Yukiyoshi Tamura

Antioxidative and superoxide scavenging activities of retrochalcones in Glycyrrhiza inflata

Licochalcone A, B, C, D and echinatin, retrochalcones isolated from the roots of Glycyrrhiza inflata (licorice), along with an ordinary chalcone isoliquiritigenin, were assessed for their inhibitory activities on lipid peroxidation in various systems and radical scavenging activity. Among those tested, licochalcones B and D strongly inhibited superoxide anion production in the xanthine/xanthine oxidase system. These two compounds also showed potent scavenging activity on DPPH radical. Microsomal lipid peroxidation induced by Fe(III)-ADP/NAPDH was inhibited almost completely by 3 micrograms/ml of licochalcones B and D. Mitochondrial lipid peroxidation induced by Fe(III)-ADP/NADH was more sensitive to these retrochalcones; almost complete inhibition was observed at 10 micrograms/ml of all retrochalcones tested. Licochalcones B and D scavenged superoxide anion in microsome. Furthermore, these retrochalcones protected red cells against oxidative hemolysis. These phenolic compounds were shown to be effective to protect biological systems against various oxidative stresses.

Mode of antibacterial action of retrochalcones from Glycyrrhiza inflata

Licochalcone A-D and echinatin, retrochalcones isolated from the roots of Glycyrrhiza inflata, showed antimicrobial activity. Among them, licochalcone A and C had potent activity against some Gram-positive bacteria. These retrochalcones inhibited oxygen consumption in susceptible bacterial cells. The oxidation of NADH in bacterial membrane preparations was also inhibited by them. NADH-cytochrome c reductase was inhibited by licochalcones, while cytochrome c oxidase was not. NADH-CoQ reductase and NADH-FMN oxidoreductase were not inhibited. The site of respiratory inhibition of licochalcones was thought to be between CoQ and cytochrome c in the bacterial respiratory electron transport chain.

Formation of a cycloinulo-oligosaccharide from inulin by an extracellular enzyme of Bacillus circulans OKUMZ 31B

A strain of Bacillus circulans OKUMZ 31B, isolated from soil, has been shown to produce an extracellular enzyme that converts inulin into cycloinulo-oligosaccharides. The main product was identified as cycloinulo-hexaose. The enzyme is arbitrarily designated as cycloinulo-oligosaccharide fructanotransferase.

Protection of mitochondrial functions against oxidative stresses by isoflavans from Glycyrrhiza glabra

Isoflavan derivatives, glabridin (1), hispaglabridin A (2), hispaglabridin B (3), 4′‐O‐methylglabridin (4) and 3′‐hydroxy‐4′‐O‐methylglabridin (5), isolated from Glycyrrhiza glabra, were investigated for their ability to protect liver mitochondria against oxidative stresses.

Two prenylated retrochalcones from Glycyrrhiza inflata

Two new chalcones, licochalcones C and D, were isolated from the root of Glycyrrhiza inflata (Leguminosae) together with three known chalcones echinatin, licochalcones A and B. Their structures were elucidated as 4,4′-dihydroxy-2-methoxy-3-prenylchalcone and 2-methoxy-3′-prenyl-3,4,4′-trihydroxychalcone, respectively, on a spectroscopic basis. All chalcones obtained from this plant are retrochalcones and lack an oxygen-functionality at the 2′-position. The biogenesis of retrochalcones is briefly discussed in relation to the chemotaxonomy of the genus Glycyrrhiza.

Application of Saponins in Foods and Cosmetics: Saponins of Mohave Yucca and Sapindus Mukurossi

Saponins are known as natural surfactants. In addition to this physical property, saponins exhibit a variety of biological activities, and have been investigated toward the development of new natural medicines and to prove the efficacy of traditional herbal medicines. As to the application of saponins to foods and cosmetics, it is indispensable that sufficient amounts of plant resouces are available, and that the content of saponins must be high. Furthermore, a plant must have a long history of human use as foodstuffs or ingredients of cosmetics, and their safety should be officially guaranteed.

Isolation and Synthesis of Two New 3-Arylcoumarin Derivatives from the Root of Glycyrrhiza Glabra (Licorice), and Structure Revision of an Antioxidant Isoflavonoid Glabrene

Abstract Two new 3-arylcoumarin derivatives were isolated from the root of Glycyrrhiza glabra (licorice; Fabaceae), and their structures were elucidated as 2′,4′-dihydroxy-[6″,6″-dimethylpyrano(2″,3″:7,8)]-3-arylcoumarin and [6′,6″-dimethylpyrano(2″,3″:7,8)]-2′-hydroxy-4′-methoxy-3-arylcoumarin on the basis of spectroscopic evidence. Chemical syntheses of these two pyrano-3-arylcoumarins are described. Two other known isoflavonoids glabrene and glabrone were also obtained, and the structure of the former is revised based on 13C-NMR analysis and NOE experiments.

Application of Saponin-Containing Plants in Foods and Cosmetics

Saponins are a class of natural products which are structurally constructed of aglycone (tri‐ terpene or steroid) and sugars (hexose and/or uronic acid). The name ‘saponin’ comes from soap as its containing plants agitated in water form soapy lather. Saponins are widely dis‐ tributed in many plants and are relatively widespread in our foodstuffs and herbal prepara‐ tions. Saponins traditionally used as a natural detergent. In addition to this physical property, plant-derived triterpenoid and steroidal saponins have historically received a number of industrial and commercial applications ranging from their use as sources of raw materials for the production of steroid hormones in the pharmaceutical industry, to their use as food additives and as ingredients in photographic emulsions, fire extinguishers and other industrial applications which take advantage of their generally non-ionic surfactant proper‐ ties [1-3]. They also exhibit a variety of biological activities, and have been investigated to‐ ward the development of new natural medicines and prove the efficacy of traditional herbal medicines [4]. Other interesting biological applications for various specific saponins include their uses as anti-inflammatory [5], hypocholesterolemic [6] and immune-stimulating [7] whose properties are widely recognized and commercially utilized.

Antitumor-Promoting Activities of Dihydroflavonols from Kohki Tea, the Leaves of Engelhardtia chrysolepis

The leaves of Engelhardtia chrysolepis Hance (kohki in Japanese) have been used as a folk medicine and health-giving tea in the southern region of China. In the course of studies on foods and food ingredients for health supplements, the extracts and dihydroflavonoids of kohki tea were found to show several activities such as antioxidation and suppression of active oxygen and lipid peroxidation, as well as antiallergy-, antiinflammation-, and antitumor-promoting actions, which relate to the prevention of cancer and other diseases. The antitumor-promoting actions of principles and extracts of kohki tea were substantiated by two-stage carcinogenesis induced in experimental models. The topical application of a main constituent, astilbin, and its aglycone, (+)-taxifolin, inhibited 7,12-dimethylbenz[a] anthracene (DMBA)/12–0-tetradecanoyl-phorbol-13-acetate (TPA)-induced mouse skin tumors. Further, in 4-nitroquinoline-N-oxide (4NQO)/glycerol-induced mouse pulmonary carcinogenesis and DMBA/ultraviolet irradiation-induced mouse skin carcinogenesis, the oral administration of kohki tea extracts, astilbin, and (+)-taxifolin were effective in preventing tumor formation.