Comparison of the relaxant activities of the roots of three Glycyrrhiza species and location of the active ingredients within the roots

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The relaxant effects of the roots of three species of Glycyrrhiza (G. uralensis, G. glabra and G. inflata) on carbachol-induced contractions in mouse jejunum were examined. The G. inflata (EC50: 93 ± 25 μg/ml) and G. uralensis roots (EC50 of 4-year-old cultivated roots: 134 ± 21 μg/ml) had potent relaxant effects; however, G. glabra had only weak activity (EC50: 250 μg/ml or more) because it did not contain the potent relaxants glycycoumarin (GC) and licochalcone A (LA). Cultivated G. uralensis roots, obtained during our previously reported cultivation studies in eastern Inner Mongolia, China, showed similar relaxant effects to commercial Glycyrrhizae Radices prepared from wild G. uralensis roots. The relaxant effects of commercially available cultivated G. uralensis roots were also comparable to those of three commercial Glycyrrhizae Radices. Our results suggest that cultivated G. uralensis roots could be used as an acceptable source of Glycyrrhizae Radix, which would conform to the Japanese Pharmacopoeia XV. The relaxant effects of the outer periderm (cork, cortex and part of the phloem) of Glycyrrhiza roots were stronger than those of the inner residual tissues (phloem, xylem and xylem rays), probably because the active ingredients, GC and LA, were abundantly present in the outer periderm of G. uralensis and G. inflata roots, respectively.
和漢医薬学会の論文