Esterification Step Research Articles

Synthesis of a natural core substrate with lignin-xylan cross-linkage for unveiling the productive kinetic parameters of glucuronoyl esterase

Lignin-carbohydrate complexes (LCCs) present a considerable hurdle to the economic utilization of lignocellulosic biomass. Glucuronoyl esterase (GE) is an LCC-degrading enzyme that catalyzes the cleavage of the cross-linkages between lignin and xylan in LCCs. Benzyl-d-glucuronate (Bn-GlcA), a commercially available substrate, is widely used to evaluate GE activity assays. However, since Bn-GlcA lacks the structural backbone of naturally occurring LCCs, the mechanisms underlying the activity of GEs and their diversity in the structure-activity relationship are not fully understood. Herein, we provided a synthesis scheme for designing 1,23-α-d-(6-benzyl-4-O-methyl-glucuronyl)-1,4-β-d-xylotriose (Bn-MeGlcA3Xyl3) as a natural core substrate bearing cross-linkage between lignin and glucuronoxylan. A well-defined and yet more realistic synthetic substrate was successfully synthesized via a key step of the benzyl esterification of 4-O-methyl-glucuronyl-1,4-β-d-xylotriose (MeGlcA3Xyl3), a minimized fragment of glucuronoxylan enzymatically digested by β-1,4-xylanase. To the best of our knowledge, this is the first report of the productive GE kinetic analysis using this substrate. Kinetic parameters of the GE from the fungal Pestalotiopsis sp. AN-7 (PesGE), i.e., the Km, Vmax, and kcat of Bn-MeGlcA3Xyl3, were 0.43 mM, 55.5 μmol min−1·mg−1, and 35.8 s−1, respectively. On the other hand, as reported to date, the productive kinetic parameters for Bn-GlcA were not obtained because of its excessively high Km value (>16 mM). The substantial variance in the enzymatic activity of PesGE regarding substrate-binding affinity between Bn-MeGlcA3Xyl3 and Bn-GlcA was also demonstrated using in silico docking simulation. These results suggested that the extended xylan fragment is a key structural determinant affecting PesGE's substrate recognition. Furthermore, the presence of a natural xylan backbone allows for evaluating the enzyme activity of xylan-degrading enzymes. Accordingly, the synthesized substrate with the natural core structure of LCC allowed us to unveil the productive kinetic parameters of GEs, serving as a versatile substrate for further elucidating the cascade reaction of GE and xylan-degrading enzymes.

Antimigratory Effect of Lipophilic Cations Derived from Gallic and Gentisic Acid and Synergistic Effect with 5-Fluorouracil on Metastatic Colorectal Cancer Cells: A New Synthesis Route.

Colorectal cancer (CRC) is the third leading cause of cancer deaths in the world. Standard drugs currently used for the treatment of advanced CRC-such as 5-fluorouracil (5FU)-remain unsatisfactory in their results due to their high toxicity, high resistance, and adverse effects. In recent years, mitochondria have become an attractive target for cancer therapy due to higher transmembrane mitochondrial potential. We synthesized gallic acid derivatives linked to a ten-carbon aliphatic chain associated with triphenylphosphonium (TPP+C10), a lipophilic cationic molecule that induces the uncoupling of the electron transport chain (ETC). Other derivatives, such as gentisic acid (GA-TPP+C10), have the same effects on colorectal cancer cells. Although part of our group had previously reported preparing these structures by a convergent synthesis route, including their application via flow chemistry, there was no precedent for a new methodology for preparing these compounds. In this scenario, this study aims to develop a new linear synthesis strategy involving an essential step of Steglich esterification under mild conditions (open flask) and a high degree of reproducibility. Moreover, the study seeks to associate GA-TPP+C10 with 5FU to evaluate synergistic antineoplastic effects. In addition, we assess the antimigratory effect of GA-TPP+C10 and TPP+C10 using human and mouse metastatic CRC cell lines. The results show a new and efficient synthesis route of these compounds, having synergistic effects in combination with 5FU, increasing apoptosis and enhancing cytotoxic properties. Additionally, the results show a robust antimigratory effect of GATPP+C10 and TPP+C10, reducing the activation pathways linked to tumor progression and reducing the expression of VEGF and MMP-2 and MMP-9, common biomarkers of advanced CRC. Moreover, TPP+C10 and GA-TPP+C10 increase the activity of metabolic signaling pathways through AMPK activation. The data allow us to conclude that these compounds can be used for in vivo evaluations and are a promising alternative associated with conventional therapies for advanced colorectal cancer. Additionally, the reported intermediates of the new synthesis route could give rise to analog compounds with improved therapeutic activity.

A hydroesterification reaction system to produce octyl esters using degummed soybean oil as substrate: Combining reusable free and immobilized lipases

This study shows the enzymatic synthesis of octyl alcohol-based biolubricants carried out in two catalytic steps: degummed soybean oil (DSO) hydrolysis and esterification of the produced and purified free fatty acids (FFA). Several lipases were evaluated as catalysts in the hydrolysis of DSO. Under optimal conditions, lipase from Pseudomonas fluorescens (PFL) yielded 97 % conversion after 23 h using 50 U/g oil and DSO:water mass ratio of 1:0.5. Sequential batch strategies have been developed for the recovery and reuse of free enzyme in further hydrolysis cycles. When hexane was used in the separation between the FFA-rich phase and the phase composed of water, enzyme and glycerol, there was better PFL recovery and FFA-conversion of 65 % was still achieved after five 24-hour hydrolytic cycles. In the esterification step, the potential of four lipases (commercial Lipozym-435, and lipase B from Candida antarctica (CALB), lipase from porcine pancreas (PPL) and Eversa® Transform 2.0 (EV) immobilized on Purolite Lifetech EC8806F) were evaluated in the production of octyl esters in a solvent-free medium (FFA/octanol molar ratio of 1:2.5) using screw-capped glass bottles as reactor. The immobilized EV gave the best ester yield (∼87 wt%). When EV-Purolite was used in a vortex flow reactor, a yield of around 94 wt% was reached after 3 h of reaction using a biocatalyst load of 1 % (w/v) and FFA/octanol molar ratio of 1:2.5. The immobilized lipase could be reused for five consecutive 3 h-batches of esterification, maintaining the octyl esters yield of the first batch.

Catalytic Cleavage of the 9-Fluorenylmethoxycarbonyl (Fmoc) Protecting Group under Neat Conditions.

This work reports the first solvent-free catalytic approach for the cleavage of the fluorenylmethoxycarbonyl (Fmoc) protecting group from amine and alcohol functionalities. Various saccharide, peptide, and glyco-amino acid substrates were efficiently deprotected by simple treatment with 20 mol % neat 4-dimethylaminopyridine (DMAP) (one of the effective base catalysts found), without any solvent or stoichiometric additives. Small model structures were finally assembled through one-pot, base-catalyzed, solvent-free multistep sequences combining the Fmoc cleavage with esterification, amidation, and/or glycosylation steps.

A Protection Strategy for High‐yield Synthesis of Dimethyl Furan‐2,5‐dicarboxylate from 5‐Hydroxymethylfurfural Using Methanol as an Acetalizing Agent

AbstractDeveloping efficient catalytic processes for obtaining biobased monomers for plastics can significantly contribute to a more sustainable economy. The biomass‐derived and chemical platform 5‐hydroxymethylfurfural (HMF) can be converted to various key intermediates, which is often hampered by side reactions due to the reactive nature of the formyl group in HMF. Here, we present a stepwise approach involving a protecting agent to obtain dimethyl furan‐2,5‐dicarboxylate (MFDC), which is a monomer for polyalkylene furanoates, a new class of biobased polyesters. Methanol is used as a solvent, reactant, and protecting agent for HMF's formyl group. In the first step, the oxidative esterification of the hydroxymethyl group to methyl carboxylate in HMF‐dimethylacetal catalyzed by Au/CeO2 affords methyl 5‐formylfuran‐2‐carboxylate dimethylacetal (MFFC‐acetal) in high yields (>90 %) from concentrated methanolic solutions (~20 wt %). Without protecting agent, a mixture of methyl‐5‐hydroxymethylfuran‐2‐carboxylate (MHMFC), MFDC, and humin byproduct was obtained. The deprotection of MFFC‐acetal in the second step proceeded efficiently in acetone with Amberlyst‐15, affording MFFC in a >90 % yield. In the final step, oxidative esterification of MFFC in methanol (10 wt %) afforded MFDC in a 93 % yield using Au/CeO2. The acetal protection strategy with methanol offers an efficient route toward MFDC in two oxidative esterification steps.

Experimental and Simulation Analysis to Predict the Optimum Biodiesel Yield from Two Different Feedstock Using Heterogenous Base Catalyst

Abstract: Biodiesel can be easily used an alternative fuel. Using the Soxhlet apparatus, the oil waas extracted, and centrifuged to separate the oil. The physical characteristics of oil was determined. A number of >3 indicates an acid, while a value < 3 indicates a base. If the FFA content is >0.5, the substance is an acid, and if it’s less than 0.5, a base. Suitable solvent based on its physicochemical characteristics was selected. In this study two types of seeds were used. A mixed heterogeneous base catalyst containing CaO prepared from waste egg shells andcockle shells. The egg shells and cockle shells were dried in microwave oven for 24 hours at 120◦C and placed in Muffle furnace at 900 ◦C and mixed in 1:1 ratio. SEM, EDAX and FTIR were used to characterize the catalyst. The two feedstock used in this study was Solanum Torvum and Murraya Koenigii. Double Step Esterification was preferred. The oil was treatedwith the strong acid H2SO4 . Then oil along with methanol was treated with both acid and basecatalyst separately to give Fatty Acid Methyl Ester. Finally optimum condition was found for maximum yield of FAME, was obtained using RSM.

Application of molecular distillation in the recovery of high-value bioactive compounds present in wastes of vegetable oil processing: effect of esterification

Refining vegetable oils generate residues that can be reused to obtain high-value compounds. Tocopherols, phytosterols, and squalene can be recovered from deodorizer distillates using molecular distillation. However, treatment of the deodorizer distillates is required to obtain better separation results. Thus, this work aimed to evaluate the effect of the esterification of a residue composed of mixtures of different types of deodorizer distillates on the efficiency of phytonutrient recovery by molecular distillation. The results showed the best conditions for the esterification were 74 °C, 214 min, 3% H2SO4, and 2:1 molar methanol/free fatty acids ratio. These reaction conditions maintained 97% of total phytonutrients and reduced 90.5% of free fatty acids. Concentration gains for tocopherols (331%), phytosterols (232%), and squalene (300%) were obtained for the esterified residue. Therefore, this work presents an alternative route to obtaining a phytonutrient concentrate by combining steps of esterification and molecular distillation for mixtures of deodorizer distillates.

Functional Lignin Building Blocks: Reactive Vinyl Esters with Acrylic Acid.

Introducing vinyl groups onto the backbone of technical lignin provides an opportunity to create highly reactive renewable polymers suitable for radical polymerization. In this work, the chemical modification of softwood kraft lignin was pursued with etherification, followed by direct esterification with acrylic acid (AA). In the first step, phenolic hydroxyl and carboxylic acid groups were derivatized into aliphatic hydroxyl groups using ethylene carbonate and an alkaline catalyst. The lignin was subsequently fractionated using a downward precipitation method to recover lignin of defined molar mass and solubility. After recovery, the resulting material was then esterified with AA, resulting in lignin with vinyl functional groups. The first step resulted in approximately 90% of phenolic hydroxyl groups being converted into aliphatic hydroxyls, while the downward fractionation resulted in three samples of lignin with defined molar masses. For the esterification reaction, the weight ratio of reagents, reaction temperature, and reaction time were evaluated as factors that would influence the modification efficacy. 13C NMR spectroscopy analysis of lignin samples before and after esterification showed that the optimized reaction conditions could reach approximately 40% substitution of aliphatic hydroxyl groups. Both steps only used lignin and the modifying reagent (no solvent), with the possibility of recovery and reuse of the reagent by dilution and distillation. An additional second esterification step of the resulting lignin sample with acetic acid or propionic acid converted 90% of remaining hydroxyl groups into short-chain carbon aliphatic esters, making a hydrophobic material suitable for further copolymerization with synthetic hydrophobic monomers.

Macrocyclization strategies for the total synthesis of cyclic depsipeptides.

Cyclic depsipeptides are an important class of peptide natural products that are defined by the presence of ester and amide bonds within the macrocycle. The structural diversity of depsipeptides has required the development of a broad range of synthetic strategies to access these biologically active compounds. Solid phase peptide synthesis (SPPS) strategies have been an invaluable tool in their synthesis. The key aspect of their synthesis is the macrocyclization strategy. Three main strategies are used, solution phase macrolactamization of acyclic ester containing peptide, on-resin macrolactamization of a sidechain-anchored peptide, and the solution phase macrolactonization of a linear peptide. Additionally, biocatalysts have been used to produce these compounds in a regio- and chemo-selective manner. Each compound offers unique challenges, requiring careful synthetic design to avoid undesirable side reactivity or unwanted epimerization during the esterification and macrocyclizing steps. This focused review analyzes these three strategies for cyclic depsipeptide natural product total synthesis with selected examples from the literature between 2001-2023.

VALIDATION OF AN ANALYTICAL METHOD FOR THE DETERMINATION OF FATTY ACIDS IN SHEEP BLOOD SERUM SAMPLES

Low-density dispersive liquid-liquid microextraction with a subsequent esterification step was proposed in this study for the determination of linoleic acid and stearic acid in sheep blood serum samples. The method developed aimed to quickly and efficiently extract and esterify both fatty acids with subsequent analysis by gas chromatography/flame ionization detection. The extraction method was optimized with Scheffé’s polynomial model for three-component mixtures. The method was validated according to the parameters established by Eurachem Guide (2014). The optimal extraction conditions for LD-DLLME were 1400 µL of dispersion medium (MgCl2 0.017%), 400 µL of extractor solvent (toluene) and 1200 µL of dispersion solvent (methanol). The method performance showed adequate selectivity, sensitivity and precision to be applied to real samples, with an average recovery of 98.54% for linoleic acid and 103.83% for stearic acid. LD-DLLME was superior to the traditional method of analysis, which has been used until now for the determination of fatty acids in blood serum samples from ruminants. The analysis of real samples showed that the developed method is efficient for monitoring these substances in ruminants.

Obtaining hydrolysate from macauba oil and its application in the production of methyl esters

This work aimed to obtain a hydrolyzate rich in free fatty acids (FFA) from the hydrolysis of macauba oil for subsequent esterification and obtaining of methyl esters. To determine the conditions that maximize FFA yield in the hydrolysis step, the effects of buffer solution percentage and catalyst concentration (Lipozyme® RM IM) were determined at 55 ºC and 6 h. From the results, it was verified that both variables evaluated in the experimental range had an influence on the reaction and their increase favored the production of FFA. Additional experiments were carried out to assess the influence of reaction time with a progressive increase up to 8 h. Hydrolyzate with ~92 wt % FFA was obtained and its use in the enzymatic esterification step using Novozym® 435 as catalyst resulted in ~95 % FFA conversion. Regarding the reuse of enzymes at each stage, a ~50 % reduction in FFA yield was found and only 98 % FFA conversion.

A Theoretical and Experimental Study for Enzymatic Biodiesel Production from Babassu Oil (Orbignya sp.) Using Eversa Lipase

A theoretical and experimental study was carried out on the biocatalytic production of babassu biodiesel through enzymatic hydroesterification. The complete hydrolysis of babassu oil was carried out using a 1:1 mass solution at 40 °C for 4 h using 0.4% of lipase from Thermomyces lanuginosus (TLL). Then, with the use of Eversa® Transform 2.0 lipase in the esterification step, a statistical design was used, varying the temperature (25–55 °C), the molar ratio between free fatty acids (FFAs) and methanol (1:1 to 1:9), the percentage of biocatalyst (0.1% to 0.9%), and the reaction time (1–5 h) using the Taguchi method. The ideal reaction levels obtained after the statistical treatment were 5 h of reaction at 40 °C at a molar ratio of 1:5 (FFAs/methanol) using 0.9% of the biocatalyst. These optimal conditions were validated by chromatographic analysis; following the EN 14103 standard, the sample showed an ester concentration of 95.76%. A theoretical study was carried out to evaluate the stability of Eversa with FFAs. It was observed in the molecular docking results that the ligands interacted directly with the catalytic site. Through molecular dynamics studies, it was verified that there were no significant conformational changes in the studied complexes. Theoretical and experimental results show the feasibility of this process.

Synthesis of energy rich fuel additive from biomass derived levulinic acid and furfuryl alcohol using novel tin-exchanged heteropoly acid supported on titania nanotubes as catalyst

Biomass feedstocks are available in a wide variety. It is an alternative source to fossil fuels to meet higher energy demand and a renewablefeedstock for many industrial products and chemical substances. Furfuryl alcohol and levulinic acid are both biomass-based chemicals that can be valorized for use in various applications. In the current study, we have introduced esterification reaction of furfuryl alcohol with levulinic acid to produce furan-2-ylmethyl 4-oxopentanoate, which can be used to synthesize biofuels, perfumes, flavouring agents, and other industrially useful compounds. For this conversion, a novel and highly efficient catalyst, 20 % (w/w) Sn metal exchanged dodecatungstophosphoric acid (TPA) with titania nanotubes (TNT) support was used under environmentally benign solventless reaction conditions. Partially substituted protons of TPA with Sn (x = 1) increased the acidity of the catalyst, and resulted into higher activity than 20 % (w/w) TPA/TNT. Protons of TPA were substituted with Sn metal at different proportions (i.e., H = 1, 2, 3 of TPA exchanged with Sn = 0.5, 1, 1.5, respectively). Amongst all, 20 % (w/w) Sn1-TPA/TNT was found to be the most efficient catalyst for the esterification reaction of furfuryl alcohol and levulinic acid due to its higher acidity. Fresh and reused catalysts were well-characterized using various analytical techniques. Using LHHW (Langmuir–Hinshelwood–Hougen–Watson) mechanism, a kinetic model was developed. The activation energy was found to be 7.85 and 13.58 kcal/mol for esterification (step 1) and self-etherification (step 2) reactions, respectively. The activation energy of esterification is lower than that of self-etherification and the rate of esterification is higher than that of self-etherification.

Synthesis of MgO/MgSO4 nanocatalyst by thiourea–nitrate solution combustion for biodiesel production from waste cooking oil

A novel MgO/MgSO4 nanocatalyst was synthesized using solution combustion method with thiourea as the fuel. The in-situ inducement of sulfonated group over the basic catalyst, MgO, was carried out for the first time using thiourea for the production of biodiesel. The synthesized nanocatalyst with its bi-functional characteristics performed efficiently in the simultaneous transesterification and esterification of high free fatty acid (FFA) containing waste cooking oil (WCO) into biodiesel in the presence of ultrasound. The newly developed nanocatalyst was characterized by XRD, FESEM, EDS, FTIR and BET analyses. The resulting nanocatalyst possesses a specific surface area of 82 m2/g and a pore volume of 0.047 cm3/g. The high sulfur content of 13.65% of the novel catalyst developed facilitates its high acidic characteristics suitable for the esterification step. The optimization of the process carried out by the response surface methodology (RSM) predicted the optimized parameters as follows: methanol to oil molar ratio-9.4:1, catalyst loading-8.9 wt%, ultrasonic power-402 W and reaction time-46 min. The optimum yield of biodiesel predicted by the RSM was 98.8%. The synthesized nanocatalyst demonstrated high stability which established significant future perspective for industrial production of biodiesel from low cost, high FFA containing feedstock.

Pongamia pinnata biodiesel production using cobalt doped ZnO nanoparticles—An analytical study

AbstractKaranja is second most popular non‐edible oil, in Indian sub‐continent, for Biodiesel production; with current plantation, almost 55,000 ton/year of oil can be extracted. Also, studies in past two decades have elucidated that use of heterogeneous solid catalyst has been commercially most viable, economical, produces almost pure biodiesel, easy to use, recycle and environment friendly. In this paper, we have used cobalt doped zinc oxide (CZO) nanoparticles for dual step esterification—transesterification processes, which has not been studied for Karanja oil, additionally, the detailed analytical study such as X‐ray diffraction, field emission scanning electron microscope, Brunauer–Emmett–Teller and energy‐dispersive analysis of X‐rays on catalyst unavailable in literature, has also been incorporated here. The CZO particles are synthesized using co‐precipitation method and yields particles of size ~75 nm, the reusability of catalyst is also included. The optimum process parameters where experimentally determined and compositional analysis of oil and biodiesel is done using Fourier transformed infrared. The economic and technical aspects of CZO synthesis, the benefits of easy separation of glycerol and reduced impurities in final product, make this process commercially more suitable for Karanja oil biodiesel synthesis, and study will promote use of CZO nanoparticles for other oil biodiesel production too. Result shows that under optimized condition of transesterification, 1:25 M ratio of oil:methanol, 0.3 wt% catalytic concentration, 70°C reaction temperature, 180 min time of reaction and 500 rpm of stirring speed fatty acid methyl ester (biodiesel) conversion was 98.5 ± 0.5%.

Zr‐Containing UiO‐66 Metal‐Organic Frameworks as Highly Selective Heterogeneous Acid Catalysts for the Direct Ketalization of Levulinic Acid

AbstractZr‐containing UiO‐66 materials are active and reusable heterogeneous catalysts for the selective ketalization of levulinic acid (LA) with 1,2‐propanediol, affording selectivities of up to 91–93% at full LA conversion, with very low levels of ester or ketal–ester byproducts. This allows the preparation of the target ketal directly from LA and avoiding intermediate esterification steps of LA to levulinate esters to minimize the formation of unwanted side products. The catalytic activity of UiO‐66 is found to depend critically on the hydration degree of the solid and the amount of missing linker defects. The most likely active sites for ketalization in (defective) UiO‐66 are Brønsted‐induced acid sites arising from the strong coordination and polarization of H2O molecules onto accessible Zr4+ associated with missing linker defects. A progressive deactivation is observed upon catalytic reuse, which is attributed to adsorbed reaction products poisoning the catalytic sites. These adsorbed products are easily removed by washing the spent catalyst with a dilute 2% HCl ethanolic solution, which completely restores the initial catalytic activity while maintaining the crystallinity of the solid intact.

Structure‐Performance Guided Design of Sustainable Plasticizers from Biorenewable Feedstocks

AbstractThe search for more sustainable solutions for plastics production, moving away from petrochemical feedstocks as today's major raw material basis, is a research area of increasing interest. This task goes far beyond the issue of designing greener polymers and their related monomers as tailor‐made plastics require, besides the polymer itself, further components. These additives also need to be switched from typically fossil‐based to bio‐renewable raw materials. One of such necessary components for many applications are plasticizers, and a major application of them is related to polyvinyl chloride (PVC) as one of the leading polymers with a wide range of applications. Typically today‘s plasticizers are based on fossil feedstocks, and some of them such as specific ortho‐phthalates as the most important product class of plasticizers are now subject to restrictions and authorization by the EU's REACH legislation due to their toxicological profile. In this contribution, we report the synthesis and technical evaluation of alternative, novel bicyclic plasticizer candidates, which are fully accessible from renewable feedstocks. In detail, these new plasticizer target molecules are based on the use of the furan‐derivative 2‐methylfuran, maleic anhydride and 2‐ethylhexanol as bio‐based starting materials. The synthetic concept consists of an initial Diels‐Alder reaction with 2‐methylfuran and a subsequent hydrogenation and optional esterification step. The applied reactions are well‐known as economic and sustainable technologies. Thus, not only the starting materials (being of bio‐based origin) but also the selected reaction technologies for the syntheses of the target molecules are sustainable. Furthermore, a range of performance tests enabled an insight into structure‐performance relationships and revealed promising plasticizing properties of this new bio‐based plasticizer generation with, e. g., an attractive solution temperature fulfilling the criterium for a “fast fuser” as well as good compatibility with PVC.

Synthesis of symmetrical structured triglycerides via a bottom-up process

The synthesis of symmetrical structured triglycerides (STG) through a bottom-up approach was previously shown to produce 1,3-dioleoyl-2-palmitoyl glycerol in significant quantities. This solvent-free lipase-catalyzed process, consisting of a low-temperature (40 °C) esterification step with glycerol dosing followed by a high-temperature (60 °C) esterification step, was further investigated in the production of symmetrical medium-and-long-chain triglycerides (MLCT). By replacing oleic acid with capric acid in the first step or the palmitic acid by either capric acid or lauric acid in the second step, the effects of free fatty chain length and sequence of fatty acid addition on STG production were established. These produced 1,3-dicaproyl-2-oleoyl glycerol, 1,3-dioleoyl-2-caproyl glycerol, and 1,3-dioleoyl-2-lauroyl glycerol at concentrations of 36.98 g, 36.77 g, and 37.08 g per 100 g of triglycerides respectively after 72 h at an overall FFA1:FFA2:Glycerol of 2:1:1 and 4 g Novozyme 435 per 100 g reactants, without the purification of intermediates and products. The sequence of fatty acid addition had the most significant effect as purer STG products can be obtained when the medium chain fatty acid is introduced in the first step. As the process was carried out without solvents, the STG produced are appropriate for functional food or nutraceutical applications.

Study on Synthesis of Solid Acid Catalyst from Borassus flabellifer L. Waste with Sulfonation Method

Fiber of Borassus flabellifer L. includes agricultural wastes which containing lignocellulose components (hemicellulose and lignin) and high carbohydrate content. Siwalan coir fiber is quite potential to be used as a substrate in producing catalysts. Acid catalyst is one type of catalyst that as an important role in chemical process. This study aims to study the effect of the optimum mass ratio of carbon-KOH in the process of graphite synthesis based on siwalan charcoal so as to produce graphite with the most optimal characteristics, and optimum calcination temperature as a physical activation process in the synthesis of graphite based on siwalan coir fiber charcoal, and determine the time sulfonation which is optimum in producing acid catalysts There are 2 variables used in this study, temperature and sulfonation time. The method of making carbon is done by calcining to decompose the carbon source so that the composition is made according to what has been varied. After forming carbon-KOH composite, then sulfonation is carried out using sulfuric acid. The last step is to carry out the esterification step The process in this study discusses carboxylic acid, WCO (Cooking Oil Waste) and methanol (alcohol group).

Hetero-Bis-Conjugation of Bioactive Molecules to Half-Sandwich Ruthenium(II) and Iridium(III) Complexes Provides Synergic Effects in Cancer Cell Cytotoxicity.

Four bipyridine-type ligands variably derivatized with two bioactive groups (taken from ethacrynic acid, flurbiprofen, biotin, and benzylpenicillin) were prepared via sequential esterification steps from commercial 2,2'-bipyridine-4,4'-dicarboxylic acid and subsequently coordinated to ruthenium(II) p-cymene and iridium(III) pentamethylcyclopentadienyl scaffolds. The resulting complexes were isolated as nitrate salts in high yields and fully characterized by analytical and spectroscopic methods. NMR and MS studies in aqueous solution and in cell culture medium highlighted a substantial stability of ligand coordination and a slow release of the bioactive fragments in the latter case. The complexes were assessed for their antiproliferative activity on four cancer cell lines, showing cytotoxicity to the low micromolar level (equipotent with cisplatin). Additional biological experiments revealed a multimodal mechanism of action of the investigated compounds, involving DNA metalation and enzyme inhibition. Synergic effects provided by specific combinations of metal and bioactive fragments were identified, pointing toward an optimal ethacrynic acid/flurbiprofen combination for both Ru(II) and Ir(III) complexes.