Computational and Experimental Studies of Biolubricant Stability Derived from Oleic Acid

In the present work, the stability of six biolubricant compounds, i.e. Acetal, Ketal, D[4.4], D[4.5], Cyclic-6, and Cyclic-7, was evaluated both theoretically and experimentally. These compounds were prepared from oleic acid through hydroxylation and esterification reactions. The computational study of the compounds was conducted by using the Density Functional Theory (DFT) method at B3LYP level of theory and 6-31 G (d,p) basis set. The theoretical stability was reflected from the internal energy value of the hydrolysis reaction of the biolubricant compounds to form the 9,10-dihydroxystearic acid. The order of stability is given as follows: Cyclic-6 (-3.458 kJ/mol) > Acetal (-3.446 kJ/mol) > Cyclic-7 (-3.364 kJ/mol) > D[4.5] (-3.343 kJ/mol) > D[4.4] (-3.261 kJ/mol) > Ketal (-3.058 kJ/mol). On the other hand, the experimental stability of the biolubricant compounds was measured using the American Society for Testing and Material (ASTM) standard method for total acid number (TAN) and total base number (TBN). It was found that the Cyclic-6 derivative yielded the lowest TAN (1.37 mg KOH/g) and TBN (3.53 mg KOH/g) values compared to the other biolubricant compounds. Meanwhile, the Cyclic-6 also showed the lowest internal energy value (-3.458 kJ/mol) from the computational study due to the high stability of six-membered ring. These results reveal that the experimental TAN and TBN values could be predicted from the theoretical internal energy value, i.e. TAN (mg KOH/g) = 35.183 (DE) – 123.02 (R2 = 0.9226) and TBN (mg KOH/g) = 105.71 (DE) – 369.72 (R2 = 0.8946), which is remarkable.

Conversion of Oleic Acid into Azelaic and Pelargonic Acid by a Chemo-Enzymatic Route

A chemo-enzymatic approach for the conversion of oleic acid into azelaic and pelargonic acid is herein described. It represents a sustainable alternative to ozonolysis, currently employed at the industrial scale to perform the reaction. Azelaic acid is produced in high chemical purity in 44% isolation yield after three steps, avoiding column chromatography purifications. In the first step, the lipase-mediated generation of peroleic acid in the presence of 35% H2O2 is employed for the self-epoxidation of the unsaturated acid to the corresponding oxirane derivative. This intermediate is submitted to in situ acid-catalyzed opening, to afford 9,10-dihydroxystearic acid, which readily crystallizes from the reaction medium. The chemical oxidation of the diol derivative, using atmospheric oxygen as a stoichiometric oxidant with catalytic quantities of Fe(NO3)3∙9∙H2O, (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), and NaCl, affords 9,10-dioxostearic acid which is cleaved by the action of 35% H2O2 in mild conditions, without requiring any catalyst, to give pelargonic and azelaic acid.

Identification of α-Glucosidase Inhibitors from Cyperus articulatus L. Rhizome Extract Using HRLC-MS/MS and Molecular Docking

Cyperus articulatus is widely distributed in Indian subcontinent and its rhizome has been used as folk medicine in different geographical regions for treatment of diseases like malaria, epilepsy and dysentery. In present study the rhizome extracts were studied to identify the natural inhibitor compounds for α-amylase and α-glucosidase. Among six different solvent extracts of the rhizome, the acetone extract which showed to have highest phenolics and flavonoids exhibited α-glucosidase inhibition (IC50 9.1 μg/mL). Different fractions were collected using column chromatography and flash chromatography to analyze the active fractions. Two major fractions significantly showed high enzyme inhibitory activity. In HRLC-MS/MS phenolic as well as non-phenolic class of compounds were identified such as quercetrin, dihydroquercetin, mycophenolic acid, koparin-2-methylether, C16-sphinganine, embelin, phytosphingosine, colforsin, 7,8-dihydroxystearic acid and palmitic acid derivative. The two active fractions having IC50 8.38 and 7.65 μg/mL, were shown to exhibit competitive and mixed type inhibition, respectively. Molecular docking analysis of the compounds with the α-glucosidase active site showed that the phenolic class of compounds have efficient binding with one of the aspartate (Asp66, Asp349 and Asp212) residues whereas there was non-polar contacts with other residues in case of non-phenolic compounds such as long chain hydroxyl acids. The results suggest that Cyperus articulatus rhizome is a potential source of drug ingredients for the management of type-II diabetes.

SINTESIS ASAM 9,10-DIHIDROKSI STEARAT (DHSA) MELALUI HIDROLISA EPOKSIDA DARI OKSIDASI ASAM OLEAT DENGAN ASAM PERFORMAT

SYNTHESIS OF 9,10-DIHYDROXYSTEARIC ACID (DHSA) THROUGH HYDROLYSIS EPOXIDE FROM OXIDATION OLEIC ACID AND PERFORMIC ACID. 9,10-dihydroxy stearic acid (DHSA); C18H36O4 is one of hydroxyl fatty acids with hydroxyl groups (OH) and carboxyl groups (-COOH) cause DHSA have unique properties for many applications including as an emulsifier in the oil phase/gel candles and water in cosmetic formulations. This study investigated the formation of DHSA of from oleic acid and performic acid through epoxidation and hydrolysis reactions. Epoxidation was carried out by reacting the oleic acid with formic acid to form performic acid in situ reaction at a temperature of 60-70oC with stirring in order to minimize byproduct, followed hydrolysis obtained DHSA as powder with melting point 86.5oC, iodine value 0.125 g I2/100 g, acid value 171.53 mg KOH/g, the hydroxyl group observed at the absorption band region of 3345.34 cm-1, LCMS analysis results show peak spetrograms-mass at m/z 317,269, with a value m/z is equivalent to molecular weight DHSA. Keywords: DHSA; epoxidation; hydrolysis; hydroxyl fatty acids; oleic acid Abstrak Asam 9,10-dihidroksi stearat (DHSA) dengan rumus molekul C18H36O4 merupakan senyawa hidroksil asam lemak dengan gugus hidroksil (-OH) dan karboksil (-COOH) menyebabkan DHSA memiliki sifat unik untuk berbagai aplikasi antara lain sebagai emulsifier antara fasa minyak/lilin gel dan air dalam formulasi kosmetik. Penelitian ini bertujuan untuk menghasilkan DHSA dari asam oleat dan asam performat, melalui tahapan reaksi epoksidasi dan hidrolisa. Epoksidasi asam oleat dengan asam performat yang dibentuk secara in situ dilakukan pada suhu reaksi 60-70oC dengan pengadukan untuk meminimalkan reaksi samping, dilanjutkan dengan hidrolisa epoksida diperoleh DHSA berupa serbuk berwarna putih gading dengan titik leleh 86,5oC, bilangan iod ± 0,125 g I2/100 g, bilangan asam 171,53 mg KOH/g, gugus hidroksil teramati menggunakan FTIR pada bilangan gelombang 3345,34 cm-1, yang diperkuat dengan data kromatogram LC-MS yang memberikan puncak spektrogram-massa pada m/z 317.269, dengan harga m/z yang setara dengan Berat Molekul DHSA. Kata kunci: DHSA; epoksidasi; hidrolisa; hidroksil asam lemak; asam oleat

Application of Taguchi Optimization Method in Improving the Selectivity of Dihydroxystearic Acid

Dihydroxystearic acid (DHSA) is perceived to be of significant value to various types of industries, especially the oleochemical industry. It is produced by reacting palm-based crude oleic acid (OA) with formic acid and hydrogen peroxide through thein situepoxidation-dihydroxylation, a multistep reaction process. Optimization of the reaction’s operating conditions with respect to the selectivity of DHSA was conducted via the Taguchi method of optimization. The selectivity of DHSA was determined based on gas chromatography (GC) analysis. The signal-to-noise (S/N) ratio analysis procedure in Taguchi method revealed that the optimum operating conditions for the production of crude DHSA with respect to its selectivity were found to be: catalyst (sulphuric acid) loading at 0.5 gm, formic acid-to-oleic acid unsaturation mole ratio of 1:1, hydrogen peroxide-to-oleic acid unsaturation mole ratio of 0.75:1 and reaction temperature: 85°C. ANOVA tested at 90% confidence level revealed that reaction temperature and catalyst loading highly affect the selectivity of DHSA. The selectivity of DHSA was improved to 97.2% by applying the optimum operating conditions as obtained by Taguchi method.