Earticle

Inhibitory activity of active compound isolated from Ruta chalepensis leaf was examined against alcohol dehydrogenase and, upon comparison to those of four commercially available compounds (quinoline, quinoline-3-carboxaldehyde, quinoline-3-carboxylic acid, and quinoline-4-carboxylic acid) and 1,10-phenanthroline as alcohol dehydrogenase inhibitor, was characterized as quinoline-4-caboxaldehyde by spectral analyses. Inhibitory effects (IC50) of quinoline-4-caboxaldehyde and quinoline derivatives varied depending on chemicals and concentrations used. The IC50 values of quinoline-4-carboxaldehyde, quinoline-3-carboxaldehyde, quinoline, quinoline-3-carboxylic acid, and quinoline-4-carboxylic acid were 0.04, 0.3, 0.8, >1, and >1 mg/mL, respectively. These results suggest inhibitory action of quinoline-4-carboxaldehyde against alcohol dehydrogenase as prospective therapeutics for treatment of alcoholic liver diseases such as alcohol hepatitis and cirrhosis resulting from chronic alcohol abuse.

The insecticidal activities of active component isolated from Ruta chalepensis L. (Rutales: Rutaceae) leaves and its derivatives were examined using fumigant and contact toxicity methods against rice weevil, Sitophilus oryaze L. (Coleoptera: Curculionidae) adults. Administering the chloroform fraction of the methanol extract resulted in 87.7% mortality at $1.02mg/cm^2$ against S. oryzae adults, using a fumigant method. The insecticidal constituent of R. chalepensis leaves was isolated by chromatographic techniques, and identified as quinoline-4-carbaldehyde ($C_{10}H_7NO$). Based on the $LD_{50}$ values, the most toxic compound against S. oryzae was quinoline ($0.063mg/cm^2$), followed by quinoline-4-carbaldehyde ($0.084mg/cm^2$), and quinoline-3-carbaldehyde ($0.173mg/cm^2$) using the fumigant method. In the contact method, the most active compound against S. oryzae was quinoline ($0.057mg/cm^2$), followed by quinoline-4-carbaldehyde ($0.065mg/cm^2$), and quinoline-3-carbaldehyde ($0.092mg/cm^2$). Changing the position of aldehyde groups in the quinoline skeleton increases the insecticidal activities against S. oryzae. Furthermore, these results suggest that naturally occurring quinoline-4-carbaldehyde and its derivatives could have potential for managing populations of insect pests affecting stored food products.

This study was to isolate an active component of the chloroform fraction from the methanol extract of Ruta chalepensis leaves and to measure inhibitory effects against ${\alpha}$-glucosidase or ${\alpha}$-amylase. The inhibitory compound of R. chalepensis leaves was isolated using chromatographic methods and identified as quinoline. Quinoline and its structurally related derivatives were tested for their inhibitory activities by evaluating the $IC_{50}$ values against ${\alpha}$-amylase or ${\alpha}$-glucosidase and were compared with that of acarbose. Based on the $IC_{50}$ values, quinazoline exhibited the greatest inhibitory activity ($20.5{\mu}g/mL$), followed by acarbose ($66.5{\mu}g/mL$), and quinoline ($80.3{\mu}g/mL$) against ${\alpha}$-glucosidase. In case of ${\alpha}$-amylase, quinazoline had potent inhibitory activity, followed by quinoline ($179.5{\mu}g/mL$) and acarbose ($180.6{\mu}g/mL$). These results indicate that R. chalepensis extract, quinoline, and quinazoline could be useful for inhibiting ${\alpha}$-glucosidase or ${\alpha}$-amylase.

The growth responses of Ruta chalepensis leaf-derived materials toward human intestinal bacteria were examined. The biologically active constituent of the R. chalepensis extract was characterized as quinoline-4-carboxaldehyde($C_{10}H_{7}NO$). The growth responses varied depending on the bacterial strain, chemicals, and dose tested. At 0.25 and 0.1 mg/disk, quinoline-4-carboxaldehyde strongly inhibited the growth of Clostridium perfringens and weakly inhibited the growth of Escherichia coli without any adverse effects on the growth of three lactic acid bacteria. Furthermore, at 0.05 and 0.025 mg/disk, this isolate showed moderate activity against C. perfringens. In comparison, chloramphenicol at as low as 0.01 mg/disk significantly inhibited the growth of all bacteria tested, and cinnamaldehyde at 0.25 mg/disk did not inhibit Bifidobacterium bifidum, B. longum, E. coli, and Lactobacillus acidophilus, with the exception of C. perfringens. The structure-activity relationship revealed that quinoline-3-carboxaldehyde had strong growth inhibition against C. perfringens, but quinoline, quinoline-3-carboxylic acid, and quinoline-4-carboxylic acid did not inhibit the growth of B. bifidum, B. longum, C. perfringens, E. coli, and L. acidophilus. These results indicate that the carboxyl aldehyde functional group of quinolines seems to be required for growth-inhibiting activity against C. perfringens, thus indicating at least one of the pharmacological actions of R. chalepensis leaf.