Gerhard Erben

Characterization and quantitation of polyphenolic compounds in bark, kernel, leaves, and peel of mango (Mangifera indica L.).

The contents of secondary plant substances in solvent extracts of various byproducts (barks, kernels, peels, and old and young leaves) in a range of Brazilian mango cultivars were identified and quantitated. The results show that the profiles of secondary plant substances such as xanthone C-glycosides, gallotannins, and benzophenones in different byproducts vary greatly but are fairly consistent across cultivars. The free radical scavenging activity of the solvent extracts was evaluated using a high-performance liquid chromatography-based hypoxanthine/xanthine oxidase assay and revealed dose-dependent antioxidant capacity in all extracts. Four (mangiferin, penta- O-galloyl-glucoside gallic acid, and methyl gallate) of the major phenolic compounds detected were also evaluated in additional in vitro bioassay systems such as oxygen radical absorbance capacity, 2,2-diphenyl-1-picrylhydrazyl, and ferric reducing ability of plasma. Mangiferin in particular, detected at high concentrations in young leaves (Coite = 172 g/kg), in bark (Momika = 107 g/kg), and in old leaves (Itamaraka = 94 g/kg), shows an exceptionally strong antioxidant capacity.

Isolation and structure elucidation of the major individual polyphenols in carob fibre.

Although it is already known that carob fibre contains several classes of polyphenolic substances, a comprehensive analysis of these has not been conducted to date. Therefore, the major polyphenolic compounds were extracted with organic solvents, and, following fractionation by normal-phase column chromatography on silicic acid, their structures were elucidated by liquid-chromatography electrospray-ionisation mass spectrometry (LC-ESI), nano-electrospray-ionisation mass spectrometry (ESI-MS), and gas-chromatography mass spectrometry (GC-MS). In addition, complete 1H and 13C NMR assignments were obtained for the isolated gallotannins 1,6-di-, 1,2,6-tri- and 1,2,3,6-tetra-O-galloyl-beta-D-glucose. Carob fibre was found to contain a rich variety of phenolic antioxidants. A total of 24 polyphenol compounds were identified with a yield of 3.94 g/kg (dry weight). The profile was dominated by gallic acid in various forms: free gallic acid (42% of polyphenols by weight), gallotannins (29%), and methyl gallate (1%), while simple phenols, mainly cinnamic acid, made up about 2% of the total. Flavonoids represented 26% of the polyphenols, and the major components were identified as the glycosides myricetin- and quercetin-3-O-alpha-L-rhamnoside (ca. 9% and 10%, respectively). These data indicate that carob fibre is rich in both amount and variety of phenolic antioxidant substances, and its inclusion in the diet may have chemopreventive properties.

Alterations of phospholipid concentration and species composition of the intestinal mucus barrier in ulcerative colitis: a clue to pathogenesis.

Background: Phospholipids are essential for the normal function of the intestinal mucus barrier. The objective of this study was to systematically investigate phospholipids in the intestinal mucus of humans suffering from inflammatory bowel diseases, where a barrier defect is strongly supposed to be pathogenetic. Methods: Optimal mucus recovery was first validated in healthy mice and the method was then transferred to the endoscopic acquisition of ileal and colonic mucus from 21 patients with ulcerative colitis (UC), 10 patients with Crohns disease (CD), and 29 healthy controls. Nano‐electrospray ionization tandem mass spectrometry (ESI‐MS/MS) was used to determine phosphatidylcholine (PC), lysophosphatidylcholine (LPC), and sphingomyelin (SM) in lipid extracts of mucus specimens. Results: Human and rodent mucus contained very similar phospholipid species. In the ileal and colonic mucus from patients suffering from UC, the concentration of PC was highly significantly lower (607 ± 147 pmol/100 &mgr;g protein and 745 ± 148 pmol/100 &mgr;g protein) compared to that of patients with CD (3223 ± 1519 pmol/100 &mgr;g protein and 2450 ± 431 pmol/100 &mgr;g protein) and to controls (3870 ± 760 pmol/100 &mgr;g protein and 2790 ± 354 pmol/100 &mgr;g protein); overall, P = 0.0002 for ileal specimens and P < 0.0001 for colonic specimens. Independent of disease activity, patients suffering from UC showed an increased saturation grade of PC fatty acid residues and a higher LPC‐to‐PC ratio. Conclusions: The intestinal mucus barrier of patients with UC is significantly altered concerning its phospholipid concentration and species composition. These alterations may be very important for the pathogenesis of this disease and underline new therapeutic strategies. Inflamm Bowel Dis 2009

Isolation and characterization of ellagitannins as the major polyphenolic components of Longan (Dimocarpus longan Lour) seeds

Longan (Dimocarpus longan Lour, syn. Euphoria longan Lam.) represents an important fruit in Northern Thailand and has significant economic impact. The fruit is either consumed fresh or as commercially prepared dried and canned products. The canning industry in Thailand produces considerable quantities of waste products, in particular Longan seeds. Because these seeds may be an exploitable source of natural phenolic antioxidants, it was of interest to identify, purify and quantitate the major potential antioxidant phenolics contained therein. The polyphenolic fraction from ground Longan seeds was obtained by extraction with methanol after delipidation with hexane. The hexane extract contained predominantly long-chain fatty acids with major contributions from palmitic (35%) and oleic (28%) acids. The polyphenolic fraction (80.90 g/kg dry weight) was dominated by ellagic acid (25.84 g/kg) and the known ellagitannins corilagin (13.31 g/kg), chebulagic acid (13.06 g/kg), ellagic acid 4-O-α-l-arabinofuranoside (9.93 g/kg), isomallotinic acid (8.56 g/kg) and geraniin (5.79 g/kg). Structure elucidation was performed with mass spectrometry and complete assignment of (1)H and (13)C NMR signals. The methanol extracts exhibited strong antioxidant capacities with an IC(50) of 154 μg/ml for reactive oxygen species attack on salicylic acid and 78 μg/ml for inhibition of xanthine oxidase in the hypoxanthine/xanthine oxidase assay. The extracts were less effective in the 2-deoxyguanosine assay (IC(50)=2.46 mg/ml), indicating that gallates along with ellagic acid and its congeners exert their potential antioxidant effects predominantly by precipitation of proteins such as xanthine oxidase. This was confirmed for the pure compounds gallic acid, methyl gallate, ellagic acid and corilagin.

Significantly greater antioxidant anticancer activities of 2,3-dehydrosilybin than silybin.

Silybin or silymarin extract has been used to treat liver diseases, and has now been entered into clinical trials for cancer treatment. Here, we compared antioxidant and anticancer activities between silybin and its oxidized form 2,3-dehydrosilybin (DHS). With IC50 at three-fold lower concentrations than silybin, DHS inhibited reactive oxygen species generation in glucose-glucose oxidase system and HepG2 cells. Compared with silybin, DHS elicited greater protection against H2O2-induced HepG2 cell death and galactosamine-induced liver injury in vivo. It is known that oxidants induce releases of metalloproteinases (MMP)-2,-9 which are responsible for invasive and metastasis potentials of transformed cells. DHS at 10 microM markedly inhibited MMP-2,-9 releases as well as invasiveness, while silybin at 90 microM had marginal effects. DHS but not silybin at 30 microM induced apoptosis and loss of mitochondrial membrane potentials. LD50 of DHS was five-fold lower than that of silybin. Our data suggest that DHS may be more useful therapeutically than silybin.

Biliary phosphatidylcholine and lysophosphatidylcholine profiles in sclerosing cholangitis

AIM To analyze phospholipid profiles in intrahepatic bile from patients with primary sclerosing cholangitis (PSC) and secondary sclerosing cholangitis (SSC). METHODS Intrahepatic bile specimens collected via endoscopic retrograde cholangiography from 41 patients were analyzed. Fourteen of these patients were diagnosed with PSC, 10 with SSC, 11 with choledocholithiasis or no identifiable biliary disease, and 6 with cholangiocellular carcinoma (CCC). Bile acid, cholesterol, protein, and bilirubin contents as well as pancreas lipase activity in bile were determined by biochemical methods. Phosphatidylcholine (PC) and lysophosphatidylcholine (LPC) species were quantified using nano-electrospray ionization tandem mass spectrometry. RESULTS Bile from all the examined patient groups showed a remarkably similar PC and LPC species composition, with only minor statistical differences. Total biliary PC concentrations were highest in controls (8030 ± 1843 μmol/L) and lowest in patients with CCC (1969 ± 981 μmol/L) (P = 0.005, controls vs SSC and CCC, respectively, P < 0.05). LPC contents in bile were overall low (4.2% ± 1.8%). Biliary LPC/PC ratios and ratios of biliary PC to bilirubin, PC to cholesterol, PC to protein, and PC to bile acids showed no intergroup differences. CONCLUSION PC and LPC profiles being similar in patients with or without sclerosing cholangitis, these phospholipids are likely not of major pathogenetic importance in this disease group.