Tetsuya Suzuki

Gastrointestinal absorption and metabolism of capsaicin and dihydrocapsaicin in rats

Gastrointestinal absorption of capsaicin and dihydrocapsaicin was studied in rats in vivo and in situ. Rapid absorption of capsaicin or dihydrocapsaicin from stomach and small intestine occurred in vivo. About 85% of the dose was absorbed in the gastrointestinal tract within 3 hr. In situ, within 60 min after the administration of capsaicin and dihydrocapsaicin into stomach, jejunum, and ileum, about 50, 80, and 70% of the respective dose had disappeared from the lumen. When 2,4-dinitrophenol or NaCN was added, no significant reduction in uptake of [3H]dihydrocapsaicin was observed in the jejunum. These results suggested that capsaicin and its analogs were absorbed by a nonactive process in jejunum. [3H]Dihydrocapsaicin was mainly absorbed via the portal system but not a mesenteric lymphangial one. The radioactivity in the portal blood was composed of 85% of [3H]dihydrocapsaicin and 15% of its metabolite (8-methyl nonanoic acid) bound to the albumin fraction. Dihydrocapsaicin-hydrolyzing enzyme activity was found in jejunal tissue. These results suggest that capsaicin and its analogs partly received a first-pass effect, i.e., metabolism of a compound following first absorption in the gastrointestinal tract. It is concluded that capsaicin and its analogs are readily transported to the portal vein through the gastrointestinal tract by a nonactive process and partly metabolized during absorption.

Effects of glucose and its oligomers on the stability of freeze-dried liposomes.

The effects of glucose and its oligomers (maltodextrins) on the stability of sonicated liposomes during freeze-drying were studied by monitoring the retention of the fluorescent dye, Calcein, entrapped in the liposomal inner aqueous phase and by the use of differential scanning calorimetry (DSC). Glucose showed weak cryoprotective effects on dioleoylphosphatidylcholine (DOPC) or egg yolk phosphatidylcholine (eggPC) liposomes, while it had a relatively high cryoprotective effect on dipalmitoylphosphatidylcholine (DPPC) liposomes. Maltose and maltotriose showed high cryoprotective effects on eggPC liposomes, while other maltodextrin, longer oligomers, showed low cryoprotective effects. No saccharide was effective to protect DOPC liposomes. The fluidity and/or packing of lipid membranes had considerable influences on the stability of liposomes during the lyophilization. Maltodextrins showed relatively high cryoprotective effects on DPPC liposomes at low saccharide/lipid molar ratios, although the cryoprotective effects decreased with the increase in the molar ratios. Size measurements suggested that glucose and maltose completely prevented the aggregation and/or fusion of liposomes during lyophilization, and that other maltodextrins induced them due to their weak hydrophobic properties.

Identification of vasopressor phospholipid in crude soybean lecithin

The vasopressor phospholipid in crude soybean lecithin was isolated by column chromatography on Sephadex LH-20. It represented 0.1% of crude soybean lecithin. The isolated phospholipid was identified to be lysophosphatidic acid by gas chromatography-mass spectrometry analysis of TMS-deacylated product and acetolysis product. Nuclear magnetic resonance analysis favored the 1-monoacyl isomer over the 2-isomer. By enzymic determination with L-3-glycerophosphate dehydrogenase, the isolated phospholipid was identified as 1-monoacyl-L-3-glycerophosphate. Gas chromatographic examination revealed that it was composed of a large percentage of unsaturated fatty acids, especially linoleic acid. The activity of isolated lysophosphatidic acid was slightly less than that of synthetic 1-linoleoyl-L-3-glycerophosphate.

Simultaneous microdetermination of capsaicin and its four analogues by using high-performance liquid chromatography and gas chromatography—mass spectrometry

An improved method is described for the simultaneous determination of capsaicin and its analogues at levels from nanograms to micrograms using high-performance liquid chromatography (HPLC) and gas chromatography--mass spectrometry. This method consists of two steps: firstly, purification and determination of total capsaicinoid by HPLC, and secondly, the simultaneous determination of capsaicin and its analogues by mass chromatography (MC) or mass fragmentography (MF). Crude extracts of capsaicinoid were purified with a Zorbax SIL column. Total capsaicinoid was detected at 235 nm and measured automatically by a microcomputer. It was collected, evaporated, trimethylsilylated and subjected to MC or MF. After monitoring the molecular ions of trimethylsilyl derivatives of capsaicinoid and the internal standard, the absolute contents of each analogue were determined by computer. By using this method, capsaicin and all of its analogues can be determined simultaneously at levels from micrograms to nanograms without any interferences from other components.

Quantitative microanalysis of capsaicin, dihydrocapsaicin and nordihydrocapsaicin using mass fragmentography

A mass fragmentographic method for the quantitative microanalysis of capsaicin, dihydrocapsaicin and nordihydrocapsaicin in the fruits of Capsicum annuum has been developed. The molecular ions at m/e 377, 379 and 365 in the mass spectra were used for monitoring the trimethylsilyl derivatives of capsaicin, dihydrocapsaicin and nordihydrocapsaicin, respectively. The ratios of the height of each molecular ion to that of an internal standard (cholestane) were linear over the range 5-60 ng. The purification of individual capsaicinoids by high-performance liquid, thin-layer and gas-liquid chromatography is also described.

Determination of molecular species of ovolecithin using gas chromatography-mass spectrometry

An analysis of monoacetyldiglyceride was performed by gas chromatographymass spectrometry for the purpose of determining the molecular species of ovolecithin. Separation of monoacetyldiglycerides was made according to the degree of unsaturation and to the sum of the carbon numbers of fatty acyl residues. Fragments of monoacetyldiglyceride were analyzed and interpreted in relation to the molecular structure in a similar manner to that of triglyceride.

Deamination and γ-addition reactions of vinylglycine by L-methionine γ-lyase

Nobuyoshi Esaki, Tetsuya SUZUKI*, Hidehiko TANAKA +, Kenji SODA* and Robert R. RANDO** Laboratory of Microbial Biochemistry, Institute for Chemical Research, Kyoto University, Uji, Kyoto-Fu 611, *Research Institute for Food Science, Kyoto University, Ufi, Kyoto-Fu 611, +Laboratory of Biochemistry, Kyoto College of Pharmacy, Kyoto 607, Japan and **Department of Pharmacology, Harvard Medical School, Boston, MA 02115, USA

Examination of acetolysis products of phosphatidylcholine by gas chromatography-mass spectrometry

A comparison of monoacetyldiglycerides obtained from authentic phosphatidylcholines by acetolysis with those obtained by phospholipase C-acetylation was made to examine the intermolecular acyl migration, the intramolecular acyl migration between C-1 and C-2, and the formation of 1,3-isomer in the acetolysis reaction. Egg yolk phosphatidylcholine also was used. It was revealed that in acetolysis, the intermolecular acyl migration and selective degradation of polyunsaturated fatty acids did not take place at all. The intramolecular acyl migration, including the formation of 1,3-isomer, occurred to a small extent. Appreciable difference was not found in comparison of molecular species compositions of monoacetyldiglycerides derived by both methods from egg yolk phosphatidylcholine, except small differences found in the contents of two kinds of molecular species.

Deuterium isotope effects on the formation of mercapturic acids from lindane in rats

Abstract Metabolism experiments with rats showed that significant isotope effects ( k H k D = 2.4 to 3.5 ) were associated with the in vivo formation of dichloro and trichlorophenylmercapturic acids from a 1:1 mixture of normal and hexadeuterated lindane. This is evidence that rate-determining dehydrogenation and dehydrochlorination, both of which proceed with significant isotope effects, are essential in the pathway of dichloro- and trichlorophenylmercapturic acid formation from lindane. No significant primary isotope effects were associated ( k H k D = 1.31 ± 0.17 ) with the formation of monochlorophenylmercapturic acid. This suggests that the 1,2-dechlorination to tetrachlorocyclohexene followed by glutathione conjugation is the probable pathway that produces this metabolite from lindane.

Isolation and characterization of 6-hydroxymethylpterin as the Crithidia growth-promoting factor from spinach chloroplasts☆

2-Amino-4-hydroxypteridine compounds were isolated as the Crithidia factor from spinach chloroplasts by DEAE-Sephadex A-50, DEAE-cellulose, Sephadex G-25, and thin-layer chromatography. One of the compounds was characterized as 6-hydroxymethylpterin by gas-liquid chromatography-mass spectrometry and by comparison with authentic specimen.