We herein report our studies into the effects of microwave irradiation on the solvent-free esterification of L-leucine with alcohols. In the absence of solvent, microwave irradiation accelerated the reaction compared ...We herein report our studies into the effects of microwave irradiation on the solvent-free esterification of L-leucine with alcohols. In the absence of solvent, microwave irradiation accelerated the reaction compared to conventional oil bath heating. Measurement of the dielectric properties under the reaction conditions revealed that the high dielectric loss factor of the reaction mixture containing L-leucine, n-butanol, and a p-toluene sulfonic acid catalyst could be attributed to the acceleration of the reaction. The depth of microwave penetration into the reaction mixture as derived from the in-situ measurement of the dielectric properties was ~13 mm, which suggested that a thinner reaction vessel was favorable for the esterification of L-leucine. In addition to the batch reaction using a desktop microwave reactor, two types of flow reaction were also performed using a desktop tubular reactor and a semi-bench-scale tubular reactor. These flow reactions also exhibited high performances, thus allowing the scale-up of this reaction system for industrial use.展开更多
Objective:To investigate the effect of alpha-lipoic acid(ALA)supplementation on systolic blood pressure(SBP),renal oxidant-antioxidant status and renal damage in spontaneously hypertensive rats(SHR)and SHR administere...Objective:To investigate the effect of alpha-lipoic acid(ALA)supplementation on systolic blood pressure(SBP),renal oxidant-antioxidant status and renal damage in spontaneously hypertensive rats(SHR)and SHR administered with Nω-nitro-L-arginine methyl ester(L-NAME).Methods:Male rats were divided into four groups(SHR,SHR+ALA,SHR+L-NAME,SHR+ALA+L-NAME).The respective group of rats was administered with ALA(100 mg/kg/day)from age 4 weeks to 28 weeks and L-NAME(25 mg/kg/day)from age 16 weeks to 28 weeks.SBP was measured every two weeks and twenty four hour urine was collected at 4 weeks,16 weeks and 28 weeks for estimation of protein,creatinine and N-acetyl-e end of 28 weeks,rats were sacrificed and blood and kidneys colα-Dglucosaminidase.At thlected for assessment of blood creatinine,kidney thiobarbituric acid reactive substances,protein carbonyls,superoxide dismutase,catalase,glutathione peroxidase,glutathione reductase,glutathione S-transferase,glutathione disulfide,glutathione,total antioxidant status and nitric oxide as well as histopathological examination.Results:ALA supplementation significantly reduced SBP of SHR and SHR+L-NAME rats when compared to their respective non-supplemented groups.Renal oxidant status markers including thiobarbituric acid reactive substances and protein carbonyls were significantly reduced on SHR and SHR+L-NAME rats supplemented with ALA at 28 weeks as well as ALA supplementation significantly increased renal antioxidants including superoxide dismutase,catalase,glutathione peroxidase,glutathione S-transferase,glutathione and glutathione/glutathione disulfide ratio at 28 weeks.No significant change in nitric oxide levels was observed between the ALA supplemented and non-supplemented groups.Renal dysfunction was ameliorated on ALA supplementation as evidenced by significant reduction in urine protein levels,N-acetyl-α-D-glucosaminidase activity and significant increase of creatinine clearance in SHR and SHR+L-NAME at 28 weeks.Renal histopathological examination showed that ALA supplementation prevented vascular damage in SHR and ameliorated glomerular damage in SHR+L-NAME at 28 weeks.Conclusions:ALA has hypotensive and renoprotective effects on both SHR and SHR+LNAME,which could be due to its ability to ameliorate oxidative stress in the kidneys.展开更多
Distribution behavior of mandelic acid enantiomers was examined in a two-phase aqueous-organic solvent mixture containing L-tartaric esters. The influences of pH, length of alkyl chain of L-tartraic esters, organic so...Distribution behavior of mandelic acid enantiomers was examined in a two-phase aqueous-organic solvent mixture containing L-tartaric esters. The influences of pH, length of alkyl chain of L-tartraic esters, organic solvents and concentrations of phosphate salt on partition coefficient(K) and separation factor(α) were investigated. The results show that L-tartaric esters studied all form more stable diastereomeric complexes with D-enantiomer than with L-enantiomer. With rise of pH, K decrease, but α increase. With addition of length of alkyl chain of L-tartaric esters, K and α decrease. Organic solvents and concentrations of phosphate salt also show a great influence on K and α. K L, K D and α are 2.523, 2.674 and 1.06, respectively, when mandelic acid enantiomers were extracted by di-O-pentyl-L-tartaric ester in n-decanol at pH=2.3.展开更多
文摘We herein report our studies into the effects of microwave irradiation on the solvent-free esterification of L-leucine with alcohols. In the absence of solvent, microwave irradiation accelerated the reaction compared to conventional oil bath heating. Measurement of the dielectric properties under the reaction conditions revealed that the high dielectric loss factor of the reaction mixture containing L-leucine, n-butanol, and a p-toluene sulfonic acid catalyst could be attributed to the acceleration of the reaction. The depth of microwave penetration into the reaction mixture as derived from the in-situ measurement of the dielectric properties was ~13 mm, which suggested that a thinner reaction vessel was favorable for the esterification of L-leucine. In addition to the batch reaction using a desktop microwave reactor, two types of flow reaction were also performed using a desktop tubular reactor and a semi-bench-scale tubular reactor. These flow reactions also exhibited high performances, thus allowing the scale-up of this reaction system for industrial use.
基金supported by Short Term Research Grant Scheme(304/PPSP/6131496)provided by Universiti Sains Malaysia.
文摘Objective:To investigate the effect of alpha-lipoic acid(ALA)supplementation on systolic blood pressure(SBP),renal oxidant-antioxidant status and renal damage in spontaneously hypertensive rats(SHR)and SHR administered with Nω-nitro-L-arginine methyl ester(L-NAME).Methods:Male rats were divided into four groups(SHR,SHR+ALA,SHR+L-NAME,SHR+ALA+L-NAME).The respective group of rats was administered with ALA(100 mg/kg/day)from age 4 weeks to 28 weeks and L-NAME(25 mg/kg/day)from age 16 weeks to 28 weeks.SBP was measured every two weeks and twenty four hour urine was collected at 4 weeks,16 weeks and 28 weeks for estimation of protein,creatinine and N-acetyl-e end of 28 weeks,rats were sacrificed and blood and kidneys colα-Dglucosaminidase.At thlected for assessment of blood creatinine,kidney thiobarbituric acid reactive substances,protein carbonyls,superoxide dismutase,catalase,glutathione peroxidase,glutathione reductase,glutathione S-transferase,glutathione disulfide,glutathione,total antioxidant status and nitric oxide as well as histopathological examination.Results:ALA supplementation significantly reduced SBP of SHR and SHR+L-NAME rats when compared to their respective non-supplemented groups.Renal oxidant status markers including thiobarbituric acid reactive substances and protein carbonyls were significantly reduced on SHR and SHR+L-NAME rats supplemented with ALA at 28 weeks as well as ALA supplementation significantly increased renal antioxidants including superoxide dismutase,catalase,glutathione peroxidase,glutathione S-transferase,glutathione and glutathione/glutathione disulfide ratio at 28 weeks.No significant change in nitric oxide levels was observed between the ALA supplemented and non-supplemented groups.Renal dysfunction was ameliorated on ALA supplementation as evidenced by significant reduction in urine protein levels,N-acetyl-α-D-glucosaminidase activity and significant increase of creatinine clearance in SHR and SHR+L-NAME at 28 weeks.Renal histopathological examination showed that ALA supplementation prevented vascular damage in SHR and ameliorated glomerular damage in SHR+L-NAME at 28 weeks.Conclusions:ALA has hypotensive and renoprotective effects on both SHR and SHR+LNAME,which could be due to its ability to ameliorate oxidative stress in the kidneys.
文摘Distribution behavior of mandelic acid enantiomers was examined in a two-phase aqueous-organic solvent mixture containing L-tartaric esters. The influences of pH, length of alkyl chain of L-tartraic esters, organic solvents and concentrations of phosphate salt on partition coefficient(K) and separation factor(α) were investigated. The results show that L-tartaric esters studied all form more stable diastereomeric complexes with D-enantiomer than with L-enantiomer. With rise of pH, K decrease, but α increase. With addition of length of alkyl chain of L-tartaric esters, K and α decrease. Organic solvents and concentrations of phosphate salt also show a great influence on K and α. K L, K D and α are 2.523, 2.674 and 1.06, respectively, when mandelic acid enantiomers were extracted by di-O-pentyl-L-tartaric ester in n-decanol at pH=2.3.
