**3. Conclusions**

**2.4. High-performance liquid chromatographic analysis of licorice phenolics**

70 Biological Activities and Action Mechanisms of Licorice Ingredients

into the following three types depending on several major constituents [21].

which were also present in some of the materials from Chinese markets.

**Figure 9.** Characteristic phenolics observed in the extracts from *G. uralensis*.

**Figure 10.** Characteristic phenolics observed in the extracts from *G. glabra*.

HPLC analysis revealed the presence of characteristic constituents depending on the original plant species. The *Japanese Pharmacopoeia* indicates that licorice used as a medicinal material must be derived from the origins of *G. uralensis* and *G. glabra*. Our analytical investigation on licorice materials from various sources indicated that the HPLC profiles could be separated

Type A: Using HPLC analysis, the standard materials established as *G. uralensis* in China were found to contain three relevant compounds: glycycoumarin, licopyranocoumarin, and licocoumarone (**Figure 9**). Conversely, HPLC analysis of the standard materials of *G. glabra* and *G. inflata* did not indicate the presence of these three compounds. All of the materials obtained from Japanese markets contained glycycoumarin, licopyranocoumarin, and licocoumarone,

Type B: Analogously, the standard materials from *G. glabra* identified in China contained glabridin and glabrene (**Figure 10**), whereas these two were not observed for the standard materials from *G. uralensis* and *G. inflata*. The materials from Russia and Afghanistan revealed these two constituents, which were absent in the Japanese and Chinese market products.

Type C: The standard materials from *G. inflata* included licochalcones A and B (**Figure 11**),

These results suggest that glycycoumarin, licopyranocoumarin, and licocoumarone could be used as markers for *G. uralensis* (Type A). At the same time, glabridin and glabrene could be used as markers for *G. glabra* (Type B), and licochalcones A and B could be used as markers for *G. inflata* (Type C). However, licochalcone B was later isolated from a Japanese market sample.

and several materials from Chinese markets also showed analogous HPLC patterns.

Licorice extracts contain various types of flavonoids and related compounds. In addition to the protein-binding properties and antioxidant effects, we examined their antiviral and antibacterial properties. The findings, especially those found in the studies of antibacterial phenolics in licorice using MRSA and VRE, emphasize the importance of lipophilic prenyl groups together with phenolic hydroxyl groups, in addition to the flexibility of their structural skeletons. Additional studies on these plant constituents are currently in progress [45]. Because naturally occurring polyphenols have structural limitations based on the biogenetic capability of plants, further studies with the aid of synthetic chemistry are expected for clarifying quantitative structure-activity relationship concerning their pharmacological effects and for optimizing candidates of new drugs.
