Esters from Ferula samarcandica
In continuation of research on terpenoid plants of the Ferula L. genus (Apiaceae), we studied components of the roots of Samarkand ferula ( Ferula samarcandica Korov.) collected in Tashkent district. The terpenoid coumarins samarcandin and samarcandone were isolated previously from Samarkand ferula [1]. Later, a study of Samarkand ferula misidentified as mogoltav ferula ( F. mogoltavica Lipsky ex Korov.) isolated the terpenoid coumarins samarcandin, samarcandone, mogoltadone, gummosin, and farnesiferol A [2-4]. Air-dried ground roots were extracted with ethanol. The alcohol extract was evaporated, diluted with water (1:2), and treated with ethylacetate. The combined ethylacetate extract was distilled to produce a thick extract that was placed on a col umn of KSK silica gel (d = 3 cm, h = 80 cm) and eluted by benzine:ethylacetate (9:1) with a subsequent increase of ethylace tate concentration. Fractions of 100 mL were collected. The separation of the total terpenoids was monitored using TLC (hydrocarbons:ethylacetate, 4:1; developer, 1% vanillin in conc. H 2SO4). Four terpenoid esters were isolated: 1, C17H22O3, mp 155-156°C; 2, C18H24O4, mp 84-85°C; 3, C18H24O4, [α]D 22 -30 (c 0.5, ethanol); 4, C22H28O5, mp 129-130°C. Comparison of the PMR, UV, IR, and mass spectra of 1 and 2 with those in the literature identified them as tschimgin and tschimganin [5]. The IR spectrum (KBr, ν, cm) of 3 exhibited absorption bands typical of hydroxyl (3534), ester carbonyl (1693), and an aromatic ring (1598, 1514) [6]. The mass spectrum of 3 was similar to that of esters of monoterpene alcohols and had peaks for ions with m/z 304 [M]+, 168 (C8H8O4), 148, 123, 95, 93. The PMR spectrum (100 MHz, DMSO-d 6, δ, ppm, J/Hz) of 3 exhibited signals at 0.70, 0.80, and 1.02 (each 3H, s), 3.65 (3H, s, OCH 3), 7.10 (1H, d, J = 9.0, H-3 ′), 7.72 (1H, d, J = 2, H-6 ′), 7.75 (1H, q, J 1 = 9.0, J2 = 2, H-2′), 4.90 (1H, d, J1 = J2 = 7.5) and 5.15 (1H, br.d, J = 10). The two signals at 4.90 and 5.15 ppm in the range of geminal protons indicate that 3 is a natural mixture of tschimganin and iso-tschimganin. Similar mixtures of tschimgin/ iso-tschimgin and tschimganin/ isotschimganin were isolated from F. dshizakensis Korov. and F. angreni Korov. [7, 8]. The neutral part of the hydrolysate from base hydrolysis of 3 by aqueous KOH (5%) afforded a monoterpene alcohol of composition C10H18O with mp 201-202 °C that was identified as borneol [5]. Comparison of the PMR, IR, and mass spectra of 4 with those of known carotane esters showed that this compound was lancerodiol p-hydroxybenzoate, which was isolated earlier from F. lancerottensis [9]. Thus, it is found for the first time that Samarkand ferula contains esters of terpenoid alcohols in addition to terpenoid coumarins.
Carotane sesquiterpenes from Ferula lancerottensis
Abstract Six new carotane sesquiterpenes, the p -hydroxybenzoate of epoxyjaeschkeanadiol the p -methoxybenzoate and p -hydroxybenzoate of lancerodiol, lancerodiol, the p -hydroxybenzoate of lancerotriol and the p -methoxybenzoate of linkitriol, and the already known p -hydroxybenzoate of jaeschkeanadiol have been isolated from Ferula lancerottensis .
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.