Study of reaction parameters and kinetics of esterification of lauric acid with butanol by immobilized Candida antarctica lipase.

Esterification of lauric acid with n-butanol, catalyzed by immobilized Candida antarctica lipase (CAL) in aqueous-organic biphasic solvent system was studied. Effects of various reaction parameters on esterification were investigated, such as type and amount of solvent, amount of buffer, pH, temperature, speed of agitation, amount of enzyme, butanol and lauric acid. The most suitable reaction conditions for esterification were observed at 50ºC and pH 7.0 using 5000 μmoles of lauric acid, 7000 μmoles of butanol, 0.25 ml phosphate buffer, 1 ml of isooctane as the solvent and 50 mg of immobilized enzyme in the reaction medium at agitation speed of 150 rpm. Maximum esterification of 96.36% was acheived in 600 min of reaction time at n-butanol to lauric acid molar ratio of 1: 0.7. Kinetic study for the esterification of lauric acid with n-butanol using immobilized CAL was carried out and the kinetic constants were estimated by using non-linear regression method. The estimated value of Michaelis kinetic constants for butanol (KmBt) and acid (KmAc) were 451.56 (M) and 4.7 × 10-7(M), respectively and the value of dissociation constant (KBt) of the butanol-lipase complex was 9.41 × 107(M). The estimated constants agreed fairly well with literature data.

Inhibition of the Human Ether-a-go-go-related Gene (HERG) K+ Channels by Lindera erythrocarpa

Lindera erythrocarpa Makino (Lauraceae) is used as a traditional medicine for analgesic, antidote, and antibacterial purposes and shows anti-tumor activity. We studied the effects of Lindera erythrocarpa on the human ether-a-go-go-related gene (HERG) channel, which appears of importance in favoring cancer progression in vivo and determining cardiac action potential duration. Application of MeOH extract of Lindera erythrocarpa showed a dose-dependent decrease in the amplitudes of the outward currents measured at the end of the pulse (I(HERG)) and the tail currents of HERG (I(tail)). When the BuOH fraction and H2O fraction of Lindera erythrocarpa were added to the perfusate, both I(HERG) and I(tail) were suppressed, while the hexane fraction, CHCl3 fraction, and EtOAc fraction did not inhibit either I(HERG) or I(tail). The potential required for half-maximal activation caused by EtOAc fraction, BuOH fraction, and H2O fraction shifted significantly. The BuOH fraction and H2O fraction (100 microgram/mL) decreased gmax by 59.6% and 52.9%, respectively. The H2O fraction- and BuOH fraction-induced blockades of I(tail) progressively decreased with increasing depolarization, showing the voltage-dependent block. Our findings suggest that Lindera erythrocarpa, a traditional medicine, blocks HERG channel, which could contribute to its anticancer and cardiac arrhythmogenic effect.

Sperm motility inhibiting activity of a phytosterol from Alstonia macrophylla Wall ex A. DC. leaf extract: a tribal medicine.

The role of methanolic extract and n-butanol fraction of A. macrophylla leaves was investigated on the forward motility of goat spermatozoa. The methanol extract (600 micro/g/ml) and one n-butanol fraction (Fraction A; 100 microg/ml) showed marked inhibition of sperm forward motility, tested by microscopic and spectrophotometric methods. Approximately, 50-60% of the spermatozoa lost their motility when treated with 600 microg/ml of methanol extract or 100 microg/ml of Fraction A. The Fraction A at 400 microg/ml concentration showed complete inhibition of sperm forward motility at 0 min. The inhibitory activity increased with the increasing concentrations of the fraction. The motility inhibitory activity of the Fraction A was stable to heat treatment at 100 degrees C for 2 min. The compound showed high inhibitory effect in the pH range 6.7-7.6. Fraction A also showed high efficacy for inhibiting human sperm motility, assessed by the microscopic method. The phytochemical analysis of methanolic extract of A. macrophylla leaves revealed the presence of sterols, triterpene, flavonoid, alkaloid, tannin and reducing sugar, while the Fraction A contains beta-sitosterol, a common phytosterol. The results demonstrate that Fraction A (beta-sitosterol) is a potent inhibitor of sperm motility and thus it has the potential to serve as a vaginal contraceptive.

Solvent effects on the rates of Aquitaine of bromopentamminecobalt [III] perchlorate in tert-butyl Alcohol-water media

The aquation kinetics of bromopentamminecobalt [III] ion has been investigated in tert-butyl alcohol-water mixtures, up to 75 percent by weight within the temperature range 40-60 degree. The variation of the thermodynamic parameters Delta G[*], Delta H[*] and Delta S[*] with the mole fraction of the organic solvent Was analyzed and is discussed. Moreover, a Delta H[*] - Delta S[*] plot is linear with a slope equal to 325 K which reveals the existence of a compensation effect due to a strong solute-solvent interaction. Finally the rate coefficients [k] are correlated with both the dielectric constant of the medium [D] and the concentration of water according to recently proposed equations

Studies on the effect of cholera substitution in the oxine molecule on the extraction of cadmium [II] into n-butanol

Extraction studies were undertaken with cadmium [II] in the presence of oxine and its chloro derivatives to derive information on the effect of substitution in the oxine molecule. Oxine, 5-chlorooxine and 5, 7-dichlorooxine form complexes with cadmium in the pH range7.9-8.4, 7 .8-8.2 and 7.0-7.6 respectively which was extract into n-butanol giving fairly intense yellow colour. The extracting species are found to be monomeric in cadmium in all the systems. pH dependence of log D plots revealed the release of two protons in the process of extraction. The optimum pH for extraction of cadmium chelates of 5-chlorooxine and 5, 7-dichlorooxine have drifted towards lower side when compared with that of cadmium. [Il]-oxine chelate. Bathochromic shifts were observed in the case of cadmium [II]-chlorooxine systems. The values of the conditional extraction constants suggest that the order of efficacy of extraction is as follows : Oxine < 5-chlorooxine < 5,7-dichlorooxine