Quantitation of Key Antioxidants and Their Contribution to the Oxidative Stability of Beer.

A sensitive high-performance liquid chromatography-triple quadrupole mass spectrometry (HPLC-MS/MSMRM) method, leveraging both technique and internal calibration, was developed for the simultaneous and comprehensive quantitative analysis of 46 antioxidants and antioxidant precursors in different beer types without any cleanup procedure. Combined with their in vitro antioxidant activity, a dose-activity estimation exposed a group of 10 key antioxidants, namely, tryptophan, tyrosine, hordatine A, hordatine B, procyanidin B3, prodelphinidin B3, tachioside (3-methoxy-4-hydroxyphenyl-ß-d-glucopyranoside), (+)-catechin, tyrosol, and ferulic acid. To study the effect of antioxidants in spiking and aging studies, another liquid chromatography-MS (LC-MS)-based method was developed, monitoring markers for oxidation in beer. A positive effect of the antioxidants on the flavor stability at naturally relevant concentrations was shown by a slowing of oxygen-dependent aging reactions highlighted in beer storage trials under oxygen atmosphere. Thereby, a doubling of the natural concentration of all investigated antioxidants in beer revealed a limit inhibition of 67% on the degradation of cis-isocohumulone to hydroxy-cis-alloisocohumulone.

Quantitative Antioxidant Profiling Throughout Beer Brewing Followed by Discovery and Isolation of Precursors from Barley (Hordeum vulgare L.).

The application of high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS) revealed the origin and evolution of antioxidants during the brewing process of hopped and unhopped reference beer. As tachioside (3-methoxy-4-hydroxyphenyl-ß-d-glucopyranoside), arbutin (4-hydroxyphenyl-ß-d-glucopyranoside), and hordatines clearly increased during the fermentation step, the raw material barley was investigated as a source of the corresponding precursors. Therefore, 4-hydroxyphenyl-ß-d-glucopyranosyl-(1 → 6)-ß-d-glucopyranosyl-(1 → 6)-ß-d-glucopyranoside, 4-hydroxy-3-methoxyphenyl-ß-d-glucopyranosyl-(1 → 6)-ß-d-glucopyranoside, 4-hydroxy-3-methoxyphenyl-ß-d-glucopyranosyl-(1 → 6)-ß-d-glucopyranosyl-(1 → 6)-ß-d-glucopyranoside, and 4-hydroxy-2-methoxyphenyl-ß-d-glucopyranosyl-(1 → 6)-ß-d-glucopyranosyl-(1 → 6)-ß-d-glucopyranoside were isolated from barley for the first time, and identified using liquid chromatography-mass spectrometry (LC-MS) and one-dimensional/two-dimensional-nuclear magnetic resonance (1D/2D-NMR) experiments. Moreover, hordatine glucosides A, B, and C were isolated and identified from barley, and hordatine C glucoside was characterized for the first time. A fermentation model followed by HPLC-MS/MS analysis substantiated the release of tachioside from 4-hydroxy-3-methoxyphenyl-ß-d-glucopyranosyl-(1 → 6)-ß-d-glucopyranoside by Saccharomyces cerevisiae. Quantitation experiments monitoring the content in wheat, barley, and different barley malt types demonstrated a wide range of concentrations, providing a basis for further comprehensive investigations to optimize the antioxidant yield in beer to contribute to improved flavor stability.

Activity-Guided Identification of in Vitro Antioxidants in Beer.

In order to locate the key antioxidants contributing to oxidative stability of beer, activity-guided fractionation in combination with the oxygen radical absorbance capacity (ORAC) assay, hydrogen peroxide scavenging (HPS) assay, and linoleic acid (LA) assay was applied to a pilsner-type beer. LC-MS and 1D/2D NMR experiments led to the identification of a total of 31 antioxidants, among which 3-methoxy-4-hydroxyphenyl-ß-d-glucopyranoside (tachioside), 4-(2-formylpyrrol-1-yl)butyric acid, 4-[2-formyl-5-(hydroxymethyl)pyrrol-1-yl]butyric acid, n-multifidol-3-O-ß-d-glucoside, quercetin-3-O-(6″-malonyl)-glucoside, 4-feruloylquinic acid, syringaresinol, saponarin, and hordatines A-C have been isolated from beer for the first time. On a molar comparison, the hordatines A-C, saponarin, and quercetin-3-O-ß-d-(6″-malonyl)glucoside were evaluated with the highest antioxidant activities of all identified beer constituents, reaching values of 10-17.5 (ORAC), 2.0-4.1 (HPS), and 1.1-6.1 µmol TE/µmol (LA) for hordatines A-C.

Bioactive compounds from Cornus officinalis fruits and their effects on diabetic nephropathy.

ETHNOPARMACOLOGICAL RELEVANCE: The fruit of Cornus officinalis, called "Shanzhuyu", a traditional medicine in China, is used for the treatment of kidney diseases, including diabetic nephropathy. The aim of this study is to investigate the anti-diabetic nephropathy activity of Shanzhuyu and the active compounds in the fruit. MATERIALS AND METHODS: The air dried fruit of Cornus officinalis was extracted in 80% EtOH, the obtained residue was fractioned on D101 resin column eluted with H2O/EtOH solution to get five crude fractions (fr. A-E). The anti-diabetic nephropathy activity of fractions (fr. A-E) was evaluated in vitro by inhibiting the expression of collagen IV (Col V), fibronectin (FN) and IL-6 in high-glucose-induced mesangial cells. By preliminary bio-assay screenings, repeated column chromatography on fraction B-D led the isolation of 22 compounds, whose structures were determined by extensive spectroscopic analysis, and the anti-diabetic nephropathy activity of the isolated compounds was also evaluated. RESULTS: Two new iridoid glucosides, logmalicids A and B (1 and 2), together with 20 known compounds (3-22) were isolated from the extract of Shanzhuyu under the bioassay-guided screenings. The anti-diabetic nephropathy activity assay displayed that fractions A, D and E could significantly inhibit the production of Col IV; fractions A and C could significantly inhibit the expression of FN and IL-6 in the high-glucose-stimulated mesangial cells at concentration of 50 µg/mL; and loganin (3) and its derivatives (1 and 2) could significantly inhibit the expression of FN and IL-6 at concentration of 10 µM, respectively. CONCLUSIONS: The results suggested that loganin and its derivatives were the active compounds in Cornus officinalis fruit (Shanzhuyu) on diabetic nephropathy. This study further supported the traditional use of Shanzhuyu to treat diabetic nephropathy and related kidney diseases.