Material Basis Elucidation and Quantification of Dandelion through Spectrum–Effect Relationship Study between UHPLC Fingerprint and Antioxidant Activity via Multivariate Statistical Analysis

The excessive expression of reactive oxygen species is closely connected to many diseases. Considerable studies have demonstrated dandelion as well as its ingredients exhibited antioxidant activity. However, specific material basis reflecting the antioxidant activity has not been comprehensively investigated. In this study, a spectrum–effect relationship study on dandelion between fingerprinting and antioxidant activity was analyzed in detail, while a UHPLC quantification method developed and completely validated for simultaneous determination of active ingredients in dandelion. With the establishment of dandelion fingerprints of different regions, 24 common peaks were characterized. The classic FRAP method and ABTS methods were then used to detect their antioxidant activity. Partial least squares regression analysis, bivariate correlation analysis and grey correlation method were used to accomplish the spectrum–effect relationship. Eventually, the ingredients with antioxidant activity which could be considered as candidate quality markers of dandelion were discovered through spectrum–effect relationship analysis. The six compounds including caftaric acid, chlorogenic acid, caffeic acid, chicoric acid, isochlorogenic acid A, and isochlorogenic acid C were quantitatively determined. The developed UHPLC assay method was accurate, precise, and reliable. The study has elucidated the antioxidant material basis of dandelion and provided a scientific basis for the quality control of dandelion.     

Screening of analgesic and anti‐inflammatory active component in Fructus Alpiniae zerumbet based on spectrum–effect relationship and GC–MS

Fructus Alpiniae zerumbet is widely used in Guizhou province as a miao folk herb with anti‐inflammatory, analgesic, protection against cardiovascular diseases, antihypertension and antioxidant activities. To further investigate the chemical material basis, the spectrum–effect relationship was established using gray relational analysis between the chromatographic fingerprint and its bioactivities. Herein, the fingerprints of essential oils from Fructus Alpiniae zerumbet (EOFAZ) from various sources were determined by gas chromatography mass spectrometry, and the analgesic and anti‐inflammatory bioactivities were investigated using the mouse model of acetic acid‐induced writhing test and dimethylbenzene‐induced mouse ear edema test. Finally, 17 common peaks were identified from nine batches of A. zerumbet, by comparison with the standard mass spectra in Nist2005, Wiley275 library. Meanwhile, the results showed significant analgesic and anti‐inflammatory effects in all of the different sources of EOFAZ. In particularly, peak 1 (α‐pipene), peak 3 (β‐pinene), peak 9 (camphor) and peak 16 (α‐cadinol) might be the main bioactive ingredients for analgesic and anti‐inflammatory activities. The model of the spectrum–effect relationships of EOFAZ was successfully discovered, which provided a novel platform for finding the bioactive components, a theoretical foundation for its further study and helping to establish quality control of Fructus A. zerumbet.     

Comparative study on the antioxidant activities of extracts of Coreopsis tinctoria flowering tops from Kunlun Mountains,Xinjiang, north-western China

Coreopsis tinctoria flowering tops (CTFs) from the Kunlun Mountains in Xinjing (north-western China) have been used for tea production for about a century. This study aims to assess the antioxidant activities and total phenolic, flavonoid and proanthocyanidin contents of various solvent extracts of CTF. CTF was extracted using n-hexane, chloroform, ethyl acetate, n-butanol, 75% aqueous ethanol (AEE) and water. The antioxidant activities of the CTF extracts were investigated through DPPH, ABTS, ^*OH, ^*O₂^? , total antioxidant capacity and reducing power assays. The results showed that n-butanol extract showed the highest contents of total phenols and flavonoids, with DPPH, ABTS and ^*OH radical-scavenging activities with IC₅₀ values of 134, 90.72 and 13.8 μg mL^? 1, respectively. The AEE demonstrated the strongest DPPH and ABTS radical-scavenging activities, with IC₅₀ values of 103 and 75.16 μg mL^? 1, respectively. Given its high antioxidant effect, CTF is a good source of natural antioxidants or functional food materials.     

Screening of Potential Thrombin and Factor Xa Inhibitors from the Danshen–Chuanxiong Herbal Pair through a Spectrum–Effect Relationship Analysis

In this study; a spectrum–effect relationship analysis combined with a high-performance liquid chromatography–mass spectrometry (LC–MS) analysis was established to screen and identify active components that can inhibit thrombin and factor Xa (THR and FXa) in Salviae Miltiorrhizae Radix et Rhizoma–Chuanxiong Rhizoma (Danshen–Chuanxiong) herbal pair. Ten potential active compounds were predicted through a canonical correlation analysis (CCA), and eight of them were tentatively identified through an LC–MS analysis. Furthermore; the enzyme inhibitory activity of six available compounds; chlorogenic acid; Z-ligustilide; caffeic acid; ferulic acid; tanshinone I and tanshinone IIA; were tested to verify the feasibility of the method. Among them; chlorogenic acid was validated to possess a good THR inhibitory activity with IC₅₀ of 185.08 µM. Tanshinone I and tanshinone IIA are potential FXa inhibitors with IC₅₀ of 112.59 µM and 138.19 µM; respectively. Meanwhile; molecular docking results show that tanshinone I and tanshinone IIA; which both have binding energies of less than −7.0 kcal·mol⁻¹; can interact with FXa by forming H-bonds with residues of SER214; GLY219 and GLN192. In short; the THR and FXa inhibitors in the Danshen–Chuanxiong herbal pair have been successfully characterized through a spectrum–effect relationship analysis and an LC–MS analysis.     

Structure–activity relationship of N‐heterocyclic carbene–Pd(II)–imidazole complexes in Suzuki–Miyaura coupling between 4‐methoxyphenyl chloride and phenylboronic acid

A series of N‐heterocyclic carbene–PdCl₂–imidazole [NHC–Pd(II)–Im] complexes were synthesized and the structure of most of them was unambiguously determined by X‐ray single‐crystal diffraction. The structure–activity relationship of these complexes was investigated for the Suzuki–Miyaura coupling between 4‐methoxyphenyl chloride and phenylboronic acid, and the effect of the NHCs and Im moieties were fully discussed. The sterically hindered IPr‐based complex showed the highest catalytic activity. Copyright © 2013 John Wiley & Sons, Ltd.     

Phosphorus‐based Schiff bases and their complexes as nontoxic antioxidants: Structure–activity relationship and mechanism of action

Phosphorus‐based Schiff base were synthesized by treating bis{3‐[2‐(4‐amino‐1.5‐dimethyl‐2‐phenyl‐pyrazol‐3‐ylideneamino)ethyl]‐indol‐1‐ylmethyl}‐phosphinic acid with paraformaldehyde and characterized as a novel antioxidant. Its corresponding complexes [(VO)₂L(SO₄)₂], [Ni₂LCl₄], [Co₂LCl₄], [Cu₂LCl₄], [Zn₂LCl₄], [Cd₂LCl₄], [Hg₂LCl₄], [Pd₂LCl₄], and [PtLCl]Cl₂ were analyzed by Fourier transform‐infrared, (¹H and ¹³C) nuclear magnetic resonance, and mass and UV–Vis spectroscopy. Experimental data showed that the ligand coordinated with the metal ions via donor atoms such as nitrogen to form an octahedral arrangement of the Schiff base around the central transition‐metal atom. The nature of these complexes was identified using the molar ratio and Job's methods, with the results agreeing with a metal‐to‐ligand (M:L) molar ratio of 2:1, expect for Pt, whose M:L was 1:1. Thermodynamic activation parameters such as ?E*, ?H*, ?S*, ?G*, and K were determined from the thermogravimetric analysis curve using the Coats–Redfern method. The antioxidant activities of the prepared compounds were assessed by using 1.1‐diphenyl‐2‐picrylhydrazyl as the free radical, and the results show that the complex Schiff bases were found to possess potent antioxidant activity. The structure–activity relationship of the ligand and its complexes indicates that the presence of electron‐donating moieties, such as Co(II) and Ni(II), in the chemical structure increases the antioxidant activity, whereas the Pt(IV) and Pd(II) complexes diminished the antioxidant activity, indicating the superior activity of the hydroxyl radical (OH^·) over the superoxide radical.     

Specific Deuteration in Patuletin and Related Flavonoids via Keto–Enol Tautomerism: Solvent‐ and Temperature‐Dependent 1H‐NMR Studies

An H/D exchange process in patuletin ( 1 ) and its derivatives in D‐donor solvents (e.g., CF₃COOD), which occurs regioselectively at C(8) was observed for the first time during NMR studies. The effect of substituents and temperature on the deuteration of various flavonoids (see Fig. 1) which include apigenin, chrysin, galangin, kaempferol, luteolin, morin, myricetin, patuletin, patulitrin, and quercetin, as well as derivatives of patuletin was examined extensively under NMR conditions. The rate constant of deuteration at C(8) of patuletin ( 1 ) and two flavones, luteolin ( 3 ) and apigenin ( 12 ), was also determined in CF₃COOD. The D‐atom was introduced into the flavonoids via a keto–enol tautomerism (Scheme 1). During these studies, monodeuterated patuletin was also obtained as a new compound. The examined flavonoids have been reported to possess significant pharmacological activities, and their deuterated derivatives would be of importance for the identification and quantification of these compounds in biological matrices.     

Stereoselective synthesis of procyanidin B3-3-O-gallate and 3,3″-di-O-gallate, and their abilities as antioxidant and DNA polymerase inhibitor

A simple method for the synthesis of procyanidin B3 substituted with a galloyl group at the 3 and 3″ position is described. Condensation of a benzylated catechin-3-O-gallate electrophile with a nucleophile, catechin and catechin-3-O-gallate, proceeded smoothly and stereoselectively to afford the corresponding dimer gallates, procyanidin B3-3-O-gallate and procyanidin B3-3,3″-di-O-gallate, in good yields. Further, their antioxidant activities on UV-induced lipid peroxide formation, DPPH radical scavenging activity and inhibitory activity of DNA polymerase were also investigated. Among three procyanidin B3 congeners (procyanidin B3, 3-O-gallate and 3,3″-di-O-gallate), the 3,3″-di-O-gallate derivative showed the strongest antioxidant and radical scavenging activity. Interestingly, the 3-O-gallate derivative was the strongest inhibitor of mammalian DNA polymerase with IC₅₀ value of 0.26 μM, although it showed the weakest antioxidant and radical scavenging activity. It became apparent that the presence of a galloyl group at the C-3 position in the proanthocyanidin oligomer was very important for biological activity, however, the antioxidant activity of these compounds was not parallel to the DNA polymerase inhibitory activity.     

Effects of Centella asiatica extract on antioxidant status and liver metabolome of rotenone‐treated rats using GC–MS

Centella asiatica has been used as a culinary vegetable or medicinal herb. In this study, the hepatoprotective effect of the standardized extract of C. asiatica (ECa233) in rotenone‐treated rats was examined using a GC–MS‐based metabolomic approach. ECa233 contains >80% triterpenoids with a ratio of madecassoside to asiaticoside of 1.5(±0.5):1. Rats were randomly divided into three groups (with six rats/group): sham negative control, rotenone positive control and the ECa233 test group. Rats in the ECa233 group received 10 mg/kg ECa233 orally for 20 days, followed by 2.5 mg/kg intraperitoneal rotenone injection to induce toxicity before being sacrificed. Metabolomic analysis showed that supplementation of ECa233 protected rat liver against rotenone toxicity. Pipecolinic acid was one of the most important metabolites; its level was decreased in the rotenone group as compared with the control. Supplementation with ECa233 before administration of rotenone raised pipecolinic acid to levels intermediate between controls and rotenone alone. The metabolomics approach also helped discover a possible new genuine epimetabolite in the present work. Antioxidant tests revealed that ECa233 inhibited lipid peroxidation and increased catalase activities in liver tissue.     

Determination of phenolic compounds by MALDI–TOF and essential oil composition by GC–MS during three development stages of Origanum majorana L.

This study aimed to investigate the effect of the maturation process of sweet marjoram (Origanum majorana L.) on essential oil composition, the phenolic profile of ethanolic extract and their antioxidant capacities. The essential oil composition was studied at three stages of maturity by GC–MS. Thirty compounds were detected representing 100% of the total essential oil. p‐Menth‐1‐en‐4‐ol was the major compound (37.15–76.94%) followed by cyclohexanol‐3,3,5 trimethyl (5.41–15.99%) and α‐terpineol (0.94–11.34%). During the maturation process, an accumulation of oxygenated monoterpenes was observed. The phenolic composition was studied using matrix‐assisted laser desorption/ionization time of flight. The analysis showed the presence of short flavonoid monomers at all stages of maturation. The antioxidant capacity of ethanolic extracts and essential oils was evaluated using the DPPH assay, iron chelating power and reducing power assay. The highest phenolic content and antioxidant capacity were found at flowering stage. These findings on essential oil composition, phenolic profile and antioxidant capacity of O. majorana at three different stages of development provide more information on how these secondary metabolites are accumulated.     

Tracing novel hemostatic compounds from heating products of total flavonoids in Flos Sophorae by spectrum–effect relationships and column chromatography

Flos Sophorae and its processed product have been clinically used to treat hemorrhage. In this study, the total ion chromatographic fingerprints of the heating products of total flavonoids in Flos Sophorae were established by high‐performance liquid chromatography with tandem mass spectrometry and the hemostatic activities were studied by hemostatic screening tests in vivo. The spectrum–effect relationships between fingerprints and hemostatic activities were investigated using canonical correlation analysis to trace the peaks responsible for the hemostatic effects. The predicted active peaks in fingerprints were isolated by column chromatography and their structures were identified by NMR spectroscopy and mass spectrometry. The hemostatic activities of them were verified by platelet aggregation and procoagulation assays in vitro. Canonical correlation analysis results showed that peak 8 and peak 11 were correlated most closely, thus probably being the main hemostatic compounds. Through column chromatography separation, peak 8 (compound I) and peak 11 (compound II) were obtained with purities of 95.61 and 93.38%, respectively, and were discovered new hemostatic compounds named as huaicarbon A (I) and huaicarbon B (II), respectively. This study provides a universal model to trace the active compounds of other herbs which have bioactivity enhancement after processing by spectrum–effect relationships and column chromatography.     

Screening bioactive quality control markers of QiShenYiQi dripping pills based on the relationship between the ultra‐high performance liquid chromatography fingerprint and vascular protective activity

Traditional Chinese medicine consists of complex phytochemical constituents. Selecting appropriate analytical markers of traditional Chinese medicine is a critical step in quality control. Currently, the combination of fingerprinting and efficacy evaluation is considered as a useful method for screening active ingredients in complex mixtures. This study was designed to develop an orthogonal partial least squares model for screening bioactive quality control markers of QishenYiqi dripping pills based on the fingerprint–efficacy relationship. First, the chemical fingerprints of 49 batches of QishenYiqi dripping pill samples were established by ultra‐high performance liquid chromatography coupled with a photodiode array detector. Second, ultra‐high performance liquid chromatography coupled with quadrupole‐time‐of‐flight mass spectrometry was exploited to systematically investigate the 36 copossessing fingerprint components in QishenYiqi dripping pills. The vascular protective activity of QishenYiqi dripping pills was determined by using a cell counting kit‐8 assay. Finally, fingerprint–efficacy relationship was established by orthogonal partial least squares model. The results indicated that ten components exhibited strong correlation with vascular protective activity, and these were preliminarily screened as quality control markers. The present study provided a novel idea for the study of the pharmacodynamic material basis and quality evaluation of QishenYiqi dripping pills.     

Assessment and acceleration of binding energy calculations for protein–ligand complexes by the fragment molecular orbital method

In the field of drug discovery, it is important to accurately predict the binding affinities between target proteins and drug applicant molecules. Many of the computational methods available for evaluating binding affinities have adopted molecular mechanics‐based force fields, although they cannot fully describe protein–ligand interactions. A noteworthy computational method in development involves large‐scale electronic structure calculations. Fragment molecular orbital (FMO) method, which is one of such large‐scale calculation techniques, is applied in this study for calculating the binding energies between proteins and ligands. By testing the effects of specific FMO calculation conditions (including fragmentation size, basis sets, electron correlation, exchange‐correlation functionals, and solvation effects) on the binding energies of the FK506‐binding protein and 10 ligand complex molecule, we have found that the standard FMO calculation condition, FMO2‐MP2/6‐31G(d), is suitable for evaluating the protein–ligand interactions. The correlation coefficient between the binding energies calculated with this FMO calculation condition and experimental values is determined to be R = 0.77. Based on these results, we also propose a practical scheme for predicting binding affinities by combining the FMO method with the quantitative structure–activity relationship (QSAR) model. The results of this combined method can be directly compared with experimental binding affinities. The FMO and QSAR combined scheme shows a higher correlation with experimental data (R = 0.91). Furthermore, we propose an acceleration scheme for the binding energy calculations using a multilayer FMO method focusing on the protein–ligand interaction distance. Our acceleration scheme, which uses FMO2‐HF/STO‐3G:MP2/6‐31G(d) at R_int = 7.0 Å, reduces computational costs, while maintaining accuracy in the evaluation of binding energy. © 2015 Wiley Periodicals, Inc.     

Natural Compounds against Neurodegenerative Diseases: Molecular Characterization of the Interaction of Catechins from Green Tea with Aβ1–42, PrP106–126, and Ataxin‐3 Oligomers

By combining NMR spectroscopy, transmission electron microscopy, and circular dichroism we have identified the structural determinants involved in the interaction of green tea catechins with Aβ1–42, PrP106–126, and ataxin‐3 oligomers. The data allow the elucidation of their mechanism of action, showing that the flavan‐3‐ol unit of catechins is essential for interaction. At the same time, the gallate moiety, when present, seems to increase the affinity for the target proteins. These results provide important information for the rational design of new compounds with anti‐amyloidogenic activity and/or molecular tools for the specific targeting of amyloid aggregates in vivo.     

Multicomponent quantitative analysis combined with antioxidant and alpha‐glucosidase inhibitory activities for the quality evaluation of Gastrodia elata from different regions

Gastrodia elata (G. elata), as a natural plant with nourishing and edible value, plays a vital role in food and pharmaceutical production. In the present study, a novel approach for the simultaneous determination of six components based on high‐performance liquid chromatography (HPLC) coupled with photodiode array detection (PDA) was developed for the quality evaluation of G. elata from different regions. Meanwhile, antioxidant and α‐glucosidase inhibitory activities were estimated and compared. The results indicated that the total contents of the six compounds in G. elata from Guizhou and Zhejiang provinces obtained by boiling were higher than those obtained by steaming in Anhui and Yunnan provinces. In addition, samples from Guizhou, Yunnan and Shanxi provinces contained more p‐hydroxybenzyl alcohol, and always possessed higher antioxidant activity, while samples collected from Anhui province showed the highest α‐glucosidase inhibitory activity with the highest gastrodin content. The results revealed that the quality of G. elata was affected by different regions and different initial processing technologies, which provided a reference for the selection and application of G. elata.