No abstract

A substance that exhibited a tryptophan-like fluorescence peak at 354 nm on excitation at 295 nm at neutral pH was isolated from human urine. This compound was determined by visible-light absorption spectroscopy, fluorescence spectroscopy, 1H and 13C NMR spectroscopies, and FAB-MS to be 1-(1',2',3',4',5'-pentahydroxypentyl)-1,2,3,4-tetrahydro-2-carboli ne-3- carboxylic acid. This compound, named tetrahydropentoxyline, is a new type of hydrophilic tetrahydro-beta-carboline, and its elution position was between those of 4-pyridoxic acid and kynurenic acid on C18 reversed-phase HPLC. The amount of tetrahydropentoxyline excreted in the urine of normal subjects [n = 21; age, 45 (SD 20) years] was about 5.2 (SD 1.0) mg per day.

BackgroundPeroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that regulate lipid and glucose metabolism. PPARα is highly expressed in the liver and controls genes involved in lipid catabolism. We previously reported that synthetic sphingolipid analogs, part of which contains shorter-length fatty acid chains than natural sphingolipids, stimulated the transcriptional activities of PPARs. Sphingosine and dihydrosphingosine (DHS) are abundant sphingoid bases, and ceramide and dihydroceramide are major ceramide species in mammals. In contrast, phytosphingosine (PHS) and DHS are the main sphingoid bases in fungi. PHS and phytoceramide exist in particular tissues such as the epidermis in mammals, and involvement of ceramide species in PPARβ activation in cultured keratinocytes has been reported. The purpose of the present study is to investigate whether natural sphingolipids with C18 fatty acid and yeast-derived sphingoid bases activate PPARs as PPAR agonists.MethodLipids of brewer's yeast contain PHS- and DHS-based sphingolipids. To obtain the sphingoid bases, lipids were extracted from brewer's yeast and acid-hydrolyzed. The sphingoid base fraction was purified and quantified. To assess the effects of sphingolipids on PPAR activation, luciferase reporter assay was carried out. NIH/3T3 and human hepatoma (HepG2) cells were transfected with expression vectors for PPARs and retinoid × receptors, and PPAR responsive element reporter vector. When indicated, the PPAR/Gal4 chimera system was performed to enhance the credibility of experiments. Sphingolipids were added to the cells and the dual luciferase reporter assay was performed to determine the transcriptional activity of PPARs.ResultsWe observed that phytoceramide increased the transcriptional activities of PPARs significantly, whereas ceramide and dihydroceramide did not change PPAR activities. Phytoceramide also increased transactivation of PPAR/Gal4 chimera receptors. Yeast-derived sphingoid base fraction, which contained PHS and DHS, or authentic PHS or DHS increased PPAR-dependent transcription. Additionally, phytoceramide stimulated PPARα activity in HepG2 hepatocytes, suggesting that phytoceramide activates genes regulated by PPARα.ConclusionsPhytoceramide and yeast-derived sphingoid bases activate PPARs, whereas ceramide and dihydroceramide do not change the PPAR activity. The present findings suggest that phytoceramide acts as a PPAR ligand that would regulate PPAR-targeted genes.

. Can. J. Chem. 59,2677Chem. 59, (1981. Plant tissue cultures of Tripterygium wilfordii Hook F produced the cytotoxic diterpene triepoxides tripdiolide (1) and triptolide (2) in yields that were 16 and 3 times greater, respectively, than those observed in the plant itself. Other diterpenes, dehydroabietic acid (3) and 15-hydroxy-18-norabieta-3,8,11,13-tetraene-3-oic acid methyl ester (4) were also isolated. Co-occuring in these cultures were the cytotoxic quinone-methides, celastrol(5), compound 6, and compound 7. Other triterpenes produced were oleanolic acid (8) and polpunonic acid (9). p-Sitosterol(17) was also isolated. The proposed structure of 4 was confirmed by synthesis startingfrom compound 3. Cytotoxic data are reported, and a possible biosynthetic relationship among dehydroabietic acid, compound 4, and tripdiolide (1) is presented.

The antiallergic properties of hop water extract (HWE) were studied by evaluating histamine release from human basophilic KU812 cells induced by calcium ionophore A23187. HWE significantly inhibited histamine release, but boiling water extract and chloroform-methanol extract did not show any inhibitory effect on it. A 50% methanol-eluted fraction separated from HWE by XAD-4 column chromatography (MFH) had a strong inhibitory effect as compared with HWE. Quercetin glycosides and kaempherol glycosides were identified in MFH, of which quercetin glycosides contributed to the inhibition of histamine release. Most quercetin in HWE existed in glycoside form and its quercetin content, obtained by acid hydrolysis, was about 200 mug/g. HWE and MFH significantly inhibited protein kinase C, which plays a pivotal role in the degranulation of chemical mediators. These results indicate that HWE can inhibit type-I allergic reactions.