RP-HPLC Separation and 1H NMR Identification of a Yellow Fluorescent Compound-Riboflavin (Vitamin B2)-Produced by the Yeast Hyphopichia wangnamkhiaoensis

The yeast Hyphopichia wangnamkhiaoensis excretes a brilliant yellow fluorescent compound into its growth culture. In this study, we isolated and identified this compound using reverse-phase high-performance liquid chromatography-diode array detector (RP-HPLC-DAD) as well as 1H NMR and UV-Vis spectroscopy. Two of the three RP-HPLC-DAD methods used successfully separated the fluorescent compound and involved (1) a double separation step with isocratic flow elution, first on a C18 column and later on a cyano column, and (2) a separation with a linear gradient elution on a phenyl column. The wavelengths of maximum absorption of the fluorescent compound-containing HPLC fractions (~224, 268, 372, and 446 nm) are in good agreement with those exhibited by flavins. The 1H NMR spectra revealed methyl (δ 2.30 and 2.40) and aromatic proton (δ 7.79 and 7.77) signals of riboflavin. The 1H NMR spectra of the samples spiked with riboflavin confirmed that the brilliant yellow fluorescent compound is riboflavin. The maximum excitation and emission wavelengths of the fluorescent compound were 448 and 528 nm, respectively, which are identical to those of riboflavin.

Phytochemicals Recovery from Grape Pomace: Extraction Improvement and Chemometric Study

In the last 20 years, an increased interest has been shown in the application of different types and combinations of enzymes to obtain phenolic extracts from grape pomace in order to maximize its valorization. Within this framework, the present study aims at improving the recovery of phenolic compounds from Merlot and Garganega pomace and at contributing to the scientific background of enzyme-assisted extraction. Five commercial cellulolytic enzymes were tested in different conditions. Phenolic compound extraction yields were analyzed via a Design of Experiments (DoE) methodology and a second extraction step with acetone was sequentially added. According to DoE, 2% w/w enzyme/substrate ratio was more effective than 1%, allowing a higher total phenol recovery, while the effect of incubation time (2 or 4 h) variation was more enzyme-dependent. Extracts were characterized via spectrophotometric and HPLC-DAD analyses. The results proved that enzymatic and acetone Merlot and Garganega pomace extracts were complex mixtures of compounds. The use of different cellulolytic enzymes led to different extract compositions, as demonstrated using PCA models. The enzyme effects were observed both in water enzymatic and in the subsequent acetone extracts, probably due to their specific grape cell wall degradation and leading to the recovery of different molecule arrays.

A dispersive liquid-liquid microextraction followed by reverse-phase high-performance liquid chromatography for QuEChERS determination of chlorogenic acid

INTRODUCTION

The presence of chlorogenic acid (CGA) not only imparts a characteristic flavour to foods but also makes them useful against chronic diseases and metabolic syndromes, especially diabetes mellitus and asthma.

OBJECTIVES

The present study was designed to develop a quick, easy, cheap, effective, rugged, and safe (QuEChERS) and pragmatic method to analyse CGA in plant-based products by applying dispersive liquid-liquid microextraction (DLLME) followed by reverse-phase high-performance liquid chromatography under a diode array detector (RP-HPLC-DAD).

METHODOLOGY

The DLLME was carried out using Triton X-100 as a dispersant and ethanol as an extraction solvent, while method development and validation activities were performed on a Shimadzu 10-AT HPLC-DAD system equipped with C-18 columns as stationary phases.

RESULTS

The well-resolved peak for the standard CGA was observed at 2.92 min for the mobile phase comprising 0.1% aqueous formic acid-ethanol (22:78 v/v) of pH 3.0 programmed under an isocratic flow rate of 1.0 mL/min. The developed method was found to be linear (R²  = 0.9976) over 1-500 μg/mL of CGA concentration at 328 nm. Moreover, the assay was found to be repeatable with RSD ≤ 5.0, and the limit of detection (LOD) and limit of quantification (LOQ) were 0.0281 and 0.0853 μg/mL of CGA, respectively. The DLLME offered an overall recovery rate between 97.60% and 99.54% at an acceptable level of reproducibility [relative standard deviation (RSD) ≤ 5.0].

CONCLUSION

The developed assay was found to be a QuEChERS and pragmatic choice for the high-throughput analysis of CGA in plant-based products/foods. Finally, the analysis revealed the presence of an ample level of CGA in guava fruit in addition to coffee beans and black tea.

Comparison of Differences in Chemical Composition and Related Antioxidant Activity of Snow Lotus from Different Origins

The snow lotus is an endangered traditional Chinese medicinal herb. Saussurea involucrata, Saussurea laniceps, and Saussurea medusa, the three main snow lotus species (five herbs and two S. involucrata cell cultures), were selected for this study. Snow lotus (XLs) was extracted using 75 % (v/v) ethanol. Two reversed phase-high performance liquid chromatography-diode array detector methods were developed and validated for the determination of 10 representative components in XLs. The antioxidant efficacy of XLs and their components was investigated using DPPH, ABTS free radical scavenging, and ROS inhibition experiments. The results showed that the IC₅₀ for DPPH scavenging ranged from 0.06-0.29 mg/mL for XLs and from 0.13-0.63 mg/mL for ABTS, and could downregulate ROS to varying degrees. The results of the antioxidant activity showed that rutin, quercetin, and isochlorogenic acid A contributed to the antioxidant capacity of XLs. The high content and activity of the cell cultures indicate that they can serve as an effective alternative to snow lotus, thus providing a theoretical basis for the selection of herbs and cell cultures to fulfil various needs.

Application of HPLC-QQQ-MS/MS and New RP-HPLC-DAD System Utilizing the Chaotropic Effect for Determination of Nicotine and Its Major Metabolites Cotinine, and trans-3'-Hydroxycotinine in Human Plasma Samples

The routine techniques currently applied for the determination of nicotine and its major metabolites, cotinine, and trans-3′-hydroxycotinine, in biological fluids, include spectrophotometric, immunoassays, and chromatographic techniques. The aim of this study was to develop, and compare two new chromatographic methods high-performance liquid chromatography coupled to triple quadrupole mass spectrometry (HPLC-QQQ-MS/MS), and RP-HPLC enriched with chaotropic additives, which would allow reliable confirmation of tobacco smoke exposure in toxicological and epidemiological studies. The concentrations of analytes were determined in human plasma as the sample matrix. The methods were compared in terms of the linearity, accuracy, repeatability, detection and quantification limits (LOD and LOQ), and recovery. The obtained validation parameters met the ICH requirements for both proposed procedures. However, the limits of detection (LOD) were much better for HPLC-QQQ-MS/MS (0.07 ng mL⁻¹ for trans-3′-hydroxcotinine; 0.02 ng mL⁻¹ for cotinine; 0.04 ng mL⁻¹ for nicotine) in comparison to the RP-HPLC-DAD enriched with chaotropic additives (1.47 ng mL⁻¹ for trans-3′-hydroxcotinine; 1.59 ng mL⁻¹ for cotinine; 1.50 ng mL⁻¹ for nicotine). The extraction efficiency (%) was concentration-dependent and ranged between 96.66% and 99.39% for RP-HPLC-DAD and 76.8% to 96.4% for HPLC-QQQ-MS/MS. The usefulness of the elaborated analytical methods was checked on the example of the analysis of a blood sample taken from a tobacco smoker. The nicotine, cotinine, and trans-3′-hydroxycotinine contents in the smoker’s plasma quantified by the RP-HPLC-DAD method differed from the values measured by the HPLC-QQQ-MS/MS. However, the relative errors of measurements were smaller than 10% (6.80%, 6.72%, 2.04% respectively).

Reversed-Phase HPLC Characterization and Quantification and Antioxidant Capacity of the Phenolic Acids and Flavonoids Extracted From Eight Varieties of Sorghum Grown in Austria

Sorghum is raising great interest as a grain for the future, for its agricultural advantages in times of climate change, and for the positive impact of its bioactive compounds on human health. These compounds comprise phenolic acids, in a free, conjugated, and bound form, and flavonoids. The most commonly used extraction methods require high volumes of chemicals and are non-practical when handling many samples at a time. The main aim of this study was to develop a microscale extraction procedure for both phenolic acids and flavonoids to improve yield and diversity, labor time, and chemicals usage. The improved protocols allowed to perform the extraction in 2-ml safe-lock tubes using around 60 times less chemical volume for phenolic acids and 6 times less for flavonoids. In addition, compared to the macroscale method, the microscale approach was effective in extracting a comparable amount of phenolic acids (between 0.99 and 1.57 mg ferulic acid/g) and even a higher quantity of flavonoids (between 1.10 and 2.24 mg ferulic acid/g). With the established methods, phenolic compounds were extracted from eight varieties of sorghum grown in Austria, previously shown to be promising for food processing. In all sorghum varieties, protocatechuic, vanillic, caffeic, syringic, P-coumaric, and ferulic acids were detected in free, conjugated and bound form, with the last being the most abundant. Arsky and Icebergg varieties presented the lowest (922.65 μg/g) and the highest (1,269.28 μg/g) levels of total phenolic acids, respectively, recorded using high-performance liquid chromatography (HPLC). Flavonoids, comprising luteolinidin, apigenidin, naringenin, apigenin, 5-methoxy-luteolinidin (5-MetO-Lut), and 7-methoxy-apigeninidin (7-MetO-Api), were detected in amounts between 27.03 (Kalatur variety) and 87.52 μg/g (Huggo variety). The red varieties, Huggo, Armorik, and Arsky, had the highest antioxidant activity measured as 2,2-Diphenyl-1-picrylhydrazyl (DPPH) [around 5.00 μg Trolox equivalent (TE)/g] and Azino-bis(3-ehtylbenzthiazoline-6-sulfonic acid) (ABTS) (around 3.00 μg TE/g) scavenging capacity for both phenolic acids and flavonoids. Ferric reducing antioxidant power (FRAP) was the highest for the phenolic acids extracted from a white Ggolden variety.

RP-HPLC-DAD determination of the differences in the polyphenol content of Fucus vesiculosus extracts with similar antioxidant activity

Significant quantities of bioactive compounds have been found in the chemical composition of seaweeds. This source of natural antioxidants such as polyphenols appears to attenuate lipid peroxidation caused by oxidative stress, preventing the harmful effects of a number of injuries including ischemia-reperfusion (I/R). Conventional extraction (CE) has been used for years as a traditional method for obtaining bioactive components from seaweeds. However, recent studies highlight ultrasonic-assisted extraction (UAE) as an alternative and more eco-friendly technique. Therefore, the two methods were optimised and compared to obtain a Fucus vesiculosus extract (FVE) with high antioxidant activity and polyphenol content. The highest antioxidant activity was obtained after 1 h at 25 °C for conventional extraction, and after 5 min at 35 °C for ultrasonic-assisted extraction. Higher concentrations of polyphenols were obtained with the optimal conditions in conventional extraction (13.61 mg PGE/g seaweed), but no significant differences were observed between the antioxidant activity obtained with UAE (89.33%) and CE (89.74%). The characterization of the polyphenols present in both optimised extracts was carried out and compared with reverse-phase high-performance liquid chromatography coupled to a diode array detector (HPLC-DAD). The following compounds were identified: phloroglucinol, gallic acid, catechin, vanillic acid, epicatechin, protocatechuic acid, rutin, gentisic acid, chlorogenic acid, caffeic acid, coumaric acid and ferulic acid. RP-HPLC-DAD results also showed higher concentrations of polyphenols in optimised extracts with CE. Consequently, CE was found to be more effective than UAE in providing extracts with higher concentrations of polyphenols, but UAE constitutes an efficient and more eco-friendly methodology for obtaining a FVE with the highest antioxidant activity.

Varietal influence on phenolic constituents and nutritive characteristics of pomace obtained from apples grown in western Himalayas

Apple fruit processing is not variety specific in India, which affect the overall quality of the final processed product. The present study was aimed at elucidation of the nutritive value, phenolic content, antioxidant activity and bioactive phenolic constituents of five widely used apple varieties (Royal Delicious, Red Delicious, Golden Delicious, Red Chief and Red Gold) of western Himalayas. The pomace obtained from different varieties was evaluated to assess the fruit quality. Royal Delicious pomace had significantly high (p < 0.05) total dietary fibre content (42.63 ± 1.26%) together with soluble (8.25 ± 0.95%) and insoluble fibre (32.90 ± 0.89%), as compared to other apple varieties. The pomace samples were extracted with 70% aqueous methanol to obtain polyphenol enriched extracts. The results of Folin-Ciocalteau assay showed that hydroalcoholic extract of Royal Delicious pomace exhibit higher phenolic content as compared to other varieties and ranged between 2.19 ± 0.09 and 4.59 ± 0.47 mg GAE/g. Royal Delicious pomace also possess higher antioxidant capacity i.e. 3.35 ± 0.10 mg/g, 2.71 ± 0.10 mg/g and 4.67 ± 0.03 mg/g as measured by DPPH, ABTS free radical scavenging assay and FRAP reducing assay, respectively. The higher phenolic content in Royal Delicious pomace was also confirmed by RP-HPLC-DAD analysis. Results of HPLC analysis revealed the presence of phloridzin (487.07 ± 0.04 µg/g), quercetin (241.18 ± 0.03 µg/g), quercitrin (178.34 ± 0.02 µg/g) and quercetin-3-glucoside (195.21 ± 0.05 µg/g) as major constituents. Present results indicate that Royal Delicious variety is rich in dietary fibre and phenolic compounds that might be used by the food sector as a source of bioactive health promoting constituents/dietary supplements.

HPLC Analysis of Carotenoids in Neurosporaxanthin-Producing Fungi

The ascomycetous fungi Fusarium fujikuroi and Neurospora crassa are widely used as research models in the study of secondary metabolism and photobiology, respectively. Both fungi exhibit a similar carotenoid pathway, for which all the genes and enzymes have been identified. Under standard laboratory conditions, either F. fujikuroi or N. crassa accumulate a mixture of neurosporaxanthin, a carboxylic apocarotenoid acid, and several of its carotene precursors. We formerly described methods for the identification and quantification of neurosporaxanthin. However, the differences in polarity between this acidic xanthophyll and neutral carotenes make their global analysis cumbersome. Here we propose a simple HPLC methodology for the efficient separation of neurosporaxanthin and earlier pathway intermediates in a single HPLC run. This method should be useful to check the abundance of neurosporaxanthin under different experimental conditions and to evaluate the relative proportions of their different carotene precursors. To assess the validity of the method, we have compared the carotenoid profiles in samples of mycelia of F. fujikuroi and conidia of N. crassa, in both cases obtained from surface cultures of a wild strain of each species.

Extraction efficiency, phytochemical profiles and antioxidative properties of different parts of Saptarangi (Salacia chinensis L.) - An important underutilized plant

The study aimed to evaluate extraction efficiency, detection and quantification of phytochemicals, minerals and antioxidative capacity of different parts of Salacia chinensis L. Continuous shaking extraction, steam bath assisted extraction, ultrasonic extraction and microwave assisted extraction with varied time intervals were employed for extraction of phenolics, flavonoids, and antioxidants. Preliminary screening revealed the presence of wide array of metabolites along with carbohydrates and starch. Steam bath assisted extraction for 10 min exposure was found most suitable for extraction phenolics (46.02 ± 2.30 mg of gallic acid equivalent per gram of dry weight and 48.57 ± 2.42 mg of tannic acid equivalent per gram of dry weight) and flavonoids (35.26 ± 1.61 mg of quercetin equivalent per gram of dry weight and 51.60 ± 2.58 mg of ellagic acid equivalent per gram of dry weight). In support, reverse phase-high performance liquid chromatography- diode array detector confirmed the presence of seven pharmaceutically important phenolic acids. Antioxidant capacity was measured by 1, 1- diphenyl-1-picryl hydrazyl (DPPH), ferric reducing antioxidant power (FRAP), 2, 2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) scavenging (ABTS) and N, N-dimethyl-p-phenylenediamine (DMPD) assays and represented as trolox equivalent antioxidant capacity (TEAC) and ascorbic acid equivalent antioxidant capacity (AEAC). Antioxidant capacity ranged from 121.02 ± 6.05 to 1567.28 ± 78.36 µM trolox equivalent antioxidant capacity and 56.62 ± 2.83 to 972.48 ± 48.62 µM ascorbic acid equivalent antioxidant capacity. Roots showed higher yields of illustrated biochemical parameters, however fresh fruit pulp was found a chief source of minerals. Gas chromatography-mass spectroscopic analysis revealed the presence of a vast array of phytoconstituents associated with different plant parts. The present study revealed the amounts of minerals and diverse phytoconstituents in various parts of S. chinensis and confirmed its medicinal and nutritional implications.

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Comparative illustration of phytochemicals, minerals and antioxidants from various parts of S. chinensis.

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Phytochemical profiling confirmed the presence of different secondary metabolites along with proteins and carbohydrates.

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Chromatographic determination revealed the presence of 7 phenolic acids (RP-HPLC-DAD) and 32 (GC-MS) other compounds.

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Steam bath assisted extraction (10 min) was found effective for the extraction of phenolics, flavonoids and antioxidants.

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Roots are the chief source of secondary metabolites and validated its role in traditional medicine.

HPLC-DAD Method for the Pharmacokinetic Interaction Study of Atorvastatin with Pioglitazone and Cholestyramine in Wistar Rats

Carotid intima-media thickness is used as a surrogate marker for cardiovascular complications in diabetes mellitus. The combination of atorvastatin and pioglitazone was found to be effective in reducing the thickness of the carotid intima-media layer. The method of RP-HPLC coupled with a diode array detector (DAD) was developed for the pharmacokinetic interaction study of atorvastatin with pioglitazone and cholestyramine, respectively, in Wistar rats. Atorvastatin (ATR) and pioglitazone (PIO) were resolved on a C₁₈ column with a mobile phase composed of 48% methanol, 19% acetonitrile, and 33% 10 mM ammonium formate (v/v/v; pH 3.5±0.3, by formic acid) and a 260 nm detection wavelength on the diode array detector. The method was validated according to international standards with good reproducibility and linear response; mean (r) 0.9987 and 0.9972 to ATR and PIO, respectively. The coefficients of variation of intra- and interassay precision ranged between 4.95–8.12 and 7.29–9.67, respectively. Pharmacokinetic parameters were determined in rats following an oral administration of atorvastatin in the presence and absence of pioglitazone and also with cholestyramine. Compared with the control given atorvastatin alone, the C_max and AUC of atorvastatin were merely unchanged in rats with the co-administration of pioglitazone, while they decreased by nearly 21 and 15%, respectively, with the concurrent use of cholestyramine. There were no significant changes in T_max and the plasma half-life (T_1/2) of atorvastatin in both cases. The performed experiment demonstrated that the presented method was suitable for the estimation and pharmacokinetic interaction study of atorvastatin with pioglitazone and cholestyramine in Wistar rat plasma.