Hideaki Ohta

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.

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%.

Thin-layer and high-performance liquid chromatographic analyses of limonoids and limonoid glucosides in Citrus seeds

Abstract A routine method for the analysis of limonoids and limonoid glucosides in citrus seeds, which utilizes thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC), is described. Seed meals were washed with n-hexane to remove oily materials, after which limonoids and limonoid glucosides were extracted with acetone and then methanol. The methanol extract contains the remainder of the limonoid aglycones and all limonoid glucosides. After the methanol was evaporated off, the residue was extracted with methylene chloride-water (1:1). The limonoids of both the acetone and methylene chloride fractions were separated and quantified by HPLC. The total limonoid glucoside content of the water fraction was determined by silica gel TLC. Each of the limonoid glucosides was then eluted from the reversed-phase HPLC column by a linear gradient system starting at 15% acetonitrile in 3 mM phosphoric acid and ending with 26% acetonitrile after 35 min, and quantitated by spectrophotometric detection at 210 nm. The limonoid aglycones and limonoid glucosides in two kinds of citrus seeds, Shiikuwasha (Citrus depressa) and Iyo (Citrus iyo), were determined. The content of limonoid glucosides in Shiikuwasha was found to be approximately two-fold higher than that of Iyo.

Limonoids in seeds of Citrus hanaju

The amounts of limonoids and their glucoside derivatives present in seeds of Citrus hanaju hort. ex. Shirai were determined. The seeds contained deacetylnomilin, limonin, nomilin and obacunone in order of decreasing concentration. They also contained the 17-β-d-glucopyranosides of deacetylnomilin, deacetylnomilinic acid, obacunone, ichangin, isolimonic acid, nomilinic acid and nomilin. Although C. hanaju has been classified in the group of cultivars related to C. ichangensis, the seeds did not possess ichangensin or its glucoside derivative, which are unique to C. ichangensis and its hybrids.

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.

Putrescine accumulation in banana fruit with ripening during storage.

Abstract Considerable accumulation of the free polyamine, putrescine (Put), was found in both pulp and peel tissue of unchilled and rewarmed bananas (Musa AAA group) during normal fruit ripening with climacteric ethylene production, while free Put remained at the original level in continuously chilled fruit. The bound Put content in both tissues of the unchilled and rewarmed fruits increased ca 3–10 fold. No competitive relationship was observed between Put and ethylene production in the banana fruit.

A Simple Determination of Thiamine in Rice (Oryza Sativa L) by High-Performance Liquid Chromatography with Post-Column Derivatization

Abstract We report a rapid high-performance liquid chromatographic method for the determination of thiamine in rice with fluorimetric post-column derivatization. The analysis system consisted of a combination of both thiamine extraction with a mixture of 0.1 M hydrochloric acid-40% methanol (0.1 M HCI-40% MeOH) solution from rice flour, and chromatographic separation and determination. To extract thiamine, the rice flour was refluxed for 30 min at 60 °C with 0.1 M HCl-40% HCI. The separation systems constituted of a Sorbax TMS column, column oven (55°C), elution system containing a mixture of 0.01 M sodium dihydrogen phosphate and 0.5 M sodium perchlorate solution, a mixing coil for chemical reaction and a spectrofluorimetric detector. The thiamine derivative compound was detected at 375 nm for excitation and 435 nm for emission. The recovery of thiamine was 94 -101%. The contents of thiamine in rice of six cultivars produced in Japan were determined by the above-mentioned HPLC method and AOAC method. The...

Putrescine accumulation in wounded green banana fruit

The concentrations of putrescine (Put) and ethylene, and the effects of biosynthesis inhibitors on the production of polyamines and ethylene were examined in wounded pulp tissue of green banana fruit. The Put concentration in the sliced banana fruit, and the arginine decarboxylase (ADC, EC 4.1.1.19) activity increased with the increase of ethylene evolution. Difluoromethylarginine (DFMA) suppressed Put accumulation by 72% while difluoromethylornithine (DFMO) had no effect on the Put content. Methylglyoxal bis(guanylhydrazone) (MGBG) decreased ethylene production and suppressed Put accumulation. Aminooxyacetic acid (AOA) and norbornadiene (NBD) also depressed Put accumulation. These findings suggest that ethylene produced in the wounded pulp tissue affects the induction of ADC and the accumulation of Put.

Homologs of the aflatoxin biosynthetic gene ver-1 in strains of Aspergillus oryzae and related species☆

Abstract Partial nucleotide sequences of two ver-1 homologs in Aspergillus parasiticus SYS-4 were analyzed. One of the homologs appeared to have a termination codon at amino acid position 87 and seems to be a non-functional pseudogene. Comparison of the nucleotide sequence between the another ver-1 homolog of SYS-4 and ver-1 of A. parasiticus NRRL 5862 led to identification of a frameshift within an exon; thus a part of amino acid sequences for the ver-1 homolog of SYS-4 and ver-1 of NRRL 5862 seems to differ greatly. With the ver-1 region of SYS-4 as a probe, DNA homologous to ver-1 was detected in some strains of Aspergillus oryzae and Aspergillus sojae , which are non-aflatoxin-producers, in addition to strains of Aspergillus flavus and A. parasiticus .