Isolation and characterization of a low molecular weight peptide contained in sourdough

To investigate a sourdough-specific peptide, low molecular weight peptides were extracted from sourdough. The peptide fraction was subjected to two kinds of chromatography to separate the peptides. Reverse-phase chromatography of the peptide fraction in the sourdough showed certain specific peptides. The specific peptide fraction was further separated by gel filtration chromatography. Liquid chromatography tandem mass spectrometry analysis identified one of the peptides as VPFGVG (six-mer). This sequence was estimated to occur at the 287-292 position of a low molecular weight glutenin subunit. The peptide (designed as SDP1) was produced by proteases derived from wheat flour. SDP1 showed angiotensin-converting enzyme (ACE) inhibitory activity, and the 50% inhibitory peptide concentration (IC50) was 336 microM. It is possible that the SDP1 peptide partially confers ACE inhibitory activity in sourdough.     

An effective and practical method of net settings in rearing tank to suppress hypermelanosis in Japanese flounder

In Japanese flounder aquaculture, hypermelanosis occurs widely on the blind side. Rearing flounders in a net-lined tank was recently reported to prevent hypermelanosis. To effectively apply this method to larger tanks for aquaculture farming, the net setting method was examined. Juvenile flounders without darkened areas on the blind side [total length (TL) 13 cm] were selected, and reared for 6 months (TL 32 cm). In the control tank without a net, the median value of darkened area ratio (darkened area to blind side area) was 46%. By only covering the tank bottom with slack net, the darkened area ratio was suppressed to 8%, less than 1/5 of that in the control tank. At the end of experiment, bottom coverage ratios of 0%, 10%, 30%, 50%, and 100% revealed a negative correlation between bottom net coverage and darkened area ratio. In this experiment, the darkening area in the tank with 50% bottom net coverage decreased to 1/3 of the control. Although the occurrence of hypermelanosis differs depending on the production lot, these results are expected to serve as a reference for selecting the suitable net size to meet the level of clearness of the blind side.

     

Tomato metabolism and porphyrin-catalyzed oxidation of pyriproxyfen

Investigation of the metabolism of [(14)C]pyriproxyfen [4-phenoxyphenyl (R,S)-2-(2-pyridyloxy)propyl ether] in tomato fruits (Lycopersicon esculentum Mill. cv. Ponterosa) was conducted by topical application of acetonitrile solution or emulsifiable concentration formulation three times at 35, 21, and 7 days before harvest. Most of the radioactivity remained on the fruit surface or in the plant tissues as intact pyriproxyfen with minor metabolites formed via hydroxylation at the 4'-position of the phenoxy ring or cleavage of ether linkages. The biomimic chemical oxidation model using iron porphyrin as a catalyst and hydrogen peroxide was found to well reproduce the primary metabolites detected in the metabolism study. The electrophilic reaction indices obtained by AM1 molecular orbital calculations supposing involvement of cytochrome P-450 were successfully applied to evaluate the potentially higher reactive sites in pyriproxyfen.     

Metabolism of fungicide diethofencarb in grape (Vitis vinifera L.): definitive identification of thiolactic acid conjugated metabolites

The metabolic fate of diethofencarb (isopropyl 3,4-diethoxycarbanilate) separately labeled with (14)C at the phenyl ring and 2-position of the isopropyl moiety was studied in grape (Vitis vinifera L.). The acetonitrile solution of (14)C-diethofencarb at a rate of 500 g a.i. ha(-)(1) was once applied topically to fruits or leaves at the maturity stage of fruits (PHI 35 days), and the plants were grown in the greenhouse until harvest. In the grape plants, diethofencarb was scarcely translocated to the untreated portion and was degraded more in the fruit as compared to the leaf. For the fruit, diethofencarb primary underwent O-deethylation at the 4-position of the phenyl ring to form the phenolic derivative, isopropyl 3-ethoxy-4-hydroxycarbanilate (0.9% of the total radioactive residue, TRR). This metabolite was successively transformed via conjugation with glucose at the phenolic hydroxy group (8.1-18.1% TRR) or with thiolactic acid at the 5-position of the phenyl ring (1.5-1.7% TRR). The thiolactic acid conjugate was further metabolized mainly to two different types of glucose conjugates at the 4-position of the phenyl ring (8.7-13.5% TRR) and the hydroxy group in the thiolactic acid moiety (6.4-7.3% TRR), as evidenced by (1)H NMR and atmospheric pressure chemical ionization-liquid chromatography-mass spectrometry together with cochromatographies with synthetic standards.