Yoichi Nogata

Flavonoid Composition of Fruit Tissues of Citrus Species

An HPLC analysis was performed on the concentrations of flavonoids in 42 species and cultivars of the Citrus genus and those of two Fortunella and one Poncirus species according to the classification system established by Tanaka. The composition of 8 flavanones and 9 flavone/ols for these species was determined in the albedo, flavedo, segment epidermis and juice vesicle tissues, and those in the fruit and peel tissues were calculated from the composition data of the tissues. A principal component analysis showed that such neohesperidosyl flavonoids as neoeriocitrin, naringin, neohesperidin, and rhoifolin had large factor loading values in the first principal component for each tissue. The flavonoid composition of citrus fruits was approximately the same within each section of Tanaka’s system, except for the species in the Aurantium section and those with a peculiar flavonoid composition such as Bergamot (C. bergamia), Marsh grapefruit (C. paradisi), Sour orange (C. aurantium), and Shunkokan (C. shunkokan). The Aurantium section included both naringin-rich and hesperidin-rich species.

Polygalacturonase in strawberry fruit.

Abstract A low level of exo- and endo-polygalacturonase has been found in strawberry fruit (Fragaria ananassa, Duch. cv. Toyonoka). The activity was shown t

High-performance liquid chromatographic determination of naturally occurring flavonoids in Citrus with a photodiode-array detector

Abstract High-performance liquid chromatography (HPLC) coupled with ultraviolet-visible spectrophotometry using a photodiode-array detector was used as a routine method for the simultaneous separation and determination of 25 naturally occurring Citrus flavonoids. The separation system consisted of a C18 reversed-phase column, a gradient system of 0.01 M phosphoric acid (A) and methanol (B), and a photodiode-array detector. Each of the 25 flavonoids was eluted from the column with a gradient system composed of three periods: (1) 0–55 min, 70-55% (v/v) A in B, (2) 55–95 min, 55-0% A in B, and (3) 95–100 min, isocratic, 100% B, and quantified by spectrophotometric detection at 285 nm. Identifications of specific flavonoids were made by comparing their retention times (tR) and UV spectra with those of standards. The relative standard deviations of tR, values were 0.029–0.321%. The recoveries of pure eriocitrin, naringin, hesperidin and tangeretin added to tissues prepared from Unshiu (Citrus unshiu Marc.) and Hirado-buntan (Citrus grandis Osbeck f. Hirado) and subsequent extraction were 97.47–103.13% from the mesocarp and 96.87–104.93% from the juice with standard deviations of 2.32–5.72% and 2.18–5.96%, respectively.

Directed deletions in the aflatoxin biosynthesis gene homolog cluster of Aspergillus oryzae.

To investigate the structure of the aflatoxin gene cluster in Aspergillus oryzae, 39 strains belonging to this species were examined for the existence of pksA, fas-1A, aflR and vbs, and the results compared with those for ver-1 obtained previously. These five genes are involved in aflatoxin biosynthesis in Aspergillus parasiticus. The strains examined were categorized into three groups; group 1, having the five homologs; 2, having ver-1 and vbs; and 3, having vbs homologs. Long-PCR analysis of the regions between the five homologs in A. oryzae IFO 4135, coupled with Southern-hybridization analysis, shows that those homologs are clustered with the same arrangement as in A. parasiticus. These results suggest that directed deletions of the cluster occur in A. oryzae strains. The possible breakpoints of the deletions in the strains of group 2 and 3 were estimated.

Angiotensin I converting enzyme inhibitory peptides produced by autolysis reactions from wheat bran.

The production of angiotensin I converting enzyme (ACE) inhibitory peptides by autolysis reactions from wheat milling byproducts was investigated. Milled whole grain, bran, shorts, and red dog acquired ACE inhibitory activity though water soaking treatment. Among the milled fractions, the preparation of shorts exhibited the strongest inhibitory activity (IC50 = 0.08 mg protein/mL) followed by that of bran, red dog, and whole grain in decreasing order. The production of ACE inhibitory peptides was almost completely inhibited by pepstatin A, indicating the contribution of aspartic proteases. The optimal pH for acquiring ACE inhibitory activity of the byproduct fraction (mixtures of bran and shorts) was 3.2. The level of inhibitory activity rose with increasing temperature up to 40 degrees C. The inhibitory activity reached a maximal level after a 12 h reaction time and maintained the same level up to 24 h at 40 degrees C, pH 3.2. From the hydrolysate of the byproduct fraction, six peptides were isolated by several steps of chromatography, and their amino acid sequences were Leu-Gln-Pro, Ile-Gln-Pro, Leu-Arg-Pro, Val-Tyr, Ile-Tyr, and Thr-Phe. Thus, wheat milling byproducts have the possibility to become an effective source for ACE inhibitory peptides.

High-performance liquid chromatographic determination of polyamines in selected vegetables with postcolumn fluorimetric derivatization

Abstract A rapid high-performance liquid chromatographic analysis for the simultaneous separation of five naturally occurring polyamines (agmantine, putrescine, cadaverine, spermidine and spermine) is described. Postcolumn derivatization with o-phthalaldehyde is used. The separation systems consisted of a strong cation-exchange column, an elution buffer consisting of 1 M sodium citrate (pH 5.4), a mixing coil for the chemical reaction and a spectrofluorimetric detector. The derivatized fluorescent compounds were detected at 340 nm (excitation) and 455 nm (emission). The recoveries of the polyamines were 94.5–107.0% with a standard deviation of 0.83–7.65%.

Aspergillus oryzae with and without a homolog of aflatoxin biosynthetic gene ver-1

Abstract Part of the nucleotide sequence of the ver-1 homolog in each of two strains of Aspergillus oryzae, Aspergillus sojae, and Aspergillus flavus were compared with two homologs in Aspergillus parasiticus. The homologs in A. oryzae and A. sojae (non-aflatoxin-producers) exhibited an extremely high degree (93.8–99.8% for A. oryzae, and 96.0–99.5% for A. sojae) of sequence identity with that of A. flavus and A. parasiticus. No two strains within the same species, except A. sojae, were identical. No sequence fingerprint was found to distinguish between A. oryzae and A. flavus, or between A. sojae and A. parasiticus. The predicted partial amino acid sequences (181 amino acids) of the ver-1 homologs had at most two amino acid changes relative to A. parasiticus SYS-4 ver-1. Transcripts of ver-1 homologs in the strains of A. oryzae and A. sojae examined were not detected by the polymerase chain reaction coupled with reverse transcription. By Southern analysis, a total of 46 strains of A. oryzae were examined for the presence of the ver-1 homolog. The homolog was detected in 38 strains, but not in 8 strains. Morphologically, strains with and without the ver-1 homolog were indistinguishable. Thus, A. oryzae contains strains with and without a homolog of the aflatoxin biosynthetic gene ver-1.

Inhibitors of platelet lipoxygenase from Ponkan fruit

An activity-guided separation for inhibitors of rat platelet 12-lipoxygenase led to the isolation of two compounds, 4-O-feruloyl-5-O-caffeoylquinic acid (IC50; 5.5 microM) and methyl 4-O-feruloyl-5-O-caffeoylquinate (IC50; 1.9 microM) from the peel of Ponkan fruit (Citrus reticulata). The complete structure of each phenolic ester was determined by NMR spectroscopy [1H and 13C NMR spectra, 1H-1H correlation spectroscopy (COSY), 1H-detected heteronuclear multiple quantum coherence (HMQC), and heteronuclear multiple bond connectivity (HMBC) spectroscopies] and other spectral methods.

Production of Free Amino Acids and γ-Aminobutyric Acid by Autolysis Reactions from Wheat Bran

To find added value for wheat-milling byproduct, an approach for producing free amino acids and gamma-aminobutyric acid (GABA) was examined. Milled whole grain, bran, shorts, red dog, and 60% extracted flour all released amino acids using a water-soaking treatment. Little difference was found in amino acid production yield from whole grain between the soft and hard wheat cultivars investigated. Among the milled fractions, shorts produced the largest amount of total amino acids followed by bran, red dog, and 60% extracted flour in decreasing order. From the byproduct fraction (mixture of bran and shorts), leucine (Leu), arginine (Arg), valine (Val), lysine (Lys), glutamine (Gln), phenylalanine (Phe), isoleucine (Ile), and GABA were produced at 486, 421, 316, 329, 321, 279, 227, and 118 mg/100 g, respectively, in 120 h at 40 degrees C. Optimal pH for the byproduct fraction was 3.5-5.0 for alpha-amino acids and 5.5 for GABA. The production levels rose with increasing temperature up to 40-50 degrees C for alpha-amino acids and up to 40 degrees C for GABA. The yield of all amino acids increased in the experimented period until 120 h except for aspartic acid (Asp) and asparagine (Asn). Thus, wheat-milling byproducts have the potential to become effective materials for developing foods enriched in branched-chain amino acids (BCAA), Arg, Lys, Gln, Phe, and GABA.

Changes in molecular weight and carbohydrate composition of cell wall polyuronide and hemicellulose during ripening in strawberry fruit

Abstract Polyuronides and hemicelluloses from the cell wall of developing strawberry fruit ( Fragaria ananasa , Duch. cv. Toyonoka) were examined for molecular weight distribution, and carbohydrate composition prior to and following gel filtration chromatography. In non-fractionated polyuronides, the galacturonic acid and arabinose concentrations decreased during development. The concentration of rhamnose markedly increased, whereas that of arabinose declined in low-molecular-weight polyuronides ( M r kDa ). A significant reduction of hemicelluloses was detected in the high-molecular-weight region ( M r >170 kDa ), whereas little change was observed in the sugar composition of these polymers. Polygalacturonase activity was consistently reduced during ripening.