Harvesting Herbs information, tips and advice

Herbal tinctures and extracts are usually made from dried herbs and ethanol-water mixtures. The strength of the ethanol mixture determines how much of the herb's active ingredients end up in the final product. While water-soluble components (., mucilage, tannins) can be extracted in a 25% ethanol solution, other ingredients (., alkaloids, most saponins, essential oils, resins) require higher ethanol concentrations. The most effective concentration for many herbs lies between 40% and 60% ethanol, but researchers have found exceptions. For example, Viburnum prunifolium bark, extracted at 30% ethanol, has five times more spasmolytic action than a 60% extract. In addition to being aware that ethanol concentrations affect the potency of an extract, practitioners need to know that alcohol-water solutions are "selective solvents and do not equally extract everything from the plant that is extractable." Traditional dose recommendations have usually been based on 1:1 extracts, meaning that 1 ml of extract is equivalent to 1 g of the dried herb. When herbalists use more dilute tinctures (preparations that require more than 2 ml to equal 1 g of dried herb), patients need to take more of the preparation to achieve a comparable effect. A Clinical Guide to Blending Liquid Herbs discusses this and other dosage issues for herbal liquids, including how to calculate doses for children.

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In Europe, Japan, and Australia, herbal manufacturers follow the stringent requirements of pharmaceutical good manufacturing practices (GMP). In the US, however, herbal manufacturers need only adhere to GMP designed for food products. Some US companies have chosen to meet almost all of the more demanding pharmaceutical GMP. As part of pharmaceutical GMP, raw herbs that go into the final product undergo several tests for quality and purity. The quality and efficacy of any botanical is affected by growing conditions, harvesting and storage practices, and the manufacturing process itself. These tests help ensure that the plants are correctly identified and not contaminated with pesticide residues, heavy metals, or other unwanted substances. The final product is also tested. Manufacturers check the final product for microbes and pesticide residue. They also measure the amount of active components or other marker compounds to ensure consistent extract strength. Many herbal manufacturers now produce standardized products that have a consistent level of one or more phytochemicals.

In addition to providing readers with a basic understanding of how herbal liquids are made, A Clinical Guide to Blending Liquid Herbs also explains how to combine individual herbs in formulas that treat diverse ailments. Kerry Bone follows the Western herbal system for prescribing and gives readers basic guidelines for combining herbal liquids into an effective formula. The book also includes sample formulas for acute bronchitis, anxiety, chronic fatigue, benign prostate hyperplasia, eczema, depression, osteoarthritis, menopause, and others. User-friendly monographs provide actions, potential indications (rated according to level of evidence), contraindications, precautions, known interactions, side effects, and dosage for over 100 botanicals. Minimum and maximum dosages per day and per week for each herb are provided in an appendix. Appendices also define herbal actions, categorize herbs according to their actions, and provide a quick list of herbs that may be contraindicated during pregnancy.

A Clinical Guide to Blending Liquid Herbs is a worthwhile introduction to the practice of Western herbal medicine. It communicates the challenges of using herbal formulas without becoming bogged down with excessive complexity. For those who want a better understanding of Western herbal medicine, A Clinical Guide to Blending Liquid Herbs provides an excellent start.

review by Jule Klotter