Acid Alkyl Esters Research Articles

Comprehensive evaluation of ibuprofenate amino acid isopropyl esters: insights into antioxidant activity, cytocompatibility, and cyclooxygenase inhibitory potential.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used for pain relief and inflammation management, but there are challenges related to poor solubility and bioavailability. We explored modifications of ibuprofen (IBU) by forming ionic pairs using amino acid alkyl esters to enhance solubility without compromising the ability to inhibit cyclooxygenase (COX)-1 and COX-2). We comprehensively evaluated the pharmacological properties of the IBU derivatives, focusing on antioxidant activity (based on the ability to scavenge DPPH and ABTS), biocompatibility (using human dermal fibroblasts), and COX inhibitory potential. The antioxidant activity assays significantly enhanced DPPH scavenging activity for several IBU derivatives, particularly [L-SerOiPr][IBU], suggesting potential therapeutic benefits. There was enhanced cell viability with select derivatives, indicating possible stimulatory effects on cellular proliferation. Finally, predominant COX-1 inhibition across derivatives was consistent with IBU's profile. This study provides insights into the pharmacological properties of IBU amino acid derivatives, highlighting their potential as therapeutic agents. Further exploration into structure-activity relationships and in vivo efficacy warranted to advance these derivatives toward clinical applications, offering prospects for novel NSAIDs with enhanced efficacy and reduced side effects.

Bioaccessible Phenolic Alkyl Esters of Wine Lees Decrease COX-2-Catalyzed Lipid Mediators of Oxidative Stress and Inflammation in a Time-Dependent Manner.

Lipophenols, phenolic compounds esterified with fatty alcohols or fatty acids, provide greater health benefits upon dietary ingestion of plant-based foods than unesterified (poly)phenols. Based on this premise, the present study aimed to demonstrate the role of gastrointestinal enzymes (pepsin, pancreatin, and pancreatic lipase) in releasing alkyl gallates and trans-caffeates from wine lees, providing bioactive compounds with enhanced capacities against oxidative stress (OS) and para-inflammation. The UHPLC-ESI-QqQ-MS/MS-based analysis revealed ethyl gallate and ethyl trans-caffeate as the most prominent compounds (1.675 and 0.872 μg/g dw, respectively), while the bioaccessibility of the derivatives of gallic and caffeic acids was dependent on the alkyl chain properties. The de novo formation of alkyl gallates during gastric and intestinal digestion resulted from intestinal enzyme activity. Moreover, the in vitro capacity of bioaccessible alkyl esters of gallic and trans-caffeic acids to reduce cyclooxygenase-2 concentration and modulate oxilipins related to OS (8-iso-PGF2α) and inflammation (PGF2α and PGE2) was demonstrated in a time-dependent manner. In conclusion, the presence of alkyl esters of gallic and trans-caffeic acids in wine lees and their subsequent formation during digestion of this byproduct emphasize their value as a source of antioxidant and anti-inflammatory compounds, encouraging the consideration of wine lees as a valuable ingredient for health-promoting coproducts.

Synthesis of ω-Hydroxy Fatty Acid Alkyl Esters by Macrocyclic Lactones Alcoholysis Catalyzed by Homoleptic and Heteroleptic Zinc Aryloxides.

A series of zinc aryloxides, [Zn4(sal-Me)8]⋅2.5(C7H8) (1), [Zn4(sal-Me)8]⋅CH2Cl2 (2), [Zn4(μ3-OR)2(sal-R)6] (3) (for R=Me (0.51), Et (0.49)), [Zn4(μ3-OMe)4(sal-Me)4(HOMe)4] (4), [Zn(sal-Me)2(py)2]⋅THF (5), {[Zn(sal-Me)2(tmbpy)] ⋅ 2(C6H5CH3)}n (6), [Zn2(sal-Me)2(THF)2Cl2] ⋅ 0.5(C6H5CH3) (7), and [Zn4(μ3-OMe)2(sal-Me)4Cl2] (8) (Hsal-Me=methyl salicylate, py=pyridine, tmbpy=4,4'-trimethylenedipyridine) were obtained that have different nuclearities and central core topologies and contain ligands of different basicity and coordination abilities.

Production of Sustainable Liquid Fuels

As the world aims to address the UN Sustainable Development Goals (SDGs), it is becoming more urgent for heavy transportation sectors, such as shipping and aviation, to decarbonise in an economically feasible way. This review paper investigates the potential fuels of the future and their capability to mitigate the carbon footprint when other technologies fail to do so. This review looks at the technologies available today, including, primarily, transesterification, hydrocracking, and selective deoxygenation. It also investigates the potential of fish waste from the salmon industry as a fuel blend stock. From this, various kinetic models are investigated to find a suitable base for simulating the production and economics of biodiesel (i.e., fatty acid alkyl esters) and renewable diesel production from fish waste. Whilst most waste-oil-derived biofuels are traditionally produced using transesterification, hydrotreating looks to be a promising method to produce drop-in biofuels, which can be blended with conventional petroleum fuels without any volume percentage limitation. Using hydrotreatment, it is possible to produce renewable diesel in a few steps, and the final liquid product mixture includes paraffins, i.e., linear, branched, and cyclo-alkanes, with fuel properties in compliance with international fuel standards. There is a wide range of theoretical models based on the hydrodeoxygenation of fatty acids as well as a clear economic analysis that a model could be based on.

Biodiesel synthesis via heterogeneous catalysis: investigation of the catalytic performance of CLV98/900 on quality and yield at different production scales

This article investigated the obtaining of fatty acid alkyl esters (FAAE) from waste cooking oil (WCO) via heterogeneous catalysis, applying a catalyst based on mixed oxides (Na-FeAlO) from the red mud (RM) sintering process with sodium carbonate, which was called CLV98/900. The synthesized catalyst was characterized by thermogravimetric analysis, differential thermogravimetry and differential calorimetric analysis (TG/DTG and DSC), Raman spectroscopy, and specific surface area (BET). The influence of the operational parameters oil/alcohol molar ratio (1:15 and 1:45), reaction time (60, 120 and 180 min) and scale-up on the yield and conversion of the reaction into biodiesel produced were investigated. The catalyst characterization indicated an efficient microstructural transformation of the red mud, thermal stability at the study temperature of 70 ºC, and a mesoporous characteristic. The best yield and reaction conversion results were obtained with the parameters: oil/ethanol ratio of 1:15, 70 °C, 1% catalyst and 60 min, achieving yield and conversion of approximately 75%. The formation of biodiesel was confirmed by GC-MS analysis, reaching a maximum of 100% conversion to the lower phase obtained after the purification process. Therefore, CLV98/900 becomes a promising option when used as a catalyst in biodiesel production through the transesterification reaction of WCO.

Utilization of Macadamia nut oil as a feedstock for a Sustainable Biodiesel Production

Although fossil fuel continues to play a dominant role in global energy system unfortunately their life span is threatened as the fossil reserves are running out. Except for the fact that they are readily available, tried and tested, unfortunately they bring about a negative environmental and climate impact. When the fossil fuels are burned, they produce both carbon dioxide and carbon monoxide which is the largest driver of global climate change and air pollution. This has caused a need to explore and transition to a cleaner and renewable energy resource like biofuel. Biofuel is a combination of fatty acid alkyl esters achieved by the esterification and transterification of triglycerides that can either be animal fats and vegetable oil with methanol and ethanol. Biodiesel provides several positive benefits by helping in decreasing the country’s dependence on the importation of crude oils, it also reduces the greenhouse gas emissions and advances the lubricating property. Biodiesel is produced and deployed globally with China being the country with the highest biofuel capacity in the world, with nearly 29.8 gigawatts as of 2021. It is followed by Brazil which is ranked second, with a biofuel capacity of 16.3 gigawatts. The selection of a feedstock in biofuel production has a noticeable impact as it determines if a biofuel will be formed or not from the transesterification process performed. The fatty acid / triglyceride content especially the Mono-Unsaturated Fatty Acids (MUFA’s) are of interest. The higher the MUFA’s, the higher possibility of a successful transterification hence biofuel being the by-products/formation with less catalyst and alcohol used. Feedstocks with over 40% fatty acids, especially the MUFA’s are favorable for biodiesel formation. Almost 80% of Macadamia’s fatty acids (MFAs) are palmitoleic acids (C16:1; ~20%) and Monounsaturated, mostly oleic (C18:1; ~60%). This study reviews the preparation of biofuel utilizing Macadamia nut oil (MNO) as a feedstock for sustainable biodiesel Production.

Liquid to solid phase transition detection by using a vibrating tube densimeter along with densities up to 137 MPa of beef tallow fatty acid alkyl esters

Phase behavior and thermophysical properties of biodiesel at high pressure and high temperature are limited in the literature. These are useful to develop models and to understand their behavior having in mind the use of biodiesel in engines. Liquid to solid phase transitions, by using a vibrating tube densimeter, along with densities of three beef tallow fatty acid alkyl esters were studied in this work. Measurements of the oscillating period for each biofuel were carried out in a modular array constituted by two vibrating tube densimeters coupled in series and connected to a single loading cell. The oscillating period was converted to density by the forced path mechanical calibration (FPMC) method. Experimental liquid density sets for three beef tallow biodiesel samples based on fatty acid alkyl esters (FAAEs) are reported for the first time for pressures up to 137 MPa. These biofuels, named fatty acid methyl esters (FAMEs), fatty acid ethyl esters (FAEEs) and fatty acid butyl esters (FABEs), were measured in the temperature range of 286–393 K. The detection procedure for the beginning of the high-pressure solidification was focused on the beef tallow FABEs sample based upon its lower cloud point (CPFABEs = 281.15 K) in comparison with the reported property for the other esters (CPFAEEs = 289.15 K, CPFAMEs = 291 K) with the same feedstock; therefore, the conditions for the metastable liquid to solid phase transition associated to the effect of high pressure was detailed for waste beef tallow butyl ester biodiesel by performing step-by-step compressions in the interval of 286.20–298.13 K and with the help of the vibrating tube densimeters. FABEs had the lower density in contrast with FAEEs and FAMEs, this one being the denser biofuel. Modeling of liquid density data was performed by the perturbed-chain statistical associating fluid theory (PC-SAFT) Equation of State and the Tammann-Tait equation with maximum absolute average deviations of 0.15 % and 0.05 %, respectively. Both models were applied for correlating the thermodynamic derived properties of the fluid phase: isobaric thermal expansivity and isothermal compressibility.

Comprehensive data-driven methods for estimating the thermal conductivity of biodiesels and their blends with alcohols and fossil diesels

Biodiesels offer viable alternatives to fossil diesels as renewable and clean energy sources. Understanding the thermal conductivity of biodiesels is crucial for engine design and heat transfer rate calculations in thermal systems. However, existing literature lacks validated predictive tools for this property. To address this, a study utilized 2552 data points from 18 published studies with uncertainties less than 2 %, covering 26 fatty acid alkyl ester biodiesels, 12 biodiesel-alcohol mixtures, and 9 biodiesel-fossil diesel blends across various pressure and temperature conditions. Three machine learning algorithms were employed, using input variables of reduced temperature, reduced pressure, and average molecular weight. Models were trained on 80 % of the data and evaluated on the remaining 20 %. Statistical error metrics and graphical analysis confirmed high precision in predicting biodiesel thermal conductivity. The Gaussian Process Regression model showed the best consistency, with an average absolute relative error (AARE) of 0.36 % and determination coefficient (R2) of 99.69 % on the testing dataset. These models were versatile, applicable to different biodiesel mixtures, accurately capturing thermal conductivity behavior under diverse operating conditions. In contrast, existing literature correlations were limited to specific conditions and required complex calculations. Additionally, a sensitivity analysis determined the relative importance of factors influencing thermal conductivity.

Exploring Alkyl Ester Salts of L-Amino Acid Derivatives of Ibuprofen: Physicochemical Characterization and Transdermal Potential.

This research presents novel ibuprofen derivatives in the form of alkyl ester salts of L-amino acids with potential analgesic, anti-inflammatory, and antipyretic properties for potential use in transdermal therapeutic systems. New derivatives of (RS)-2-[4-(2-methylpropyl)phenyl]propionic acid were synthesized using hydrochlorides of alkyl esters (ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, and pentyl) of L-glutamine. These were further transformed into alkyl esters of L-amino acid ibuprofenates through neutralization and protonation reactions. Characterization involved spectroscopic methods, including nuclear magnetic resonance and Fourier-transform infrared spectroscopy. Various physicochemical properties were investigated, such as UV-Vis spectroscopy, polarimetric analysis, thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, water solubility, octanol/water partition coefficient, and permeability through pig skin using Franz diffusion cells. The research confirmed the ionic structure of the obtained hydrochlorides of alkyl esters of L-amino acids and ibuprofenates of alkyl esters of L-glutamic acid. It revealed significant correlations between ester chain length and thermal stability, crystallinity, phase transition temperatures, lipophilicity, water solubility, skin permeability, and skin accumulation of these compounds. Compared to the parent ibuprofen, the synthesized derivatives exhibited higher water solubility, lower lipophilicity, and enhanced skin permeability. This study introduces promising ibuprofen derivatives with improved physicochemical properties, highlighting their potential for transdermal therapeutic applications. The findings shed light on the structure-activity relationships of these derivatives, offering insights into their enhanced solubility and skin permeation, which could lead to more effective topical treatments for pain and inflammation.

Optimization, characterization and properties of biodiesel produced from waste sunflower frying oil

Biodiesel from renewable resources generally produced with the transesterification of vegetal oils or animal fats. In this study, we have improved the reaction conditions of the transesterification of the sunflower oil outcome in from frying. Fatty acid alkyl ester synthesized were characterized by the FT-IR spectroscopy and the CG-SM. For that, a range of experiences have been made in 25 °C and in 50 °C with different types of alcohols and in reaction times going from 30 to 240 minutes. The best result of fatty acid alkyl ester have been obtained at 25°C using methanol as an alcohol after an hour of reaction. Features of the obtained biodiesel under optimal conditions in particular kinematic viscosity, density, the cloud point and the flash point were determined and compared to ASTM D6751 biodiesel standards. The results show that the produced biodiesel lines with the standards and there is no major difference between EEAG and EMAG features.

Assessment of glycerol in biodiesel using an ultrasonic measurement method

Biodiesel is a renewable fuel, biodegradable and alternative to diesel oil consisting chemically of fatty acid alkyl esters and obtained by the transesterification reaction. After transesterification, undesirable components may remain in biodiesel. The presence of these components negatively influences the properties and performance of biodiesel. This research aims to evaluate biodiesel quality, using the quantitative ultrasound technique to determine the presence of the contaminant glycerol in biodiesel samples. The blends used in this study consisted of biodiesel and glycerol varying from 0 % to 0.5 % of glycerol by mass. The measurement uncertainty was evaluated according to the Guide to the Expression of Uncertainty in Measurement. The speed of sound in biodiesel/glycerol blends was measured by the pulse-echo technique (@ 5 MHz) and was considered equivalent for the different concentrations studied. The maximum measurement uncertainty obtained was 2.2 m·s−1 (0.16 %).

Exploring the antioxidant “cut-off effect” of gallic acid alkyl esters in dried oysters (Crassostrea gigas) during storage

In some complex food matrices, lipophenols exert stronger antioxidant effects than free polyphenols due to their better amphiphilicity and solubility. The use of lipophenols of different chain lengths often presents a “cut-off effect” in real foods, but the reason is far from understood. This work compared the antioxidant capacity of ethyl gallate (EG), octyl gallate (OG) and myristyl gallate (MG) in dried oysters during storage. The oxidation rate of polyunsaturated fatty acids (PUFAs), oxidation inhibition rate of the antioxidants on PUFAs and the generation number of lipid hydroperoxides and aldehydes shown that the treatment of antioxidants effectively inhibited lipid oxidation during storage, and the inhibition ability in the OG group was significantly better than that in the other antioxidant groups, which was consistent with the as of the “cut-off effect”. The density functional theory (DFT) and the molecular dynamics (MD) simulation showed that this “cut-off effect” is related to the ability of the polyphenolic hydroxyl group at C4 to transfer hydrogen atoms and the effective concentration of lipophenols at the initiation site of lipid oxidation.

Influence of Molecular Structure on the Physicochemical and Tribological Properties of Biolubricants: A Review

The increase in the price of crude oil, the environmental impact, or the depletion of fossil resources has increased the need for bio-based alternatives. This has led to the search for renewable, biodegradable, and environmentally friendly raw materials to obtain lubricants that meet these characteristics. This review deals with the state of the art of biolubricants along with their most common raw materials and molecular structures, processes of chemical modification of bio-oils, as well as the relationship between their structural features and physicochemical/tribological properties. This review concludes that the production of fatty acid alkyl esters from vegetable oils is the most promising chemical route to produce a wide range of biolubricants through double transesterification reactions. It also highlights the need to explore this route for the production of microalgae-derived biolubricants due to its environmental benefits during cultivation and production processes.

Road dust resuspension in a coastal Atlantic intermunicipal urban area with industrial facilities: Emission factors, chemical composition and ecotoxicity

Road dust resuspension in urban environments can be both a means of transport of pollutants across the various environmental compartments and a source of pollutants itself, becoming a potential threat to human health. With the aim of obtaining emission factors and achieving a detailed chemical characterisation of road dust (RD) in typical Portuguese cities, a sampling campaign was performed in the region of Aveiro. Locations were chosen for intercomparison in various urban environments with different land uses, from the busier city centre and university campus to residential neighbourhoods and harbour-commercial areas with industrial activities. PM10 samples were analysed for organic and elemental carbon (OC and EC) by a thermal-optical technique, elemental composition by PIXE, organic speciation by GC–MS, and ecotoxicology by a luminescence inhibition bioassay with Aliivibrio fischeri. A health risk assessment for elements and PAHs was carried out. Dust loadings of 1.9 ± 1.8 mg PM10 m−2 were registered overall, whereas in the most trafficked areas of city centre they reached more than three times the average. OC accounted for 6.5–15.5% of total PM10, but element oxides represented the largest mass fraction (61.4 ± 8.6%). A strong enrichment was detected mostly for typical traffic-related elements such as Cu, Zn, As, Br, Cr, Ni and Mo and interestingly, Rb and Se. The analysed organic compounds accounted for 3.66–11.0 mg g−1 PM10, including PAHs and aliphatics, with a clear dominance of plasticisers. Some other compounds attributed to non-vehicle sources, such as fatty acid alkyl esters, were also detected. As concerns the 16 priority PAHs, their total mass concentration ranged from 5.58 to 36.3 μg g−1 PM10, with clear variability between sampling spots. All samples caused an ecotoxicological reaction in the bioassay, but samples from harbour and commercial areas proved to be most toxic.

Biodiesel Production from Sal Oil: A Mamdani-Type Fuzzy Inference System Using the Fuzzy Logic Toolbox Graphical User Interface (Gui) Tools

This paper describes the performance evaluation of fuzzy logic controller in Biodiesel Production system using MATLAB Simulink and MATLAB Fuzzy Logic Toolbox. Biodiesel (fatty acid alkyl esters) is derived from triglycerides by transesterification with alcohol, has attracted considerable attention during the past decade as a renewable, biodegradable, and nontoxic fuel. Vegetable oils are produced from numerous oil seed crops and many of them are used for edible purpose. The oil obtained from Sal seeds (Shorea Robusta) even though used by local tribes in Indian forests for edible purpose, it is still classified as non-edible oil. Sal tree is abundantly available in forests of Indian subcontinent and this wood is used in building construction and manufacture of furniture because of its characteristic hardness. In this paper maximum output yield-Biodiesel Production has been done (SOME-Sal Oil Methyl Esters) by optimizing reaction parametersin relation to the Excess Methanol Quantity (EMQ, 150%),Reaction Temperature (RT, 65°C), Catalyst Quantity (CQ, NaOH - 0.25 W%) by Max-Min (MAMDANI) Method Fuzzy Inference System using the Fuzzy Logic Toolbox Graphical User Interface (GUI) Tools of MATLAB (Intelligent System).

Tailoring Synthetic Pelargonic Acid Esters for Bio-Based Lubricant Applications: Exploring the Relationship between Structure and Properties.

Pelargonic acid (PA) is commercially obtained by oxidative cleavage of fatty acid double bonds. Its esters are interesting compounds used to create bio-based products. An industrially relevant application of these compounds is in the field of solvent manufacturing and formulation of green lubricating oils. The physical-chemical and rheological properties of these esters are influenced by the structural features of the alcohol used as starting materials, such as chain length, number of unsaturation, and degree of branching. This work provides an in-depth study of the existing structure-properties relations for fatty acid alkyl esters obtained from PA and different alcohols [i.e., 2-ethylhexanol (EtHex), ethylene glycol, 1,3-propanediol, 1,4-butanediol, trimethylolpropane, and pentaerythritol]. The aim is to evaluate the use of the synthesized product for the formulation of bio-based lubricants. The chosen alcohols are frequently employed in the preparation of bio-based lubricants. In addition, most of them, such as EtHex and diols, can be derived from biomass sources, contributing to the sustainability of the obtained products. For comparison purposes, some of these alcohols were also used for the synthesis of the corresponding oleic acid esters, which were chosen as a benchmark due to their common use in the synthesis of bio-based lubricants. The influence of the structural factors on the viscosity, pour point (PP), and oxidation stability of the synthesized esters was highlighted by comparing the obtained results. Pelargonates showed lower viscosities and higher PPs than that of the oleates, but they present high stabilities to the oxidation due to the absence of unsaturation.

Evaluation of the flammability characteristics of alkyl esters: New QSPR models

In the present study, new quantitative structure–property relation (QSPR) models have been developed to predict different flammability characteristics (i.e., Lower flammability temperature (LFLT), Upper flammability temperature (UFLT), Lower flammability percent (LFL(V%), and Upper flammability percent (UFL(V%)) of pure Alkyl esters. In this regard, new data sets containing 179 different alkyl esters from 10 different chemical categories were used. In the model development procedure, the appropriate molecular descriptors were selected for each property using the enhanced replacement method (ERM). Afterward, a multivariable linear model and three nonlinear models based on genetic programming (GP), random forest regression (RFR), and support vector regression (SVR) were developed using the molecular descriptors as input variables. The implementation of different internal and external validation methods confirmed the acceptable prediction capability of the developed models. In this regard, the average absolute error for the best models were 7.61 K for LFLT, 7.96 K for UFLT, 0.10 % for LFL (V%), and 1.10 for UFL(V%) over the whole dataset. A comparison between the prediction capabilities of the developed QSPR models with previous models also confirmed the superiority of the developed models in this study. Therefore, the developed QSPR models can be employed in the evaluation of the flammability characteristics of new alkyl esters such as new fatty acid alkyl esters in the biodiesel.

Intensification and Optimization of FAME Synthesis via Acid-Catalyzed Esterification Using Central Composite Design (CCD).

The acid-catalyzed pre-treatment esterification process is required for low-cost feedstock with high free fatty acids (FFAs) to avoid the saponification that occurs during alkali-catalyzed transesterification for the production of fatty acid alkyl esters (FAAE). Reverse hydrolysis in acid-catalyzed esterification causes a decrease in fatty acid methyl ester (FAME) yield. Therefore, the esterification process must be intensified. This study aims to develop and optimize a low-temperature intensification process to enhance biodiesel yield and reduce energy consumption. Three intensification systems were studied: co-solvent technique, co-solvent coupled with adsorption of water using molecular sieves, and entrainer-based continuous removal of water. The process variables of esterification reaction in co-solvents without the adsorption system were optimized by using central composite design (CCD). The study showed that the co-solvent without the adsorption system was effective in intensifying the FFA conversion (XFFA) at low temperatures, compared to the other two systems, due to the dilution effect at high co-solvent/entrainer amount required for sufficient vapors in the adsorption system. Optimized process variables have achieved 95% XFFA within 75 min at 55 °C, 20 mL/100 g of oil DEE, 9 MR, 3 wt % H2SO4, and 320-350 RPM in a co-solvent without the adsorption system.

Chemical and Biological Profiling of Three Ferulic Acids Alkyl Esters Isolated from Jatropha pandurifolia (Family: Euphorbiaceae) Stem Bark.

The study's objectives include phytochemical profiling and biological (antioxidant, thrombolytic and cytotoxic) analysis of pure chemicals from Jatropha pandurifolia stem bark ethyl acetate extract. Five different compounds including octacosanyl cis ferulate (1), hexacosyl (E)-ferulate (2) triacontyl ferulate (3), β-sitosterol (4) and stigmasterol (5) are elucidated. Their structures determine through 1HNMR analysis and comparison to published data, while three ferulic acid alkyl esters (1-3) were isolated for the first time from J. pandurifolia. Compounds 1, 2, and 3 all have significant thrombolytic potential with respective values of 68.92% ±1.17 (**P<0.01), 66.56% ±2.35 (**P<0.01) and 70.81%±0.98 (**P<0.01) with comparison to standard streptokinase (73.6%±0.76). When compared to BHT (6.82± 0.99 μg/ml) the IC50 (DPPH assay) values were 16.26±1.07 (**P<0.01), 14.12±1.23 (**P<0.01), and 13.16±1.70 μg/ml (**P<0.01). Comparing the three compounds to the reference vincristine sulphate (LC50: 0.52±0.18 μg/ml), of compound 1 (1.56±0.35 μg/ml) (**P<0.01), compound 2 (1.3±0.78 μg/ml) (**P<0.01) and compound 3 (1.29±0.33 μg/ml) (**P<0.01). The results can therefore be interpreted as a concept of isolated molecules having potential for application in additional pharmaceutical research.

Sample preparation of free sterols from vegetable oils by countercurrent chromatography in co-current mode

Countercurrent chromatography (CCC) is a preparative instrumental method where both the mobile and stationary phases are liquids and which are predominantly used for the isolation of natural products. In this study, we widened the scope of CCC by using it as an instrumental method for the direct enrichment of the free sterol fraction from plant oils to which they contribute with ~ 1%. For the enrichment of sterols in a narrow band, we employed the so-called co-current CCC (ccCCC) mode in which both liquid phases of the solvent system (here: n-hexane/ethanol/methanol/water (34:11:12:2, v/v/v/v)) are moved at different flow rates in the same direction. Different from previous applications of ccCCC, the lower and predominant “stationary” phase (LPs) was pumped twice as fast as the mobile upper phase (UPm). This novel reversed ccCCC mode improved the performance but also required a higher demand of LPs compared to UPm. Therefore, the exact phase composition of UPm and LPs was determined by gas chromatography and Karl Fischer titration. This step enabled the direct preparation of LPs which considerably reduced the waste of solvents. Internal standards (phenyl-substituted fatty acid alkyl esters) were synthesised and utilised to frame the free sterol fraction. This approach allowed a fractionation of free sterols based on the UV signal and compensated run-to-run variations. The reversed ccCCC method was then applied to the sample preparation of five vegetable oils. In addition to free sterols, free tocochromanols (tocopherols, vitamin E) were also eluted in the same fraction as free sterols.Graphical