products for one class of constituents typically reduce or exclude others, with the exception of polysaccharides and glycoproteins, which are water soluble.

In Vitro Pharmacological Characterization of Echinacea Constituents

The most common constituents found in standardized extracts include polyunsaturated alkylamides or caffeic acid derivatives such as cichoric, chlorogenic, and caftartic acids. These compounds have been shown to inhibit cyclooxygenase and 5-lipoxygenase, key enzymes associated with inflammation via the production of prostaglandins and leukotrienes (Clifford et al., 2002; Muller-Jakic et al., 1994). Cyclooxygenase inhibition is the mechanism of action of nonsteroidal antiinflamma-tory drugs, such as indomethacin and acetaminophen, which are well known and tolerated to reduce fever and pain associated with colds and flu. The inhibition of cyclooxygenases could explain some of the benefits associated with Echinacea; however, the potency of individual Echinacea alkyla-mides is only fractional at concentrations of 100 mg/ml (Clifford et al., 2002). The phenolic caffeic acid derivatives may be more potent for this activity based on in vitro cellular assays measuring prostaglandin production from stimulated macrophage cells (Rininger et al., 2000). Phenolic standardized extract did inhibit prostaglandin production by approximately 40% at concentrations of 20 mg/ml (Rininger et al., 2000). In contrast, indomethacin, a commonly used pain reliever and fever reducer, yielded approximately 90% inhibition of prostaglandin production at concentrations 200-fold lower than the Echinacea concentrations tested.

Phenolic constituents and extracts have also been shown to possess potent free-radical scavenging activity, an antioxidant property that has been linked to improving immune function (Kim et al., 1997; Rininger et al., 2000). Table 12.1 shows the results of direct free-radical scavenging activity of various forms of Echinacea and extract constituents caffeic acid and chlorogenic acid. Interestingly, there is a wide range in potency among standardized preparations, which brings us to the question of standardization test methodology. E. purpurea herb preparations showed relatively little potency in this free-radical scavenging assay. In addition, cichoric acid has been described to

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