Herbal medicines prepared by traditional and contemporary methods – a comparative study

Abstract

The traditional use of herbal medicines is often cited as justification for their efficacy and safety. This argument, however, fails to take into account the potential differences between preparations made using traditional aqueous extraction techniques compared with more contemporary methods using ethanol. The aim was to compare the amount of specific active constituents found in a typical daily dose of extracts prepared using different extraction methods and different herb-to-extract ratios. Three widely used medicinal plants, Matricaria recutita, Glycyrrhiza uralensis and Withania somnifera were prepared in a variety of ways reflecting different traditional methods (infusions and decoctions) and more contemporary methods (hydroethanolic macerations and percolations). The resulting extracts were analysed using HPLC and/or GC-MS. Specific constituents (3–6 for each species) were quantified using calibration curves of pure reference compounds to enable comparisons between the different extraction methods and herb-to-extract ratios. Traditional, aqueous extraction methods were less efficient at extracting the constituents under investigation. However, because traditionally prepared infusions and decoctions are made from a greater amount of raw material, the total amount of the examined constituents delivered per daily dose was higher for these methods. Further, the concentration of constituents in macerations and percolations did not show a linear relationship with the herb-to-extract ratio. This may be due to saturation effects. Traditional aqueous extracts such as infusions and decoctions are not necessarily less potent than ethanol based extracts, although practitioners often assume so. These findings have implications for the safe and efficacious prescribing of herbal medicines.