Centrifugal Partition Chromatography Research Articles

Dereplication of Natural Extracts Diluted in Glycerin: Physical Suppression of Glycerin by Centrifugal Partition Chromatography Combined with Presaturation of Solvent Signals in 13C-Nuclear Magnetic Resonance Spectroscopy.

For scientific, regulatory, and safety reasons, the chemical profile knowledge of natural extracts incorporated in commercial cosmetic formulations is of primary importance. Many extracts are produced or stabilized in glycerin, a practice which hampers their characterization. This article proposes a new methodology for the quick identification of metabolites present in natural extracts when diluted in glycerin. As an extension of a 13C nuclear magnetic resonance (NMR) based dereplication process, two complementary approaches are presented for the chemical profiling of natural extracts diluted in glycerin: A physical suppression by centrifugal partition chromatography (CPC) with the appropriate biphasic solvent system EtOAc/CH3CN/water 3:3:4 (v/v/v) for the crude extract fractionation, and a spectroscopic suppression by presaturation of 13C-NMR signals of glycerin applied to glycerin containing fractions. This innovative workflow was applied to a model mixture containing 23 natural metabolites. Dereplication by 13C-NMR was applied either on the dry model mixture or after dilution at 5% in glycerin, for comparison, resulting in the detection of 20 out of 23 compounds in the two model mixtures. Subsequently, a natural extract of Cedrus atlantica diluted in glycerin was characterized and resulted in the identification of 12 metabolites. The first annotations by 13C-NMR were confirmed by two-dimensional NMR and completed by LC-MS analyses for the annotation of five additional minor compounds. These results demonstrate that the application of physical suppression by CPC and presaturation of 13C-NMR solvent signals highly facilitates the quick chemical profiling of natural extracts diluted in glycerin.

Chemical Profile and Antimicrobial Activity of the Fungus-Growing Termite Strain Macrotermes Bellicosus Used in Traditional Medicine in the Republic of Benin.

The fungus growing termite species Macrotermes bellicosus (M. bellicosus) is used in nutrition and traditional medicine in the Republic of Benin for the treatment of infectious and inflammatory diseases. Previous findings demonstrated evidence of anti-inflammatory and spasmolytic properties of M. bellicosus. The aim of the present study was to evaluate the antimicrobial potential of different extracts of M. bellicosus samples and determine the chemical profile of an ethanolic M. bellicosus extract. Chemical profiling was conducted using centrifugal partition chromatography and 13C-NMR, followed by MALDI-TOF MS. Major identified compounds include hydroquinone (HQ), methylhydroquinone (MHQ), 3,4-dihydroxyphenethyl glycol (DHPG), N-acetyldopamine (NADA) and niacinamide. The fatty acid mixture of the extract was mainly composed of linoleic and oleic acid and highlights the nutritional purpose of M. bellicosus. Using the Kirby–Bauer disc diffusion and broth microdilution assay, an antibacterial activity of M. bellicosus samples was observed against various clinical strains with a highest growth inhibition of S. aureus. In addition, HQ and MHQ as well as fractions containing DHPG, niacinamide and NADA inhibited S. aureus growth. The reported antimicrobial activity of M. bellicosus and identified active substances provide a rationale for the traditional medicinal use of M. bellicosus.

Purification of green fluorescent protein using fast centrifugal partition chromatography

The green fluorescent protein (GFP) is a biomolecule used in many biological applications such as biomarkers and biosensors, which require high purity levels. It is usually obtained from recombinant Escherichia coli strains, which also produces other endogenous proteins, demanding multiple purification steps, and consequently, increasing the overall costs to obtain pure GFP. Simpler and cheaper purification methods like Aqueous Biphasic Systems (ABS) were already successfully applied to purify GFP at lab scale. Therefore, the development of automatized industrially compatible purification platforms, such as countercurrent chromatography using ABS, can potentially improve the GFP production. This work studied the continuous purification of the variant enhanced GFP (EGFP) by applying ABS composed of polyethylene glycol (PEG 8000), sodium polyacrylate (NaPA 8000) and sodium sulfate (Na2SO4) as electrolyte. An initial screening was carried by changing the electrolyte content in the ABS. The increase of this condition has demonstrated an increase on the EGFP partition for the PEG-rich phase. The most efficient ABS and, at the same time, with the most appropriate conditions, namely the system composed of 15 wt% PEG 8000 + 4.5 wt% NaPA 8000 + 2.5 wt% Na2SO4 was chosen and applied on the fast centrifugal partition chromatography (FCPC). After optimization, the best operational conditions were identified, i.e. a flow rate of 2.5 mL.min−1 and rotation speed of 2000 rpm at ascending mode, and the best results obtained, meaning a purification of 89.93% and a recovery yield of 82.3%, confirming the potential of FCPC to the continuous purification of EGFP.

Target-Guided Isolation of O-tigloylcyclovirobuxeine -B from Buxus sempervirens L. by Centrifugal Partition Chromatography.

The increasing drug resistance of malaria parasites challenges the treatment of this life-threatening disease. Consequently, the development of innovative and effective antimalarial drugs is inevitable. O-tigloylcyclovirobuxeine-B, a nor-cycloartane alkaloid from Buxus sempervirens L., has shown promising and selective in vitro activity in previous studies against Plasmodium falciparum (Pf), causative agent of Malaria tropica. For further investigations, it is indispensable to develop an advanced and efficient isolation procedure of this valuable natural product. Accordingly, we used liquid–liquid chromatography including centrifugal partition chromatography (CPC) to obtain the pure alkaloid on a semi-preparative scale. Identification and characterization of the target compound was accomplished by UHPLC/+ESI-QqTOF-MS/MS, 1H NMR and 13C NMR. In conclusion, this work provides a new and efficient method to obtain O-tigloylcyclovirobuxeine-B, a valuable natural product, as a promising antiplasmodial lead structure for the development of innovative and safe medicinal agents.

Bryophyllum pinnatum markers: CPC isolation, simultaneous quantification by a validated UPLC-DAD method and biological evaluations

Bryophyllum pinnatum (Lam.) Oken (Crassulaceae) is widely used as leaf juice or extracts in traditional medicine all over tropical areas, especially in Brazil, to relieve inflammation-associated symptoms. Flavonol glycosides with unusual sugar moiety are among the major metabolites. Nevertheless, there are not enough quality control studies that can contribute to authentication of B. pinnatum and determination of their markers. As it is also used as medicinal plant in several countries, it is necessary to provide data related to safety, efficacy and quality. In this context, this work aims to isolate the major flavonoids from B. pinnatum hydroethanolic extract, to validate a method to quantify the content of chemical markers and to evaluate their xanthine oxidase inhibition and antioxidant activity. The extract was submitted to centrifugal partition chromatography (CPC). The solvents system CyHex-EtOAc-EtOH-H2O, 0.5:9:3:5.5, v/v/v/v was selected by shake-flask method. Four flavonoids (quercetin 3-O-α-L-arabinopyranosyl-(1→2)-O-α-L-rhamnopyranoside (1), kaempferol 3-O-α-L-arabinopyranosyl-(1→2)-O-α-L-rhamnopyranoside (2), quercetin 3-O-α-L-rhamnopyranoside (3) and kaempferol 3-O-α-L-rhamnopyranoside (4)) were isolated in a single and fast CPC run and their structures were confirmed by NMR analysis. An UPLC-DAD quantification method was established for the first time with validation of required parameters, according to RDC 166/2017. The calibration curves were linear with correlation coefficient ranging from 0.9996 to 0.9997 while the values of LOD (0.0077–1.984 ng.mL−1), LOQ (0.0263–6.012 ng.mL−1), recovery (≥ 80.7 %) and inter-day (%RSD ≤ 3.581) and intra-day precision (%RSD ≤ 2.628) were satisfactory. Quantitative analysis of these compounds showed that the proportion of 1, 2 and 3 were 2.43, 0.25 and 0.33 % (24.3 mg.g−1, 0.25 mg.g−1 and 0.33 mg.g−1 of extract), respectively. Moreover, in vitro xanthine oxidase (XO), DPPH and ABTS inhibition were evaluated for the extract and the major flavonoids. Compounds 2 (168 μM) and 3 (124 μM) moderately inhibited XO, while compounds 1 and 3 displayed average radical scavenging activity. In conclusion, our results suggest the flavonoid 1 as a specific marker which may be used for quality control of B. pinnatum hydroethanolic leaves extract.

Development and characterization of a pure stilbene extract from grapevine shoots for use as a preservative in wine

Grapevine shoots, known to be a source of bioactive stilbenes, are considered one of the most important and abundant waste products from the vineyard. The objective of this study was to obtain a pure stilbene extract from grapevine shoots and test its properties, mainly antimicrobial ones, as a preservative in wine. A new extract with a purity of 99% in stilbenes was obtained by centrifugal partition chromatography. The extract was characterized by HPLC-MS, the main compounds being E-ε-viniferin (70%) and E-resveratrol (18%). The stability conditions for the extract solution were low temperature (4 °C) and darkness for a maximum of 21 days. Data regarding to the stability of E-ϵ-viniferin, ω-viniferin and r-viniferin are reported first.The antimicrobial activity of the extract was higher against yeast (Brettanomyces bruxellensis, Zygosaccharomyces bailli, Haseniaspora uvarum, Candida zemplinina) than against bacteria (Lactobacillus hilgardii, Oenococcus oeni, Pediococcus pentasaceus). The best antimicrobial activity was found on Brettanomyces bruxellensis and Zygossaccharomyces bailli. The aromatic characterization of the extract allows us to establish that it does not affect the sensory properties of wine, and thus wine quality is not compromised with the addition of the extract. All of the above allow us to propose ST99 as a promising alternative to SO2 in wines, including rose and white wines.

Pilot continuous centrifugal liquid-liquid extraction of extra virgin olive oil biophenols and gram-scale recovery of pure oleocanthal, oleacein, MFOA, MFLA and hydroxytyrosol

This study provides an efficient pilot-scale liquid-liquid extraction process for the recovery of total phenolic fraction (TPF) from extra virgin olive oil (EVOO) and the further purification of the major TPF constituents (oleocanthal, oleacein, monoaldehydic form of oleuropein aglycone, monoaldehydic form of ligstroside aglycone and hydroxytyrosol) using successively centrifugal partition chromatography and reversed phase high performance liquid chromatography. Special attention was paid for the selection of the appropriate raw material, which should be rich in the targeted high-value compounds. For the extraction of the selected EVOOs, a green technique based on liquid-liquid partitioning using the biphasic system n-Hept/EVOO/EtOH/H2O 3:2:3:2 v/v was carried out, first on pioneering laboratory-scale annular centrifugal extractor (ACE) and then on pilot device. 240 L from three different EVOOs (3x80 L of each EVOO) were extracted yielding 285 g of TPF in approximately 2 h. The second step of this procedure was the purification of the target compounds. A preparative centrifugal partition chromatography (CPC) process was firstly applied for the initial TPF fractionation using a step gradient elution-extrusion method with a series of 4 biphasic systems composed of n-Hept/EtOAc/EtOH/H2O in ratios 4:1:3:2, 3:2:3:2, 2:3:3:2 and 1:4:3:2 (v/v/v/v). Preparative reversed phase high performance liquid chromatography (prep-RP-HPLC) was then carried out to polish the target compounds from the enriched CPC fractions resulting in purity higher than 97%. In parallel, the above purification analysis led to the isolation of four minor TPF constituents of which three are new natural products (EDA lactone, (1R, 8E)-1-ethoxy-ligstroside aglycon and (1S, 8E)-1-ethoxy-ligstroside aglycon) and one ((9E, 11E)-13-oxotrideca-9,11-diencoic acid) is described for the first time as EVOO constituent.

Propranolol resolution using enantioselective biphasic systems

The commercialization of chiral drugs is an increasing concern in the pharmacological field since the differences in the pharmacological activities of enantiomers may result in serious problems in the treatment of diseases using racemates. The resolution of chiral drugs is important for the development of safer and more active pharmaceuticals. This work aims to develop an enantioseparation platform for the resolution of propranolol (R/S-PRP) resorting to esters of tartaric acid and chiral ionic liquids (CILs) as chiral selectors in biphasic systems. More specifically, the efficiency of enantioselective liquid–liquid extraction (ELLE) systems, both aqueous and non-aqueous biphasic systems, are here studied, aiming to do a direct comparison between these two types of systems for the resolution of R/S-PRP. Studies were carried to evaluate the proper phase forming components of ELLE, R/S-PRP:chiral selector ratio, the potential of CILs over esters of tartaric acid, and the most suitable alkyl chain length for the esters of tartaric acid. It was found that the selected organic phase formers of ELLE, 1,2-dichloroethane and ethyl acetate, greatly impact the potential of the enantiorecognition of the system. The most efficient biphasic system identified was composed of 1,2-dichloroethane-water, and dipentyl-L-tartrate and boric acid as chiral selectors, with a enantioselectivity of 2.54. This system was further employed for the resolution of R/S-PRP in centrifugal partition chromatography, to assess its scalability potential, being shown that it was possible to increase the purity of R-PRP from 59% to 75%.

Updated pigment composition of Tisochrysis lutea and purification of fucoxanthin using centrifugal partition chromatography coupled to flash chromatography for the chemosensitization of melanoma cells

Tisochrysis lutea (T. lutea, ex T. Isochrysis galbana or T-Iso) is a marine haptophyte that was first isolated from Tahiti seawater. Because of its high content in lipids, this tropical species is commonly used in aquaculture to feed fishes, crustaceans and molluscs larvae. It is also a rich source of fucoxanthin with a high potential for nutraceutical, cosmetic and pharmaceutical applications. The purpose of the present study was to detail the pigment composition of T. lutea and to develop an efficient process to recover highly purified fucoxanthin. Using ultra performant liquid chromatography coupled to diode arrays and high-resolution mass spectrometry detectors (UPLC-DAD-MS/MS), we demonstrated for the first time the presence of echinenone, 3-hydroxy-echinenone and chlorophyll c2-monogalactosyldiacylglycerol [18:4/14:0] in unstressed cultures of T. lutea. The chemotaxonomic relevance of this updated pigment composition was discussed in relation to the Haptophyta phylum. A two-step purification of fucoxanthin was then optimized using centrifugal partition chromatography coupled to flash chromatography. This process allowed the efficient isolation of fucoxanthin (purity > 99%), that was further assessed as a low-toxicity antineoplastic and chemosensitizing natural product in human chemoresistant melanoma cells. This carotenoid exerted an antiproliferative activity in A2058 melanoma cells and reversed in vitro their chemoresistance to dacarbazine, a DNA-alkylating agent clinically used for the treatment of metastatic melanoma.

Diastereomeric stilbenoid glucoside dimers from the rhizomes of Gnetum africanum

Abstract In a continuing search for neuroprotective stilbenoids, two uncommon diastereomeric stilbenoid glucosides, africanoside A (1) and B (2) as well as fifteen known stilbenes, E-resveratrol, E-gnetifolin E, E-piceid, E-resveratroloside, E-gnetifolin K, E-gnetol, E-isorhapontigenin, E-isorhapontin, E-isorhapontigenin-4′-O-glucopyranoside, E-gnetin C, E-bisisorhapontigenin B, E-gnemonoside A, E-gnemonoside C, E-gnemonoside D, and E-gnetin E, were isolated from rhizomes of Gnetum africanum, using a combination of centrifugal partition chromatography and preparative HPLC. The structure of these two stilbenoids was investigated by NMR, vibrational circular dichroism (VCD), and electronic circular dichroism (ECD) experiments. The absolute configurations of 1, and 2 were established by VCD as (7aS,8aS) and (7aR,8aR), respectively. Compound 1 significantly chelated Fe(II) at 100, 250 and 500 μM. The ability of stilbenoids to chelate ferrous ions which are implicated in physiopathological hallmark of Alzheimer’s disease provides useful data for potential treatment.

Isolation of Three Lycorine Type Alkaloids from Rhodolirium speciosum (Herb.) Ravenna Using pH-Zone-Refinement Centrifugal Partition Chromatography and Their Acetylcholinesterase Inhibitory Activities.

Preparative separation of three lycorine type alkaloids from Rhodolirum speciosum (Amaryllidaceae) was successfully carried out using pH-zone-refinement centrifugal partition chromatography (CPC) using the solvent system methyl-tert-butyl ether/acetonitrile/water (4:1:5, v/v/v) in descending mode. Using this system, Alkaloid 1 (165.7 mg, 88.2%, purity), 2 (60.1 mg, 97.7% purity) and 3 (12.3 mg, 84.4% purity) were obtained in one step. For structure elucidation, the pure alkaloids were subjected to spectroscopy analysis using nuclear magnetic resonance experiments (1H-NMR, 13C-NMR) and gas chromatography coupled with mass spectrometry (GC-MS). Alkaloids 1, 2, and 3 were identified as 1-O-acetyl-5,6-dehydrolycorine, 1-O-acetyl-lycorine, and 1,2-O-diacetyl-5,6-dehydrolycorine, respectively. The acetylcholinesterase inhibitory activity of these alkaloids was IC50 151.1 μg/mL, IC50 203.5 μg/mL, IC50 470.0 μg/mL, and IC50 17.1 μg/mL, respectively.

Bioassay-Guided Separation of Centipeda minima Using Comprehensive Linear Gradient Centrifugal Partition Chromatography

A comprehensive linear gradient solvent system for centrifugal partition chromatography (CPC) was developed for the bioassay-guided isolation of natural compounds. The gradient solvent system consisted of three different ternary biphasic solvents types: n-hexane–acetonitrile–water (10:2:8, v/v), ethyl acetate–acetonitrile–water (10:2:8, v/v), and water-saturated n-butanol–acetonitrile–water (10:2:8, v/v). The lower phase of the n-hexane–acetonitrile–water (10:2:8, v/v) was used as the stationary phase, while its upper phase, as well as ethyl acetate–acetonitrile–water (10:2:8), and water-saturated n-butanol–acetonitrile–water (10:2:8, v/v) were pumped to generate a linear gradient elution, increasing the mobile phase polarity. We used the gradient CPC to identify antioxidant response elements (AREs), inducing compounds from Centipeda minima, using an ARE-luciferase assay in HepG2 cells, which led to the purification of the active molecules 3-methoxyquercetin and brevilin A. The developed CPC solvent systems allow the separation and isolation of compounds with a wide polarity range, allowing active molecule identification in the complex crude extract of natural products.

Antioxidant efficacy of (−)-loliolide isolated from Sargassum horneri against AAPH-induced oxidative damage in Vero cells and zebrafish models in vivo

Seaweed-derived compounds are known to possess various biological activities. The present study evaluated the antioxidant potential of (−)-loliolide, a monoterpenoid isolated from Sargassum horneri in Vero cells and zebrafish models. (−)-Loliolide was purified from the chloroform fraction of an S. horneri methanol extract using high-performance centrifugal partition chromatography (HPCPC). HPCPC was found to be an effective method to isolate (−)-loliolide, yielding a high purity product. Electron spin resonance evaluation demonstrated that (−)-loliolide had significant alkyl radical scavenging activity (IC50: 0.043 ± 0.005 mg mL−1). In addition, our study showed that (−)-loliolide demonstrated dose-dependent protective effects for Vero cell viability against 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced intracellular reactive oxygen species (ROS). Moreover, (−)-loliolide reduced lipid peroxidation in AAPH-induced zebrafish embryos, while ameliorating the survival rate and cell death in a dose-dependent manner. These results reveal the antioxidant potential of (−)-loliolide. Future studies highlighting the potential applications of S. horneri in manufacturing functional food ingredients are required.

Liquid-liquid chromatography in enantioseparations.

Modern liquid-liquid chromatography mainly refers to the following two kinds of chromatographic apparatuses: countercurrent chromatography based on hydrodynamic equilibrium systems and centrifugal partition chromatography based on hydrostatic equilibrium systems. In this paper, the recent advancements in enantioseparations by liquid-liquid chromatography, including the separation mechanism, chiral selector, two-phase solvent system, methods to improve the peak resolution and recent applications, are reviewed. The future outlook for liquid-liquid chromatography in enantioseparations is also proposed.

(-)-Loliolide Isolated from Sargassum horneri Protects against Fine Dust-Induced Oxidative Stress in Human Keratinocytes.

The emergence of fine dust (FD) among air pollutants has taken a toll during the past few decades, and it has provided both controversy and a platform for open conversation amongst world powers for finding sustainable solutions and effective treatments for health issues. The present study emphasizes the protective effects of (–)-loliolide (HTT) isolated from Sargassum horneri against FD-induced oxidative stress in human HaCaT keratinocytes. The purification of (–)-loliolide was carried out by centrifugal partition chromatography. HTT did not show any cytotoxicity, and it further illustrated the potential to increase cell viability by reducing the reactive oxygen species (ROS) production in FD-stimulated keratinocytes. Furthermore, HTT suppressed FD-stimulated DNA damage and the formation of apoptotic bodies, and it reduced the population of cells in the sub-G1 apoptosis phase. FD-induced apoptosis was advancing through the mitochondria-mediated apoptosis pathway. The cytoprotective effects of the HTT against FD-stimulated oxidative damage is mediated through squaring the nuclear factor E2-related factor 2 (Nrf2)-mediated heme oxygenase-1 (HO-1) pathway, dose-dependently increasing HO-1 and NAD(P)H dehydrogenase (quinone) 1 (NQO1) levels in the cytosol while concomitantly improving the nuclear translocation of Nrf2. Future studies could implement the protective functionality of HTT in producing pharmaceuticals that utilize natural products and benefit the diseased.

Selective Chlorophyll Removal Method to "Degreen" Botanical Extracts.

Chlorophylls are present in all extracts from the aerial parts of green plant materials. Chlorophylls may act as in vitro bioassay nuisance compounds, possibly preventing the reproducibility and accurate measurement of readouts due to their UV/vis absorbance, fluorescence properties, and tendency to precipitate in aqueous media. Despite the diversity of methods used traditionally to remove chlorophylls, details about their mode of operation, specificity, and reproducibility are scarce. Herein, we report a selective and efficient 45 min liquid-liquid/countercurrent chlorophyll cleanup method using Centrifugal Partition Chromatography (CPC) with a solvent system composed of hexanes-EtOAc-MeOH-water (5:5:5:5, v/v) in elution-extrusion mode. The broader utility of the method was assessed with four different extracts prepared from three well-characterized plant materials: Epimedium sagittatum (leaves), Senna alexandrina (leaves), and Trifolium pratense (aerial parts). The reproducibility of the method, the selectivity of the chlorophyll removal, as well as the preservation of the phytochemical integrity of the resulting chlorophyll-free ("degreened") extracts were evaluated using HPTLC, UHPLC-UV, 1H NMR spectroscopy, and LC-MS as orthogonal phytochemical methods. The cleanup process adequately preserves the metabolomic diversity as well as the integrity of the original extracts. This method was found to be sufficiently rapid for the "degreening" of botanical extracts in higher-throughput sample preparation for further biological screening.

Anthelmintic A-Type Procyanidins and Further Characterization of the Phenolic Composition of a Root Extract from Paullinia pinnata.

Extracts from the roots of Paullinia pinnata L. are used in West Africa as traditional remedies for a variety of diseases including infestations with soil-transmitted helminths. Based on the results of an ethnopharmacological survey in Ghana, an aqueous acetone (70%) extract was investigated for its anthelmintic and phytochemical properties. Partitioning of the crude extract followed by several fractionation steps of the ethyl acetate phase using Sephadex® LH-20, fast centrifugal partition chromatography, RP-18-MPLC and HPLC led to isolation of six oligomeric A-type procyanidins (1 to 6). To determine the anthelmintic activity, the crude extract, fractions and isolated compounds were tested in vitro against the model organism Caenorhabditis elegans. A significantly better activity was observed for the trimeric A-type procyanidin (1) compared to a B-type trimer. However, this effect could not be generalized for the tetrameric procyanidins, for which the type of the interflavan-linkage (4→6 vs. 4→8) had the greatest impact on the bioactivity. Besides the procyanidins, three novel compounds, isofraxidin-7-O-α-l-rhamnopyranosyl-(1″→6′)-β-d-glucopyranoside (17), 4-methoxycatechol-2-O-(5′′-O-vanilloyl-β-apiofuranosyl)-(1′′→2′)-β-glucopyranoside (18) and a 6-(3-methoxy-4-hydroxyphenyl)-hexane-2,4-diol-2-O-hexoside (19) were isolated together with further ten known compounds (7 to 16), mainly coumarins and coumarinolignans. Except for 3-β-d-glucopyranosyloxy-4-methyl-2(5H)-furanone (15), none of the isolated compounds has previously been described for P. pinnata. The anthelmintic activity was attributed to the presence of procyanidins, but not to any of the other compound classes. In summary, the findings rationalize the traditional use of P. pinnata root extracts as anthelmintic remedies.

Phytochemical analysis of olive flowers' hydroalcoholic extract and in vitro evaluation of tyrosinase, elastase and collagenase inhibition activity

Olea europaea L. is historically one of the most important trees of the Mediterranean countries. Increasing scientific interest regarding its fruits, leaves and olive oil has led to the elucidation of several phytochemical and biological characteristics. However, the phytochemical and biological studies regarding olive flowers remain limited. The aim of the present study was the phytochemical characterization of olive flowers' hydroalcoholic extract from Greek variety Lianolia, the effective isolation of the major secondary metabolites and evaluation of their inhibition activity against tyrosinase, elastase and collagenase. UPLC-HRMS/MS analysis was used to investigate the chemical composition of hydroalcoholic extract resulting in the identification of sixty-three secondary metabolites witch mainly belong to phenilethanoids, triterpenoids, flavonoids and secoiridoids. The orthogonial combination of Centrifugal Partition Chromatography and preparative HPLC in the same purification process led to the isolation of nine major compounds of the extract including two triterpenic acids, two flavonoid glycosides and five secoiridoid derivatives. From them, oleofloside A and oleofloside B are new natural products. Although, the hydroalcoholic extract and isolated secoiridoids exhibited weak or no inhibition activity towards tyrosinase and elastase, they exhibit remarkable anti-collagenase activity with 2΄-ethoxyoleuropein being the most active compound.

Input of an Off-Line, Comprehensive, Three-Dimensional Method (CPC×SFC/HRMS) to Quantify Polycyclic Aromatic Hydrocarbons in Vacuum Gas Oils

Heavy polycyclic aromatic hydrocarbons (HPAHs) are known to cause undesirable effects in petroleum hydrocracking processes by deactivating the catalysts and accumulating in the downstream of reactors. Polycyclic aromatic hydrocarbons with less than seven rings (PAHs) naturally contained in vacuum gas oils (VGOs) act as precursors in the HPAHs formation. However, getting a detailed quantitative characterization of such polycyclic hydrocarbons has never been done until now, because of the high chemical complexity of VGOs. Thus, an off-line, comprehensive, three-dimensional methodology was required to achieve a quantitative analysis: centrifugal partition chromatography (CPC) as the first dimension of separation, supercritical fluid chromatography (SFC) as the second dimension hyphenated to Fourier transform ion cyclotron resonance mass spectrometry as the third dimension. In this study, we demonstrated that the developed CPC method fractionated samples according to the hydrocarbons' alkylation degree, whereas our SFC method provided an elution order according to their double bond equivalent. Finally, high-resolution mass spectrometry (HRMS) brought crucial information on the identity of analytes and proved to be essential in the event of unresolved peaks from CPC and SFC chromatograms. To assess the ability of the three-dimensional method for quantification purposes, matrix effects were evaluated by spiking VGO samples with deuterated pyrene. A strong ion suppression phenomenon was highlighted when using only SFC/HRMS, whereas no significant matrix effect was observed with the CPC×SFC/HRMS approach. These experiments revealed the great potential of this innovative methodology to quantify both PAH and HPAH in VGOs for the first time.

Abundant Extractable Metabolites from Temperate Tree Barks: The Specific Antimicrobial Activity of Prunus Avium Extracts.

Tree barks are mainly considered as wood wastes from forestry activities, but represent valuable resources as they may contain antimicrobial compounds. Here, we aimed to evaluate the possible antimicrobial activities of bark extracts and to characterize the chemical composition of the most active extract. Ten methanol bark extracts were tested in vitro against 17 bacterial strains and 5 yeast strains, through minimum inhibitory concentration (MIC) and minimum bactericidal (or fungicidal) concentration (MBC/MFC) assays. The extract from Prunus avium (E2-4) displayed the largest bactericidal activity against Gram-positive bacteria, with a lethal effect on 6 out of 8 strains. Antibiofilm assays of E2-4 were performed by crystal violet staining and enumeration of adhered bacteria. Assays demonstrated a biofilm inhibitory effect of E2-4 against Staphylococcus aureus CIP 53.154 at concentrations equal to or higher than 250 µg/mL. Chemical profiling of E2-4 by 13C nuclear magnetic resonance (NMR) revealed the presence of dihydrowogonin as a major constituent of the extract. E2-4 was fractionated by centrifugal partition chromatography and the three fractions containing dihydrowogonin were tested for their antibacterial and antibiofilm activities, revealing similar activities to those of E2-4. Dihydrowogonin was positively assessed as an interesting antimicrobial compound, which could be valued from wastes of Prunus avium barks.