Pei Chen

UHPLC-PDA-ESI/HRMS/MS(n) analysis of anthocyanins, flavonol glycosides, and hydroxycinnamic acid derivatives in red mustard greens (Brassica juncea Coss variety).

An UHPLC-PDA-ESI/HRMS/MS(n) profiling method was used for a comprehensive study of the phenolic components of red mustard greens ( Brassica juncea Coss variety) and identified 67 anthocyanins, 102 flavonol glycosides, and 40 hydroxycinnamic acid derivatives. The glycosylation patterns of the flavonoids were assigned on the basis of direct comparison of the parent flavonoid glycosides with reference compounds. The putative identifications were obtained from tandem mass data analysis and confirmed by the retention time, elution order, and UV-vis and high-resolution mass spectra. Further identifications were made by comparing the UHPLC-PDA-ESI/HRMS/MS(n) data with those of reference compounds in the polyphenol database and in the literature. Twenty-seven acylated cyanidin 3-sophoroside-5-diglucosides, 24 acylated cyanidin 3-sophoroside-5-glucosides, 3 acylated cyanidin triglucoside-5-glucosides, 37 flavonol glycosides, and 10 hydroxycinnamic acid derivatives were detected for the first time in brassica vegetables. At least 50 of them are reported for the first time in any plant materials.

Chromatographic profiles and identification of new phenolic components of Ginkgo biloba leaves and selected products.

Ginkgo biloba leaves and their extracts are one of the most widely used herbal products and/or dietary supplements in the world. A systematic study of the phenolic compounds is necessary to establish quality parameters. A modified LC-DAD-ESI/MS method was used to obtain chromatographic profiles for the flavonoids and terpene lactones of Ginkgo biloba leaves. The method was used to identify 45 glycosylated flavonols and flavones, 3 flavonol aglycones, catechin, 10 biflavones, a dihydroxybenzoic acid, and 4 terpene lactones in an aqueous methanol extract of the leaves. The extracted G. biloba leaf products contained the same flavonoids as the raw leaves except for the lack of biflavones. The detected glycosylated flavonol contents were equal to or more than 0.0008% of the dry plant material. This is the first report of the presence of more than 20 of these flavonoids in G. biloba.

Chemical Composition of Five Commercial Gynostemma pentaphyllum Samples and Their Radical Scavenging, Antiproliferative, and Anti-inflammatory Properties

Five Gynostemma pentaphyllum (GP) samples were investigated and compared for their chemical compositions and their antioxidant, antiproliferative, and anti-inflammatory effects. Extracts (50% acetone, 75% ethanol, and 100% ethanol) of the five GP samples (GP1-5) differed in their total phenolic, saponin, and flavonoid contents and in their rutin and quercetin concentrations. The highest level of total flavonoids was 63.5 mg of rutin equiv/g in GP4, and the greatest total phenolic content was 44.3 mg of gallic acid equiv/g in GP1 with 50% acetone as the extraction solvent. GP2 had the highest total saponin content of 132.6 mg/g with 100% ethanol as the extraction solvent. These extracts also differed in their scavenging capacity against DPPH and hydroxyl radicals, although they all showed significant radical scavenging capacity. The 100% ethanol extracts also showed dose-dependently strong inhibition on IL-6 and Ptgs2 mRNA expression and weak inhibition on TNF-α mRNA expression. In addition, GP1 had the highest antiproliferative activity at 3.2 mg equiv/mL concentration in HT-29 human colon cancer cells. The results from this study will be used to promote the application of G. pentaphyllum for improving human health.

UHPLC-PDA-ESI/HRMSn profiling method to identify and quantify oligomeric proanthocyanidins in plant products.

Oligomeric proanthocyanidins were successfully identified by UHPLC-PDA-HRMSn in a selection of plant-derived materials (jujube fruit, Fuji apple, fruit pericarps of litchi and mangosteen, dark chocolate, and grape seed and cranberry extracts). The identities of 247 proanthocyanidins were theoretically predicted by computing high-accuracy masses based on the degree of polymerization, flavan-3-ol components, and the number of A type linkages and galloyls. MSn fragments allowed characterization on flavan-3-ol based on the monomer, connectivity, and location of A-type bonds. Identification of doubly or triply charged ions of 50 PAs was made on the basis of theoretical calculations. A single catechin standard and molar relative response factors (MRRFs) were used to quantify the well-separated PAs. The ratios of the SIM peak counts were used to quantify each of the unseparated isomers. This is the first report of direct determination of each of the proanthocyanidins in plant-derived foods and proanthocyanidins containing an epifisetinidol unit in grape seeds.

Profiling Polyphenols in Five Brassica species Microgreens by UHPLC-PDA-ESI/HRMSn

Brassica vegetables are known to contain relatively high concentrations of bioactive compounds associated with human health. A comprehensive profiling of polyphenols from five Brassica species microgreens was conducted using ultrahigh-performance liquid chromatography photodiode array high-resolution multistage mass spectrometry (UHPLC-PDA-ESI/HRMS(n)). A total of 164 polyphenols including 30 anthocyanins, 105 flavonol glycosides, and 29 hydroxycinnamic acid and hydroxybenzoic acid derivatives were putatively identified.The putative identifications were based on UHPLC-HRMS(n) analysis using retention times, elution orders, UV-vis and high-resolution mass spectra, and an in-house polyphenol database as well as literature comparisons. This study showed that these five Brassica species microgreens could be considered as good sources of food polyphenols.

Flow Injection Mass Spectral Fingerprints Demonstrate Chemical Differences in Rio Red Grapefruit with Respect to Year, Harvest Time, and Conventional versus Organic Farming

Spectral fingerprints were acquired for Rio Red grapefruit using flow injection electrospray ionization with ion trap and time-of-flight mass spectrometry (FI-ESI-IT-MS and FI-ESI-TOF-MS). Rio Red grapefruits were harvested 3 times a year (early, mid, and late harvests) in 2005 and 2006 from conventionally and organically grown trees. Data analysis using analysis of variance principal component analysis (ANOVA-PCA) demonstrated that, for both MS systems, the chemical patterns were different as a function of farming mode (conventional vs organic), as well as growing year and time of harvest. This was visually obvious with PCA and was shown to be statistically significant using ANOVA. The spectral fingerprints provided a more inclusive view of the chemical composition of the grapefruit and extended previous conclusions regarding the chemical differences between conventionally and organically grown Rio Red grapefruit.

Authentication of Organically and Conventionally Grown Basils by Gas Chromatography/Mass Spectrometry Chemical Profiles

Basil plants cultivated by organic and conventional farming practices were accurately classified by pattern recognition of gas chromatography/mass spectrometry (GC/MS) data. A novel extraction procedure was devised to extract characteristic compounds from ground basil powders. Two in-house fuzzy classifiers, i.e., the fuzzy rule-building expert system (FuRES) and the fuzzy optimal associative memory (FOAM) for the first time, were used to build classification models. Two crisp classifiers, i.e., soft independent modeling by class analogy (SIMCA) and the partial least-squares discriminant analysis (PLS-DA), were used as control methods. Prior to data processing, baseline correction and retention time alignment were performed. Classifiers were built with the two-way data sets, the total ion chromatogram representation of data sets, and the total mass spectrum representation of data sets, separately. Bootstrapped Latin partition (BLP) was used as an unbiased evaluation of the classifiers. By using two-way data sets, average classification rates with FuRES, FOAM, SIMCA, and PLS-DA were 100 ± 0%, 94.4 ± 0.4%, 93.3 ± 0.4%, and 100 ± 0%, respectively, for 100 independent evaluations. The established classifiers were used to classify a new validation set collected 2.5 months later with no parametric changes except that the training set and validation set were individually mean-centered. For the new two-way validation set, classification rates with FuRES, FOAM, SIMCA, and PLS-DA were 100%, 93%, 97%, and 100%, respectively. Thereby, the GC/MS analysis was demonstrated as a viable approach for organic basil authentication. It is the first time that a FOAM has been applied to classification. A novel baseline correction method was used also for the first time. The FuRES and the FOAM are demonstrated as powerful tools for modeling and classifying GC/MS data of complex samples, and the data pretreatments are demonstrated to be useful to improve the performance of classifiers.

Classification of Cultivation Locations of Panax quinquefolius L Samples using High Performance Liquid Chromatography Electrospray Ionization Mass Spectrometry and Chemometric Analysis

Panax quinquefolius L ( P. quinquefolius L) samples grown in the United States and China were analyzed with high performance liquid chromatography-mass spectrometry (HPLC-MS). Prior to classification, the two-way data sets were subjected to pretreatment including baseline correction and retention time (RT) alignment. Principal component analysis (PCA) and projected difference resolution (PDR) metrics were used to evaluate the data quality and the pretreatment effects. A fuzzy rule-building expert system (FuRES) classifier was used to classify the P. quinquefolius L samples grown in the United States and China with the optimized partial least-squares (o-PLS) classifier as the positively biased control method. A classification rate as high as 98 ± 3% with FuRES was obtained after baseline correction and RT alignment, which is equivalent to the result obtained by using the positively biased o-PLS control method (98 ± 3%). RT alignment improved the classification rates for both FuRES and o-PLS classifiers (18% improvement for the FuRES classification rate and 10% improvement for the o-PLS classification rate with baseline correction). From the rule obtained to classify the P. quinquefolius L samples grown in the United States and China, peaks were identified that can be prospective biomarkers for differentiating samples from different growth regions. HPLC-MS with chemometric analysis has the potential to be used as an authentication method for P. quinquefolius L grown in China and the United States.

A flow-injection mass spectrometry fingerprinting method for authentication and quality assessment of Scutellaria lateriflora-based dietary supplements

Scutellaria lateriflora, commonly known as skullcap, is used as an ingredient in numerous herbal products. However, it has been occasionally adulterated/contaminated with Teucrium canadense and/or Teucrium chamaedrys, commonly known as germander, due to the morphological similarities between the two genera. The latter contains hepatotoxic diterpenes. Despite the potential hepatotoxicity introduced by germander contamination, analytical methodologies for the authentication and quality assessment of S. lateriflora-based dietary supplements have not been reported. In this study, a flow-injection/mass spectrometry fingerprinting method in combination with principal component analysis was used to survey S. lateriflora-based dietary supplements sold in the USA.

Profiling of Glucosinolates and Flavonoids in Rorippa indica (Linn.) Hiern. (Cruciferae) by UHPLC-PDA-ESI/HRMSn

An UHPLC-PDA-ESI/HRMSn profiling method was used to identify the glucosinolates and flavonoids of Rorippa indica (Cruciferae), a wild vegetable and Chinese herb used to treat cough, diarrhea, and rheumatoid arthritis. Thirty-three glucosinolates, more than 40 flavonol glycosides, and 18 other phenolic and common organic compounds were identified. The glucosinolates and polyphenols were separated by UHPLC. High-resolution deprotonated molecules provided high accuracy mass values that were used to determine formulas and provide putative identification of the glucosinolates and flavonoids. The fragments from multistage mass spectrometry were used to elucidate the structures. The concentrations of the main components were based on UV peak areas and molar relative response factors with a single calibration standard. This study found this plant to be a rich source for glucosinolates, containing 24 new glucosinolates, including 14 glucosylated glucosinolates that were previously unidentified.