Roswitha Haubner

Isolation, structure elucidation and antioxidant potential of the major phenolic and flavonoid compounds in brined olive drupes

Because olives represent an important component of the Mediterranean diet, it is necessary to establish unequivocal identification and quantitation of the major potential antioxidant phenolic compounds they contain. The major phenolic antioxidants in two types of brined olives were isolated and purified by semi-preparative high performance liquid chromatography. Structural analysis was conducted using UV spectrophotometry, mass spectrometry and nuclear magnetic resonance spectroscopy. In particular, completely assigned 1H and 13C NMR data are presented and errors in literature data are corrected. The data show that tyrosol, hydroxytyrosol, 3-(3, 4-dihydroxyphenyl) propanoic acid (dihydrocaffeic acid), dihydro-p-coumaric acid (phloretic acid), the phenylpropanoid glucosides acteoside (verbascoside) and isoacteoside, along with the flavonoids luteolin and apigenin are major components of the phenolic fraction of brined black olives. Brined green olives contain only hydroxytyrosol and traces of other minor phenolics. Brined olives contain even higher concentrations of phenolic antioxidants than olive oil and may, therefore, be more important modulators of cancer chemopreventive activity.

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.

The occurrence of tobacco-specific nitrosamines in oral tobacco products and their potential formation under simulated gastric conditions

The levels of the tobacco-specific nitrosamines: N-nitrosoanabasine, N-nitrosoanatabine, N-nitrosonornicotine and 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone in a variety of chewing tobaccos, oral snuffs, masheri and zarda samples were determined. The potential endogenous formation of tobacco-specific nitrosamines was estimated by incubation of tobacco samples at pH 2.0 for 1 hr at 37 degrees C and over the pH range 1.0 to 5.5 under conditions simulating the normal fasting stomach, with a constant nitrite concentration of 25 microM. Under the simulated gastric conditions, N-nitrosoanabasine, N-nitrosoanatabine and N-nitrosonornicotine were formed, and maximum formation of these tobacco-specific nitrosamines occurred at pH 2.5. Nicotine, the major alkaloid present in tobacco and precursor to N-nitrosonornicotine and 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone, was not nitrosated. The formation of N-nitrosonornicotine resulted from nitrosation of nornicotine, another alkaloid also present in tobacco. Under the acidic simulated gastric conditions, slight decomposition of 4-(N-nitrosomethyl-amino)-1-(3-pyridyl)-1-butanone via transnitrosation was observed.

Pilot Walnut Intervention Study of Urolithin Bioavailability in Human Volunteers

A pilot intervention study was conducted in human volunteers (n = 4) to establish the bioavailability of urolithins, which are the terminal end-products of ellagitannin metabolism by the gastrointestinal microflora. Biospecimens (blood, feces, and urine) along with urolithins purified therefrom were analyzed for their antioxidant capacity in a range of in vitro assays. Urolithin metabolites were identified and quantitated in the biospecimens by negative ion mode HPLC-ESI-MS analysis. The data in this pilot study show that the metabolism of ellagitannins in the four volunteers gave rise to a diverse profile and a highly variable concentration of urolithins in urine. The concentration of glucuronidated urolithins in blood and urine did not correlate with antioxidant capacity. However, the antioxidant capacity of urine, but not plasma biospecimens, was highly correlated with uric acid concentration. The antioxidant capacity of fecal extracts correlated positively with the concentration of urolithin D in both the DPPH and FRAP assays, but not in the ORAC assay, which was entirely consistent with the in vitro assays for pure urolithin D.

Polyphenol Composition and Antioxidant Potential of Hibiscus esculentus L. Fruit Cultivated in Nigeria

Consumption of certain fruits and vegetables is now widely associated with chemoprevention of degenerative diseases like cancer and cardiovacsular disorders because of their antioxidant components. Polyphenols, a heterogeneous group of compounds, are one of these constituents. Hibiscus esculentus L. (Family Malvaceae), commonly referred to as okro, okra, or ladys finger, is an important component of diet in Nigeria and other countries in sub-Saharan Africa. In this article, we describe the polyphenol composition and antioxidant potential of H. esculentus of Nigerian origin. Quercetin glucoside (quercetrin) and an unidentified flavonoid were detected. In vitro antioxidant assay of methanol extract of the fruits showed potent antioxidant/radical scavenging activities with 50% inhibitory concentration values of 25 and 43 microL when analyzed by the xanthine oxidase and 2-deoxyguanosine methods, respectively. These data suggest that H. esculentus, popular especially during the rainy season in Nigeria and many tropical West, Central, and Eastern African countries, is a good contributor to the antioxidant status and disease chemoprevention of people in these countries.

Evaluation of the Polyphenol Composition and Antioxidant Activity of African Variety of Dacryodes edulis (G.Don) H.J Lam Fruit

Polyphenols are abundant micronutrients in our diet that have been credited with chemoprevention of diseases associated with oxidative stress. In this study, we investigated the whole ripened fruit of Dacryodes edulis (G.Don) H.J Lam, a multipurpose tree growing in West and Central Africa and other countries bordering the Gulf of Guinea, for polyphenol content as well as its antioxidant/radical scavenging capacity. Analysis of the methanol extract of the fruit by high-performance liquid chromatography coupled to an ultraviolet dual-array detector and mass-selective detector revealed the presence of catechol (9.27 mg/kg), gallate (10.40 mg/kg), methylgallate (0.88 mg/kg), ellagic acid (3.10 mg/kg), quercetin (0.21 mg/kg), and quercetin rhamnoside (0.76 mg/kg). The extract showed very high antioxidant potential (50% inhibitory concentration [IC(50)] = 14 microL), but a rather weak radical scavenging activity (IC(50) = 357 microL), when tested in vitro with the xanthine oxidase and 2-deoxyguanosine assay model systems, respectively. These results suggest that consumption of D. edulis could contribute to prevention of diseases that are related to oxidative stress.

Ethnobotanical survey, chemical composition, and antioxidant capacity of methanolic extract of the root bark of Annona cuneata Oliv.

The root bark of Annona cuneata Oliv. is traditionally used in the Democratic Republic of Congo to treat several debilitating conditions, such as hernia, female sterility, sexual asthenia, and parasitic infections. However, little is known about the composition of the secondary plant substances, which may contribute to these traditional medicinal effects. We conducted an ethnobotanical study and then evaluated the composition of the secondary plant substances in extracts of the root bark by using spectroscopic methods. After delipidation, the root bark was lixiviated in methanol, and components in the extract were studied by gas chromatography-mass spectometry, high-performance liquid chromatography (HPLC)-electrospray ionization-MS and nano-electrospray ionization-MS-MS. These methods identified 13 secondary plant substances (almost exclusively phenolic compounds): p-hydroxybenzaldehyde (I), vanillin (II), tyrosol (III), 3,4-dihydroxybenzaldehyde (IV), p-hydroxybenzoic acid (V), vanillyl alcohol (VI), syringaldehyde (VII), 4-hydroxy-3-methoxyphenylethanol (VIII), vanillic acid (IX), 3,4-dihydroxybenzoic acid (X), syringic acid (XI), and ferulic acid (XII), along with the phytosterol squalene (XIII). In the HPLC-based hypoxanthine/xanthine oxidase antioxidant assay system, the methanolic extract exhibited potent antioxidant capacity, with a 50% inhibitory concentration of 72 μL, equivalent to 1.38 mg/mL of raw extract. Thus, a methanol extract of A. cuneata Oliv. contained a range of polyphenolic compounds, which may be partly responsible for its known traditional medicinal effects. More detailed studies on the phytochemistry of this important plant species are therefore warranted.

Plasma 25-hydroxyvitamin D3, folate and vitamin B12 biomarkers among international colorectal cancer patients: A pilot study

Vitamin D and folate are associated with decreased colorectal cancer risk and their association with colorectal cancer prognosis is under investigation. We assessed the levels of plasma 25-hydroxyvitamin D3 (25(OH)D3), folate and vitamin B12 in an international pilot study in order to determine variability of these biomarkers based on geographical location. Plasma 25(OH)D3, folate and vitamin B12 concentrations were measured in 149 invasive, newly diagnosed colorectal cancer cases from Heidelberg (Germany), Seattle (WA, USA), and Tampa (FL, USA) and in ninety-one age- and sex-matched controls. Their associations with potential predictors were assessed using multivariate linear regression analyses. Plasma 25(OH)D3, folate and vitamin B12 concentrations differed by location. Other predictors were season for 25(OH)D3 and tumour stage (vitamin B12). Season-corrected average 25(OH)D3 concentrations were higher in Heidelberg (31·7 ng/ml; range 11·0–83·0 ng/ml) than in Seattle (23·3 ng/ml; range 4·0–80·0 ng/ml) and Tampa (21·1 ng/ml; range 4·6–51·6 ng/ml). In Heidelberg, a strong seasonal variation was observed. Folate (11·1 ng/ml) and vitamin B12 (395 pg/ml) concentrations in Heidelberg were lower than those in Seattle (25·3 ng/ml and 740 pg/ml, respectively) and Tampa (23·8 ng/ml and 522 pg/ml, respectively). Differences in plasma 25(OH)D3 and folate concentrations between Heidelberg and the US sites were observed, probably reflecting variation in outdoor activities and sun-avoidance behaviour during summer as well as in folic acid fortification and supplement use. Intra-site differences at each study location were greater than between-location variability, suggesting that individual health behaviours play a significant role. Nevertheless, the intra-site differences we observed may be due to chance because of the limited sample size. Our pilot study illustrates the value of an international cohort in studying colorectal cancer prognosis to discern geographical differences in a broad range of exposures.