UHPLC-Q-Orbitrap /MS2 identification of (+)-Catechin oxidation reaction dimeric products in red wines and grape seed extracts

Polyphenols and Phenolic Glucosides in Antibacterial Twig Extracts of Naturally Occurring Salix myrsinifolia (Salisb.), S. phylicifolia (L.) and S. starkeana (Willd.) and the Cultivated Hybrid S. x pendulina (Wender.)

(1) Background: Salix species occurring in Finland have not been well studied for their antimicrobial potential, despite their frequent use for lung and stomach problems in traditional medicine. Thus, twig extracts of three species of Salix that are found naturally in Finland and one cultivated species were screened for their antimicrobial properties against human pathogenic bacteria. S. starkeana and S. x pendulina were screened for antibacterial effects for the first time. (2) Methods: An agar diffusion and a microplate method were used for the screenings. Time-kill effects were measured using a plate-count and a microplate method. A DPPH-method using a qualitative TLC-analysis was used to detect antioxidant compounds in antimicrobial extracts. Metabolites from a S. myrsinifolia extract showing good antibacterial effects were identified using UPLC/QTOF-MS. (3) Results: A methanol extract of S. starkeana was particularly active against B. cereus (MIC 625 µg/mL), and a methanol extract of S. myrsinifolia showed good activity against S. aureus and B. cereus (MIC 1250 µg/mL) and showed bactericidal effects during a 24 h incubation of B. cereus. Moreover, a decoction of S. myrsinifolia resulted in good growth inhibition against P. aeruginosa. Our UPLC/QTOF-MS results indicated that proanthocyanidins (PAs), and especially the dimer procyanidin B1 (m/z 577) and other procyanidin derivatives, including highly polymerized proanthocyanidins, were abundant in S. myrsinifolia methanol extracts. Procyanidin B1 and its monomer catechin, as well as taxifolin and p-hydroxycinnamic acid, all present in S. myrsinifolia twigs, effectively inhibited B. cereus (MIC 250 µg/mL). (4) Conclusions: This study indicates that Finnish Salix species contain an abundance of antibacterial condensed tannins, phenolic acids and other polyphenols that deserve further research for the antibacterial mechanisms of action.

Chemical Profile Determination and Quantitative Analysis of Components in Oryeong-san Using UHPLC-Q-Orbitrap-MS and UPLC-TQ-MS/MS

In this study, a method to both qualitatively and quantitively analyze the components of Oryeong-san (ORS), which is composed of five herbal medicines (Alisma orientale Juzepzuk, Polyporus umbellatus Fries, Atractylodes japonica Koidzumi, Poria cocos Wolf, and Cinnamomum cassia Presl) and is prescribed in traditional Oriental medicine practices, was established for the first time. First, ORS components were profiled using ultra-high-performance liquid chromatography/quadrupole Orbitrap mass spectrometry, and 19 compounds were clearly identified via comparison against reference standard compounds. Subsequently, a quantitative method based on ultra-high-performance liquid chromatography coupled with triple-quadrupole tandem mass spectrometry was established to simultaneously measure the identified compounds. Nineteen compounds were accurately quantified using the multiple-reaction-monitoring mode and used to analyze the sample; we confirmed that coumarin was the most abundant compound. The method was validated, achieving good linearity (R2 ≤ 0.9991), recovery (RSD, 0.11-3.15%), and precision (RSD, 0.35-9.44%). The results suggest that this method offers a strategy for accurately and effectively determining the components of ORS, and it can be used for quality assessment and management.

Investigation of the Quinone-quinone and Quinone-catechol products using 13C labeling, UPLC-Q-TOF/MS and UPLC-Q-Exactive Orbitrap/MS

Quinones are highly reactive oxidants and play an essential role in inducing quality deterioration of fruit and vegetable products. Here, a novel stable isotope-labeling approach in combination with high-resolution tandem mass spectrometry UPLC-Q-TOF/MS and UPLC-Q-Exactive Orbitrap/MS, was successfully applied in tracking quinone reaction pathways in both real wines and model reaction systems. Unexpectedly, the binding products of quinone-quinone and quinone-catechol that are not derived from either nucleophilic reaction or redox reaction were discovered and showed the significant high peak area.Self-coupling reactions of semiquinone radicals might provide a possible interpretation for the formation of quinone-quinone products, and a charge transfer reaction coupled with a complementary donor-acceptor interaction is feasibly responsible for the products with a quinone-catechol structure. These findings endow a new perspective for quinone metabolic pathway in foods.

Red wine coloration: A review of pigmented molecules, reactions, and applications

Color is one of the most distinctive qualities of red wine. Despite new knowledge in the field of pigment identification, copigmentation, and oxidation being forthcoming, there is still a large gap between the fundamental research and practical winemaking outcomes. A state-of-art review from these two aspects is, therefore, necessary. This review first introduces updated knowledge about the primary pigments in wine, with emphasis on their physicochemical properties. Then, the mechanisms of copigmentation and oxidation are elucidated in detail, along with their relative contributions to wine color. Finally, the practical effects of copigmentation and micro-oxygenation (MOX) in winemaking are summarized and discussed. In general, wine coloration is ultimately determined by the anthocyanin flavylium cation, which is greatly influenced by wine pH. In young red wine, grape-derived anthocyanins and nonanthocyanin polyphenols (as copigments) are the foundation for wine coloration. During aging and storage, anthocyanin derivatives are formed via various chemical reactions, where moderate oxidation plays a vital role, whereas copigmentation constantly decreases. The essence of wine color evolution relates to the changes of physicochemical properties of primary pigments in wine, where the hydration equilibrium gradually diminishes. In practice, the effects of copigment addition and MOX during real vinification can be viewed as somewhat controversial, considering that many studies showed different effects on wine color and pigment concentration. Universal features can be summarized but some phenomena still remain unclear and deserve further exploration.

Improved Analysis of Isomeric Polyphenol Dimers Using the 4th Dimension of Trapped Ion Mobility Spectrometry—Mass Spectrometry

Dehydrodicatechins resulting from (epi)catechin oxidation have been investigated in different foods and natural products, but they still offer some analytical challenges. The purpose of this research is to develop a method using ultra-high performance liquid chromatography coupled with trapped ion mobility spectrometry and tandem mass spectrometry (UHPLC−ESI−TIMS−QTOF−MS/MS) to improve the characterization of dehydrodicatechins from model solutions (oxidation dimers of (+)-catechin and/or (−)-epicatechin). Approximately 30 dehydrodicatechins were detected in the model solutions, including dehydrodicatechins B with β and ε-interflavanic configurations and dehydrodicatechins A with γ-configuration. A total of 11 dehydrodicatechins B, based on (−)-epicatechin, (+)-catechin, or both, were tentatively identified in a grape seed extract. All of them were of β-configuration, except for one compound that was of ε-configuration. TIMS allowed the mobility separation of chromatographically coeluted isomers including dehydrodicatechins and procyanidins with similar MS/MS fragmentation patterns that would hardly be distinguished by LC-MS/MS alone, which demonstrates the superiority of TIMS added to LC-MS/MS for these kinds of compounds. To the best of our knowledge, this is the first time that ion mobility spectrometry (IMS) was applied to the analysis of dehydrodicatechins. This method can be adapted for other natural products.