Emiko Kinoshita

Antihypertensive Effect of Peptide-Enriched Soy Sauce-Like Seasoning and Identification of Its Angiotensin I-Converting Enzyme Inhibitory Substances

We have developed a peptide-enriched soy sauce-like seasoning termed Fermented Soybean Seasoning (FSS), by modifying the process of soy sauce brewing. The FSS has a 2.7-fold higher concentration of total peptides than regular soy sauce. The angiotensin I-converting enzyme (ACE) inhibitory activity of FSS (IC(50) = 454 microg/mL) was greater than that of regular soy sauce (IC(50) = 1620 microg/mL). The FSS demonstrated antihypertensive effects both in spontaneously hypertensive rats and in Dahl salt-sensitive rats during continuous feeding. The ACE inhibitory substances were purified from FSS by reversed-phase chromatography. Ala-Trp IC(50) = 10 microM; Gly-Trp IC(50) = 30 microM; Ala-Tyr IC(50) = 48 microM; Ser-Tyr, IC(50) = (67 microM; Gly-Tyr, IC(50) = 97 microM; Ala-Phe, IC(50) = 190 microM; Val-Pro, IC(50) = (480 microM; Ala-Ile, IC(50) = 690 microM; Val-Gly, IC(50) = 1100 microM; and a nicotianamine, IC(50) = 0.26 microM. [corrected] The concentrations of these substances in the FSS were revealed to be higher than that of regular soy sauce through quantitative LC-MS/MS analysis.

Anti-influenza virus effects of elderberry juice and its fractions.

Elderberry (Sambucus nigra L.) has traditionally been used for treating influenza and colds. We evaluated the antiviral effect of concentrated juice of elderberry (CJ-E) on the human influenza A virus (IFV). CJ-E had a relatively strong effect on IFV-infected mice, although its anti-IFV activity was weak in a cell culture system. The in vivo anti-IFV activities of the fractions were determined after separating CJ-E by ultrafiltration and anion-exchange chromatography. Oral administration of the high-molecular-weight fractions of CJ-E to IFV-infected mice suppressed viral replication in the bronchoalveolar lavage fluids (BALFs), and increased the level of the IFV-specific neutralizing antibody in the serum, as well as the level of secretory IgA in BALFs and feces. Fr. II from high-molecular-weight fraction HM, which contained acidic polysaccharides, showed relatively strong defense against IFV infection. We conclude that CJ-E had a beneficial effect by the stimulating immune response and preventing viral infection.

Differentiation of Soy Sauce Types by HPLC Profile Pattern Recognition

Nonvolatile minor components in various brands of Japanese fermented soy sauce were analyzed by gradient RP-HPLC and monitored at 280 nm. Chemometric pattern recognition techniques, such as cluster analysis, linear discriminant analysis (LDA), LDA using genetic algorithm (GA-LDA) and soft independent modelling of class analogy (SIMCA), succeeded in differentiating the resulting HPLC profiles according to soy sauce brands. Three components playing key roles in the differentiation were isolated by preparative HPLC and purified by gel-filtration chromatography, or simply repeated preparative HPLC. FAB-MS, 1H-, 13C-NMR and IR spectra suggested that these three components having molecular weights of 386, 402 and 418 were isoflavone derivatives. By applying HMBC spectral analysis, these isoflavones were identified as conjugated ethers of tartaric acid with daidzein, genistein and 8-hydroxygenistein. These new isoflavone derivatives are produced by some strains of Aspergillus fungi.

Inhibition of Glucose Transport by Tomatoside A, a Tomato Seed Steroidal Saponin, through the Suppression of GLUT2 Expression in Caco-2 Cells

We investigated whether tomatoside A (5α-furostane-3β,22,26-triol-3-[O-β-d-glucopyranosyl (1→2)-β-d-glucopyranosyl (1→4)-β-d-galactopyranoside] 26-O-β-d-glucopyranoside), a tomato seed saponin, may play a role in the regulation of intestinal glucose transport in human intestinal Caco-2 cells. Tomatoside A could not penetrate through Caco-2 cell monolayers, as observed in the transport experiments using liquid chromatography-mass spectrometry. The treatment of cells with 10 μM tomatoside A for 3 h resulted in a 46.0% reduction in glucose transport as compared to untreated cells. Western blotting analyses revealed that tomatoside A significantly (p < 0.05) suppressed the expression of glucose transporter 2 (GLUT2) in Caco-2 cells, while no change in the expression of sodium-dependent glucose transporter 1 was observed. In glucose transport experiments, the reduced glucose transport by tomatoside A was ameliorated by a protein kinase C (PKC) inhibitor and a multidrug resistance-associated protein 2 (MRP2) inhibitor. The tomatoside A-induced reduction in glucose transport was restored in cells treated with apical sodium-dependent bile acid transporter (ASBT) siRNA or an ASBT antagonist. These findings demonstrated for the first time that the nontransportable tomato seed steroidal saponin, tomatoside A, suppressed GLUT2 expression via PKC signaling pathway during the ASBT-influx/MRP2-efflux process in Caco-2 cells.