Simultaneous Analysis of Six Polymethoxyflavones and Six 5‑Hydroxy-polymethoxyflavones by High Performance Liquid Chromatography Combined with Linear Ion Trap Mass Spectrometry

Polymethoxyflavones (PMFs) and monohydroxylated polymethoxyflavones (OH-PMFs) exist exclusively in the citrus genus, particularly in citrus peels. Currently, due to the broad application of PMFs and OH-PMFs in nutraceuticals, pharmaceuticals, and functional foods, their identification and quantification will be of great significance and the first criteria to meet. We have developed a validated method with high performance liquid chromatography coupled with linear ion trap mass spectrometry. The method was fully validated in linearity, precision, accuracy, and recovery. Six PMFs and their monohydroxyl counterparts, six 5-OH-PMFs, were simultaneous analyzed within 20 min for the first time. The LOD (limit of detection) and LOQ (limit of quantitation) were calculated as 0.02–0.23 and 0.05–0.76 μg/mL, respectively. The method was performed on the samples of acid treated citrus peel extracts. The citrus peel extracts with high content of PMFs and 5-OH PMFs may provide reliable and economical resources in biological activity studies and development of health beneficial products

Identification and Quantification of Potential Anti-inflammatory Hydroxycinnamic Acid Amides from Wolfberry

Wolfberry or Goji berry, the fruit of <i>Lycium barbarum</i>, exhibits health-promoting properties that leads to an extensive study of their active components. We synthesized a set of hydroxycinnamic acid amide (HCCA) compounds, including <i>trans</i>-caffeic acid, <i>trans</i>-ferulic acid, and 3,4-dihydroxyhydrocinnamic acid, with extended phenolic amine components as standards to identify and quantify the corresponding compounds from wolfberry and to investigate anti-inflammatory properties of these compounds using in vitro model. With optimized LC–MS/MS and NMR analysis, nine amide compounds were identified from the fruits. Seven of these compounds were identified in this plant for the first time. The amide compounds with a tyramine moiety were the most abundant. In vitro studies indicated that five HCCA compounds showed inhibitory effect on NO production inuded by lipopolysaccharides with IC₅₀ less than 15.08 μM (<i>trans</i>-<i>N</i>-feruloyl dopamine). These findings suggested that wolfberries demonstrated anti-inflammatory properties

Mechanism of Pyrazine Formation Intervened by Oxidized Methionines during Thermal Degradation of the Methionine–Glucose Amadori Compound

Methionine (Met) oxidation was observed during thermal degradation of methionine/glucose-derived Amadori rearrangement product (MG-ARP). The effects of oxidized methionine products, methionine sulfoxide (MetSO) and methionine sulfone (MetSO2), on pyrazine yields of the MG-ARP model were investigated. The pyrazine contents in the MG-ARP/Met and MG-ARP/MetSO models were found lower compared to those in the MG-ARP/MetSO2 model, and the inefficiency of pyrazine formation in the MG-ARP/Met model was proposed due to the fact that Met oxidation competitively inhibited the oxidation of dihydropyrazines for pyrazine formation in spite of relatively high methylglyoxal (MGO) content. The models of MGO mixed with Met, MetSO, or MetSO2 were established for further investigation of the mechanism for the involvement of Met oxidation in pyrazine formation. It was observed that the aldolization or carbonyl-amine reaction of MetSO with MGO was another important reason for the inhibition of pyrazine formation, except for the competitive inhibition of oxidative formation of MetSO on dihydropyrazine oxidation, and the adduct of MGO–MetSO was identified by MS/MS. These results also accounted for the phenomenon of low pyrazine yields but high yields of long-chain substituted pyrazines, which were converted from dihydropyrazines with the aldehyde involvement

Effect of a Labile Methyl Donor on the Transformation of 5‑Demethyltangeretin and the Related Implication on Bioactivity

Polymethoxyflavones (PMFs) belong to a subgroup of flavonoids that particularly exist in the peels of citrus fruits. Despite their many health-beneficial biofunctionalities, the lipophilic nature of PMFs limits their water solubility and oral bioavailability. To investigate the effect of the delivery system on the improvement of PMF bioavailibility, a lecithin-based emulsion was formulated for the delivery of two PMF compounds, tangeretin and 5-demethyltangeretin. While the emulsion system improved the digestion kinetics and the total solubilized PMF concentrations in in vitro lipolysis studies, the concentration of 5-demethyltangeretin decreased due to chemical transformation to its permethoxylated counterpart, tangeretin. The emulsifier lecithin used in this emulsion formulation contained a choline headgroup as a labile methyl group donor. The presence of a methyl donor potentially caused the transformation of 5-demethyltangeretin and reduced its anti-cancer-cell-proliferation activities. Moreover, this is the first report in the literature of the transformation from 5-demethyltangeretin to tangeretin in a lecithin-based emulsion during lipolysis, and the mechanism underlying this phenomenon has also been proposed for the first time

Promotion or Inhibition Effects of Exogenous Glutathione-Degraded Amino Acids on the Formation of 2,3-Butanedione and Pyrazines via Varied Pathways of Interaction with α‑Dicarbonyl Compounds Derived from <i>N</i>‑(1-Deoxy‑d‑xylulos-1-yl)-alanine

The contribution of glutathione (GSH) and free amino acids degraded from GSH to the generation of pyrazines and 2,3-butanedione was illustrated during their interaction in the thermal treatment of the Amadori compound of alanine and xylose (ARP). GSH-degraded amino acids, glutamic acid (Glu), cysteine (Cys), and glycine (Gly), but not pyroglutamic acid (pGlu), could effectively capture α-dicarbonyls to facilitate the formation of pyrazines when ARP was heated with GSH. Deoxypentosones, the precursors of 2,3-butanedione, were largely consumed in the ARP–GSH model by the interaction with GSH and its degradative Cys compared with the ARP model. The addition of GSH and deoxypentosones inhibited the further degradation of deoxypentosones, resulting in less formation of 2,3-butanedione and other α-dicarbonyl compounds. Meanwhile, the reaction between GSH-degraded Cys and deoxypentosones to form sulfur-containing compounds such as thiols accelerated the consumption of deoxypentosones; thereby, the formation of 2,3-butanedione was severely interfered. However, this inhibition was compensated for by the GSH-degraded Gly through the addition between Gly and MGO and the subsequent deamination. The involvement of exogenous GSH could simultaneously boost the yields of 2,3-butanedione and pyrazines compared with those of ARP heated alone. As the degree of GSH degradation strengthened in the ARP-thermal-degraded GSH models, the yields of both pyrazines and 2,3-butanedione steadily increased

Comprehensive applications of metabolomics on tea science and technology: opportunities, hurdles, and perspectives

With the development of metabolomics analytical techniques, relevant studies have increased in recent decades. The procedures of metabolomics analysis mainly include sample preparation, data acquisition and pre-processing, multivariate statistical analysis, as well as maker compounds’ identification. In the present review, we summarized the published articles of tea metabolomics regarding different analytical tools, such as mass spectrometry, nuclear magnetic resonance, ultraviolet–visible spectrometry, and Fourier transform infrared spectrometry. The metabolite variation of fresh tea leaves with different treatments, such as biotic/abiotic stress, horticultural measures, and nutritional supplies was reviewed. Furthermore, the changes of chemical composition of processed tea samples under different processing technologies were also profiled. Since the identification of critical or marker metabolites is a complicated task, we also discussed the procedure of metabolite identification to clarify the importance of omics data analysis. The present review provides a workflow diagram for tea metabolomics research and also the perspectives of related studies in the future</p

Competitive Formation of 2,3-Butanedione and Pyrazines through Intervention of Added Cysteine during Thermal Processing of Alanine-Xylose Amadori Compounds

The intervention of cysteine (Cys) on the formation of 2,3-butanedione and pyrazines was evaluated during the thermal processing of the alanine-xylose Amadori compound (AX-ARP). With the involvement of Cys, the competitive formation of 2,3-butanedione and pyrazines was induced. The formation of 2,3-butanedione in the AX-ARP/Cys model was suppressed due to the inhibitory effect of the precursors of 2,3-butanedione like deoxypentosones, while the added Cys in the AX-ARP/Cys model competed with the recovered alanine (Ala) to capture glyoxal and methylglyoxal to make up for the absence of pyrazines in the AX-ARP model at an initial pH value of 7. The content of pyrazines increased from 0 up to 16.48 μg/L (120 °C, 120 min). Exogenous Cys itself showed lower reactivity with 2,3-butanedione through the Strecker degradation reaction; while the pH was increased to 8, the degradative products of Cys were facilitated to consume the residual 2,3-butanedione giving rise to the formation of 2,4,5-trimethylthiazole at 120 °C. It was the degradative products of Cys that accelerated the reaction for consumption of 2,3-butanedione rather than Cys itself. Additionally, the inhibitory effect of Cys on 2,3-butanedione formation was weakened under a basic condition, while the promotional effect on the formation of pyrazines was further boosted. With more Cys participating in the process of AX-ARP thermal degradation, the formation of 2,3-butanedione was further inhibited, while the yields of pyrazines were increased

Supplementary Figures and Table from Effects of thermal treatments on 10 major phenolics and their antioxidant contributions in <i>Acer truncatum</i> leaves and flowers

This study aimed to investigate effects of thermal treatments on major phenolics and their antioxidant contributions in <i>Acer truncatum</i> leaves and flowers (ATL and ATF, respectively). With UPLC-DAD-QTOF-MS/MS, phenolic compositions of ATF were first characterized and compared with those of ATL. An optimized HPLC fingerprint was then established, and 10 major phenolics existing in both ATL and ATF were quantified. Gallic acid derivatives and flavonol-3-<i>O</i>-glycosides were found to be their dominant phenolic constituents, with the former being key constituents which was affected by thermal treatments and further influencing the variations of total phenols. Moreover, mechanism underlining the changes of phenolics in ATL and ATF by the treatments was characterized as thermolhydrolysis process. During thermal treatments, polymerized gallotannins were hydrolysed to 1,2,3,4,6-pentakis-<i>O</i>-galloyl-β-d-glucose, ethyl gallate and gallic acid, resulting in more than fivefold and twofold increase of their contents in ATL and ATF, respectively. By contrast, contents and antioxidant contributions of flavonol-3-<i>O</i>-glycosides gradually decreased during the process. Overall, this is the first report on the effects of thermal treatments on phenolics and their antioxidant contributions in ATL and ATF, and the three gallic acid derivatives with potentially higher bioactivity could be efficiently achieved by thermal treatments

Garcinol from <i>Garcinia indica</i> Downregulates Cancer Stem-like Cell Biomarker ALDH1A1 in Nonsmall Cell Lung Cancer A549 Cells through DDIT3 Activation

Nonsmall cell lung cancer (NSCLC) is the predominant type of lung cancer. Patients with NSCLC show high mortality rates because of failure to clean up cancer stem cells (CSCs). The anticancer activity of phytochemical garcinol has been identified in various cancer cell models. However, the effect of garcinol on NSCLC cell lines is still lacking. Of the NSCLC cell lines we tested, A549 cells were the most sensitive to garcinol. Interestingly, Aldehyde Dehydrogenase 1 Family Member A1 (ALDH1A1) was preferentially expressed in A549 cells and downregulated by the addition of garcinol. We also found that garcinol enriched DNA damage-inducible transcript 3 (DDIT3) and then altered DDIT3-CCAAT-enhancer-binding proteins beta (C/EBPβ) interaction resulting in a decreased binding of C/EBPβ to the endogenous ALDH1A1 promoter. Furthermore, garcinol’s inhibition of ALDH1A1 was identified in a xenograft mice model. Garcinol repressed ALDH1A1 transcription in A549 cells through alterations in the interaction between DDIT3 and C/EBPβ. Garcinol could be a potential dietary phytochemical candidate for NSCLCs patients whose tumors harbored high ALDH1A1 expression

Formation of Volatile Pyrazinones in the Asparagine Maillard Reaction Systems and Novel Pyrazinone Formation Pathways in the Amidated-Alanine Maillard Reaction Systems

Maillard reaction (MR) plays a pivotal role in the food flavor industry, including a cascade of reactions starting with the reaction between amino compounds and reducing sugars, and thus provides various colors and flavors. A new group of volatile compounds called pyrazinones found in MR are now getting more attention. In this study, eight volatile pyrazinones were found in the asparagine MR systems, in which 3,5-dimethyl- and 3,6-dimethyl-2(1H)-pyrazinones were reported for the first time. The major formation pathways were the reactions between asparagine and α-dicarbonyls, with decarboxylation as a critical step. Besides, novel alternative pathways involving alanine amidation and successive reactions with α-dicarbonyls were explored and successfully formed eight pyrazinones. The major differences between alanine-amidated pathways and decarboxylation pathways are the amidation step and absence of the decarboxylation step. For the alanine-amidated pathways, the higher the temperature, the better the amidation effect. The optimal amidation temperature was 200 °C in this study. The reaction between the alanine amide and α-dicarbonyls after amidation can happen at low temperatures, such as 35 and 50 °C, proposing the possibility of pyrazinone formation in real food systems. Further investigations should be conducted to investigate volatile pyrazinones in various food systems as well as the biological effects and kinetic formation differences of the volatile pyrazinones