Spectrophotometric determination of acid dissociation constants of some arylpropionic acids and arylacetic acids in acetonitrile-water binary mixtures at 25ºC

Abstract The acid dissociation constant of drug active compounds (arylpropionic and aryl acetic acids) were determined in acetonitrile and water binary mixtures (corresponding volume fractions of 0.40, 0.45, 0.50, and 0.55) by using a multi-wavelength spectrophotometric method. Drug active compounds, which were slightly soluble in water, were studied in these binary mixtures. The dissociation constants of drug active compounds are important in drug design studies and in any research of the biopharmaceutical and physicochemical properties of drugs. The STAR program was used for the determination of dissociation constants. The acidity constants of arylpropionic and aryl acetic acids were correlated with the Kamlet and Taft solvaatochromic parameters. Aqueous pKa values of these arylpropionic and aryl acetic acids were determined from pKa values obtained from acetonitrile and water binary mixtures with varying volume fractions. The studied drugs had a pKa value corresponding to base functional group. Results showed that the acid dissociation constant values of the drug active compounds increased with an increase in acetonitrile content in the medium.

Analgesic and antioxidant activities of the methanolic extract of Operculina turpethum leaves in mice.

Background: Operculina turpethum Linn. (Convolvulaceae) is commonly called “Trivrit” or “India jalap” in English. It is a perennial herbaceous plant with purplish stem and milky-white exudates. This study was aimed at evaluation of the analgesic and antioxidant effects of the methanolic extract of O. turpethum leaves in mice. Methods: The acute oral toxicity of the extract was evaluated using up and down method. The analgesic effects were assessed using acetic acid-induced abdominal writhing reflex and tail flick methods, while the antioxidant activity (AA) was assayed using photometric 2, 2-diphenyl-1-picrylhydrazyl free radical scavenging assay method. Results: The extract produced a concentration-dependent increase in the AA with inhibitory concentration 50% >400 μg/ml. The extract (100, 200 and 400 mg/kg) and aspirin (100 mg/kg) produced a significant (p<0.05) dose-dependent reduction in the number of abdominal constriction induced by intraperitoneal injection of acetic acid in treated mice when compared to the distilled water treated mice. The extract (100, 200, and 400 mg/kg) and pentazocine (3 mg/kg) caused a significant (p<0.05) dose-dependent increase in the pain reaction time in the treated mice groups, when compared to the distilled water treated groups. Conclusion: The study showed that O. turpethum possesses analgesic and antioxidant properties and confirmed the folkloric use of O. turpethum leaves in the traditional pain management.

Molecular characterisation and biomass and metabolite production of Lactobacillus reuteri LPB P01-001: a potential probiotic

Lactobacillus reuteri LPB P01-001 was isolated from the gastrointestinal tract of wild swine and was characterised by biochemical testing and sequencing of gene 16S rRNA. A simple and low-cost culture medium based on cane sugar (2.5% p/v) and yeast extract (1% p/v) was used in the production of this probiotic. The fermentative conditions were a) pH control at 6.5 and b) no pH control; both were set at 37°C in a 12 L slightly stirred tank bioreactor. Fermentation parameters such as the specific growth rate, productivity and yield of biomass, lactic and acetic acid levels were determined. L. reuteri LPB P01-001 behaves as an aciduric bacteria because it grows better in a low pH medium without pH control. However, the lactic acid production yield was practically half (9.22 g.L-1) of that obtained under a constant pH of 6.5, which reached 30.5 g.L-1 after 28 hours of fermentation. The acetic acid production was also higher under pH-controlled fermentation, reaching 10.09 g.L-1 after 28 hours of fermentation. These parameters may raise the interest of those committed to the efficient production of a probiotic agent for swine.