Two new components from the roots of Angelicae koreana Kitagawa
Two new compounds, 2-hydroxyethylcarboxylic acid-5,9-eicodien-carboxylate and 1-(2′-propenoxy)undec-2-ene, and two known compounds, 2-hydroxy-4-methyl-acetophenone and β-sitosterol, were isolated from the roots of Angelicae koreana Kitagawa. The structures of the compounds were established on the basis of MS and NMR spectral data.
Identification and antifungal activity of novel organic compounds found in cuticular and internal lipids of medically important flies.
Novel organic compounds found in the cuticular and internal lipids of medically important flies were identified. Uracil, 9-tricosene, 1-oleoyl glycerol, dimethyl suberate and butyl stearate were tested for their potential antifungal activity. Minimal inhibitory concentrations of the compounds against reference strains of fungi were determined. Uracil and dimethyl suberate slightly inhibited the growth of entomopathogenic fungi. The cuticular and internal lipids of Calliphora vicina, Calliphora vomitoria, Sarcophaga carnaria and Musca domestica were studied by gas chromatography (GC) combined with mass spectrometry (GC/MS). A comparison of the lipid extracts between the preimaginal and mature stages showed adults flies contained a higher total content of the identified components. Furthermore, their amounts distinctly predominated in the internal lipids of all the species. The amount of 9-tricosene was the highest in adults of C. vicina, while the larvae and pupae had a definitively lower amount of this compound. Uracil was found to be the most abundant component in extracts obtained from C. vomitoria especially in the internal lipids of adults. 1-oleoyl glycerol was detected in all of the examined species of flies. It was most abundant in the internal extracts isolated from the larvae of C. vicina and the pupae of C. vomitoria. Suberic acid dimethyl ester was found in the larval and pupal internal lipids of C. vicina and S. carnaria in low amounts. Butyl stearate was identified only in the internal lipids of the larvae and adults of houseflies.
New method for analysis of enzymatic reactions: Thermolysin-catalyzed synthesis of aspartame precursor
Aspartame is an artificial sweetener which is 200 times sweeter than sucrose. A precursor of aspartame, N-(benzyloxycarbonyl)-l-aspartyl-l-phenylalanine methyl ester (Z-APM) was synthesized and hydrolyzed with thermolysin in an aqueous monophasic system. Graphical plotting methods and/or nonlinear regression have been used to analyze enzymatic reactions because of the nonlinearity of enzymatic rate equations. There are, however, problems: the former require accurate measurement of the initial reaction rate and the latter gives no analytical information. The authors proposed a method to solve the nonlinear enzymatic rate equations with respect to the concentration of a product with the Taylor expansion, especially for the reversible Theorell-Chance mechanism (Murakami, Y., Hirata, M., and Hirata, A., J. Ferment. Bioeng., 82, 246–252, 1996). This solution, however, is complex for practical use. In this paper, a simpler solution to explain the thermolysin-catalyzed synthesis of Z-APM is obtained. New methods to determine the kinetic parameters, especially for the reversible Theorell-Chance mechanism, based on the approximated solution are proposed. The results calculated using the obtained kinetic parameters can satisfactorily explain the experimental results, which demonstrates the effectiveness of the proposed analysis. We must know the relation between the concentrations of substrates and a product, and accurately evaluate of the result obtained using Taylor expansion when we determine the kinetic parameters using our newly developed methods. The methods to determine the kinetic parameters of the reversible Theorell-Chance mechanism described in this paper is, however, expected to be applied to general enzymatic reactions.