipated and significant effects on the constituent profiles of medicinal plants that puts into question whether freeze-drying necessarily is the best method to preserve botanical medicines. This research review finds there is insufficient information to conclude that freeze-drying has negative effects on the medicinal qualities of plants. But, because existing research indicates that freeze-drying imperfectly preserves important classes of medicinal compounds (such as volatiles, phenolics and carotenoids), may increase the mutation rate in unicellular organisms and may diminish some medicinal plant actions, researchers and practitioners should carefully consider how the use of freeze-dried material may affect pharmacological and clinical study results.

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