Makio Shibano

Antioxidant constituents in the dayflower (Commelina communis L.) and their α-glucosidase-inhibitory activity

The dayflower, Commelina communis L., contains 1-deoxynojirimycin (DNJ) and (2R,3R,4R,5R)2,5-bis(hydroxymethyl)-3,4-dihydroxypyrrolidine (DMDP), potent α-glucosidase inhibitors. The extracts and powder of this herb are important food materials for prophylaxis against type 2 diabetes. Eleven flavonoid glycosides as antioxidants, isoquercitrin, isorhamnetin-3-O-rutinoside, isorhamnetin-3-O-β-d-glucoside, glucoluteolin, chrysoriol-7-O-β-d-glucoside, orientin, vitexin, isoorientin, isovitexin, swertisin, and flavocommelin, were identified from the aerial parts of C. communis. Their antioxidant activities were measured using in vitro assays employing the 1,1-diphenyl-2-picrylhydrazyl radical- and superoxide radical-scavenging assays. The results showed that glucoluteolin, orientin, isoorientin, and isoquercitrin are the predominant antioxidants in this herb. Moreover, isoquercitrin, isorhamnetine-3-O-rutinoside, vitexin, and swertisin inhibited the activity of α-glucosidase from rat intestine.

Piscidic acid and fukiic acid esters from Cimicifuga simplex

Abstract Investigation of the underground parts of Cimicifuga simplex afforded five new piscidic acid esters and two new fukiic acid esters: 2-caffeoyl piscidic acid, 2-feruloyl piscidic acid, 2-isoferuloyl piscidic acid, 2-feruloyl piscidic acid-1-methyl ester, 2-isoferuloyl piscidic acid-1-methyl ester, 2-feruloyl fukiic acid-1-methyl ester, and 2-isoferuloyl fukiic acid-1-methyl ester.

Avicularin, a plant flavonoid, suppresses lipid accumulation through repression of C/EBPα-activated GLUT4-mediated glucose uptake in 3T3-L1 cells.

Avicularin (quercetin-3-O-α-L-arabinofuranoside) is a plant flavonoid and a quercetin glycoside. In this study, we found that avicularin suppressed the accumulation of intracellular lipids through repression of glucose transporter 4 (GLUT4)-mediated glucose uptake in mouse adipocytic 3T3-L1 cells. Avicularin was highly purified (purity of more than at least 99%) from Taxillus kaempferi (DC.) Danser (Loranthaceae) by high-performance liquid chromatography, and its structure was determined by nuclear magnetic resonance and mass spectrometry. Avicularin decreased the intracellular triglyceride level along with a reduction in the expression of adipogenic genes such as peroxisome proliferator-activated receptor γ, CCAAT/enhancer-binding protein (C/EBP) α, and aP2 (fatty acid-binding protein 4). In contrast, avicularin did not affect the expression of lipogenic and lipolytic genes. Interestingly, the expression of the GLUT4 gene was significantly suppressed in an avicularin-concentration-dependent manner. Moreover, the binding of C/EBPα to the promoter region of the GLUT4 gene was repressed by adding avicularin to the medium in 3T3-L1 cells, as demonstrated by the results of a chromatin immunoprecipitation assay. These results indicate that avicularin inhibited the accumulation of the intracellular lipids by decreasing C/EBPα-activated GLUT4-mediated glucose uptake in adipocytes.

Furanocoumarin Derivatives in Kampo Extract Medicines Inhibit Cytochrome P450 3A4 and P-Glycoprotein

Furanocoumarins in grapefruit are known to show inhibitory effects against P-glycoprotein (P-gp) and CYP3A4 in intestinal epithelial cells; however, furanocoumarin derivatives are widely contained in the plants of Rutaceae and Umbelliferae families, which are used as components of Kampo extract medicines. In this study, we investigated the inhibitory effects of 12 furanocoumarins extracted from plants in the Umbelliferae family against P-gp and CYP3A4 activity. Furthermore, we studied their inhibitory effect on P-gp when furanocoumarins are used as Kampo extract medicine rather than as an isolated single compound. From screening of the CYP3A4 inhibitory effect, notopterol and rivulobirin A, the only dimer types of furanocoumarin, were found to be potent inhibitors of CYP3A4. On the other hand, byakangelicol and rivulobirin A showed strong P-gp inhibition from the screening of P-gp inhibitor evaluated by quinidine permeation through the Caco-2 monolayer; however, the chemical structural relationship of furanocoumarins between P-gp and CYP3A4 inhibitory effects could not be obtained. We also investigated the effect of these furanocoumarins on the transport of digoxin through the Caco-2 monolayer. The inhibitory effect of rivulobirin A was more potent than that of byakangelicol. Application of either Senkyu-cha-cho-san or Sokei-kakketsu-to, which are composed of herbal remedies in the Umbelliferae group, significantly decreased the efflux ratio of digoxin. In conclusion, it was found that some furanocoumarins extracted from the plants in the Umbelliferae family strongly inhibited P-gp and CYP3A4. Kampo extract medicines containing herbal remedies belonging to the Umbelliferae family may cause a drug-drug interaction with P-gp or a CYP3A4 substrate drug.

Chemical studies on the root of Heracleum candicans WALL.

Two new alkyl coumarins, isophellodenol C (1) and candinol A (2); four new spirobifuranocoumarins, candibirins B–E (3-6); and two trifuranocoumarins, canditririns A and B (7 and 8), were isolated from the roots of Heracleum candicans WALL. Their structures were established using chemical and spectral means.

Synergistic antitumor effect of a combination of paclitaxel and carboplatin with nobiletin from Citrus depressa on non-small-cell lung cancer cell lines.

Non-small-cell lung carcinomas do not sufficiently respond to cancer chemotherapeutic drugs. Combination effects of cancer chemotherapy drugs (paclitaxel and carboplatin) with nobiletin or powdered Shiikuwasha extract from Citrus depressa were examined by isobologram and combination index analyses. It was demonstrated that the combination generated a synergistic inhibitory effect against the proliferation of the human non-small-cell lung carcinoma cell lines A549 and H460 and that of the two chemotherapy drugs, paclitaxel was responsible for this synergistic effect. Furthermore, the percentage of apoptotic cells was decreased with increasing rates of nobiletin to paclitaxel and carboplatin. These findings were considered to be attributed to the ability of nobiletin to regulate cells in the G1 phase, which escaped cell death initiated by paclitaxel and carboplatin. An antitumor activity assay showed that this combination significantly suppressed the growth of subcutaneous A549 tumor xenografts in nude mice.

Determination of Flavonoids in Licorice Using Acid Hydrolysis and Reversed-Phase HPLC and Evaluation of the Chemical Quality of Cultivated Licorice

Licorice contains flavonoids and triterpenoids as the major bioactive components. Most of the flavonoids are the glycosidic form of liquiritigenin (LIQ), isoliquiritigenin (ISO) and formononetin (FOR). A reversed-phase HPLC method for the quantification of LIQ, ISO and FOR in licorice was developed. This method does not measure each glycoside but measures the aglycones using acid hydrolysis. All calibration curves showed good linear regression (r > 0.9998). The method showed good precision for intraday (RSD < 2.14 %) and interday (RSD < 0.51 %) assays. The limit of detection was 0.031 microg for LIQ, 0.011 microg for ISO and 0.006 microg for FOR. The limit of quantification was 0.31 microg for LIQ, 0.11 microg for ISO and 0.06 microg for FOR. The flavonoid contents along with the glycyrrhizin content of cultivated licorice from seedling plants in Japan and commercial wild licorice were investigated. This new method could be extremely useful for evaluating the quality of licorice.

Anti-tumor activity of new orally bioavailable 2-amino-5-(thiophen-2-yl)benzamide-series histone deacetylase inhibitors, possessing an aqueous soluble functional group as a surface recognition domain

New orally bioavailable 5-(thiophen-2-yl)-substituted 2-aminobenzamide-series histone deacetylase inhibitors were synthesized. These compounds possess a morpholine or piperadine-derived moiety as an aqueous soluble functional group. Among them, 8b, having a 4-ethyl-2,3-dioxopiperazine-1-carboxamide group as a surface recognition domain, showed promising inhibitory activities against HCT116 cell growth and HDAC1/2. Notably, unlike MS-275, this compound did not induce apoptosis in the cell cycle tests. We therefore conducted antitumor tests of 8b and MS-275 against HCT116 cell xenografts in nude mice. Compound 8b reduced the volume of tumor mass to T/C: 60% and 47% at 45 and 80mg/kg over 16days, respectively. These values were comparable to the rate (T/C: 51% at 45mg/kg) for MS-275. Furthermore, 8b, at neither 45 nor 80mg/kg, induced the weight loss which was observed in the mice given MS-275 at 45mg/kg.

Chemical studies on the root of Heracleum candicans Wall. (Part 3)

Two new ester coumarins, candinols B and C (1 and 2), and three new coumarin dimers, candibirins F–H (3–5), were isolated from the roots of Heracleum candicans Wall. Their structures were established by using chemical and spectral means.

New orally bioavailable 2-aminobenzamide-type histone deacetylase inhibitor possessing a (2-hydroxyethyl)(4-(thiophen-2-yl)benzyl)amino group

New 2-aminobenzamide-type histone deacetylase (HDAC) inhibitors were synthesized. They feature a sulfur-containing bicyclic arylmethyl moiety-a surface recognition domain introduced to increase in cellular uptake-and a substituted tert-amino group which affects physicochemical properties such as aqueous solubility. Compound 22 with a (2-hydroxyethyl)(4-(thiophen-2-yl)benzyl)amino group reduced the volume of human colon cancer HCT116 xenografts in nude mice to T/C 67% by oral administration at 45mg/kg, which was comparable to the rate (T/C 62%) for a positive control, MS-275. Western blot analyses as well as cell cycle and TUNEL assays by flow cytometry suggested that the two compounds inhibited the growth of cancer cells via similar mechanisms.