The hot water and 70% ethanol extracts of dried mad-dog skullcap (Scutellaria lateriflora) both bound to the 5-HT(7) receptor, with 87.2 +/- 6.2% and 56.7 +/- 1.3% inhibition of [(3)H]-LSD binding to the receptor at 100 microg/mL, respectively. The on-line analysis of a 70% ethanol extract by HPLC-UV/MS resulted in the identification of five flavones (1-5). Fractionation of the ethanol extract resulted in the isolation of three flavone-glucuronides (6-8) and a flavanone-glucuronide (9), including one new compound, lateriflorin (5,6,-dihydroxy-7-glucuronyloxy-2'-methoxyflavone) (8). The structure of 8 was determined by NMR ((1)H NMR, (13)C NMR, and NOESY experiments) and MS analysis. From the results obtained in the testing of the pure compounds, it is evident that the activity on the 5-HT(7) receptor is at least partly due to the presence of flavonoids. Scutellarin and ikonnikoside I showed the highest inhibition of [(3)H]-LSD binding with IC(50) values of 63.4 and 135.1 microM, respectively.
Recent work has shown that enzymatic degradation and oxidation of cichoric acid and other caffeic derivatives occurs in Echinacea preparations. However, very little is known as to the means of stabilizing these phytopreparations. To stabilize the glycerin extract of Echinacea purpurea, we have evaluated the effects of 3 natural antioxidants (citric acid, malic acid, and hibiscus extract) on the stability of the major caffeic acid derivatives (caftaric acid, caffeic acid, cichoric acid, and 2-O-feruloyl-tartaric acid). Chlorogenic acid, which normally occurs in an ethanol extract of E. purpurea, was not present in the glycerin extract. The caffeic acid derivatives, with the exception of 2-O-feruloyl-tartaric acid, were subject to degradation in the control sample. 2-O-Feruloyl-tartaric acid was stable during the whole testing period. All antioxidant treatments greatly improved the stability of caffeic acid derivatives. Stability was dependent upon the concentration of antioxidant added.
Methods using liquid chromatography with UV detection (LC–UV), thin-layer chromatography (TLC), and digital photomicroscopy were developed to distinguish between the different species of Scutellaria lateriflora L. and its adulterants Teucrium canadense L. and T. chamaedrys L. Chemically, the 70% ethanol extract of S. lateriflora is characterized by the presence of flavonoids—predominantly baicalin, lateriflorin, dihydrobaicalin, and baicalein. The major compounds of the 70% ethanol extract of T. canadense are phenylpropanoids, with verbascoside as the most prominent, and a variable amount of teucrioside. Teucrioside is the major compound in T. chamaedrys, but it is not present in S. lateriflora. The presence of phenylpropane glycosides can therefore be used to distinguish between the S. lateriflora L. and the two Teucrium species by LC–UV and TLC. The abundant strap-shaped tri-chomes on the stem, as well as bristle-like tri-chomes on the leaf, are typically seen microscopically for T. canadense, whereas the waxy cuticle with numerous glandular scales is found in T. chamaedrys. These cell structures were used to determine the adulteration of S. lateriflora crude herb with either of the two Teucrium species.
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