In vitro inhibition of cytosolic carbonic anhydrases I and II by some new dihydroxycoumarin compounds

A new series of 6, 7-dihydroxy-3-(methylphenyl) chromenones, including three new derivatives, i.e. 6,7-dihydroxy-3-(2-methylphenyl)-2H-chromen-2-one (OPC); 6,7-dihydroxy-3-(3-methylphenyl)-2H-chromen-2-one (MPC); 6,7-dihydroxy-3-(4-methylphenyl)-2H-chromen-2-one (PPC) and one previously described, namely 6,7-dihydroxy-3-phenyl-2H-chromen-2-one (DPC), were synthesized. These compounds were investigated as inhibitors of human carbonic anhydrase I (hCA-I) and human carbonic anhydrase II (hCA-II) which had been purified from human erythrocytes on an affinity gel comprised of L-tyrosine-sulfonamide-Sepharose 4B.     

Design and synthesis of a series of serine derivatives as small molecule inhibitors of the SARS coronavirus 3CL protease

Synthesis of serine derivatives having the essential functional groups for the inhibitor of SARS 3CL protease and evaluation of their inhibitory activities using SARS 3CL R188I mutant protease are described. The lead compounds, functionalized serine derivatives, were designed based on the tetrapeptide aldehyde and Bai’s cinnamoly inhibitor, and additionally performed with simulation on GOLD softwear. Structure activity relationship studies of the candidate compounds were given reasonable inhibitors ent-3 and ent-7k against SARS 3CL R188I mutant protease. These inhibitors showed protease selectivity and no cytotoxicity.     

Enantioselective epoxidation of non-functionalized alkenes using carbohydrate based salen-Mn(III) complexes

Three new salen ligands with carbohydrate moieties were prepared from a salicylaldehyde derivative obtained by reaction of 1,2:5,6-di-O-isopropylidene-alpha-D-glucofuranose with 3-tert-butyl-5-(chloro-methyl)-2-hydroxybenzaldehyde. These ligands were coordinated with Mn(III) to give three chiral salen-Mn(III) complexes. The complexes were characterized and employed in the asymmetric epoxidation of unfunctionalized alkenes. Catalytic results showed that although there are no chiral groups on the diimine bridge, these complexes had some enantioselectivity, which indicates the carbohydrate moiety has an asymmetric inducing effect in the epoxidation reaction.     

Soil carbonate drives local adaptation in Arabidopsis thaliana

High soil carbonate limits crop performance especially in semiarid or arid climates. To understand how plants adapt to such soils, we explored natural variation in tolerance to soil carbonate in small local populations (demes) of Arabidopsis thaliana growing on soils differing in carbonate content. Reciprocal field‐based transplants on soils with elevated carbonate (+C) and without carbonate (?C) over several years revealed that demes native to (+C) soils showed higher fitness than those native to (?C) soils when both were grown together on carbonate‐rich soil. This supports the role of soil carbonate as a driving factor for local adaptation. Analyses of contrasting demes revealed key mechanisms associated with these fitness differences. Under controlled conditions, plants from the tolerant deme A1_(+C) native to (+C) soil were more resistant to both elevated carbonate and iron deficiency than plants from the sensitive T6_(?C) deme native to (?C) soil. Resistance of A1_(+C) to elevated carbonate was associated with higher root extrusion of both protons and coumarin‐type phenolics. Tolerant A1_(+C) also had better Ca‐exclusion than sensitive T6_(?C). We conclude that Arabidopsis demes are locally adapted in their native habitat to soils with moderately elevated carbonate. This adaptation is associated with both enhanced iron acquisition and calcium exclusion.     

Furanonaphthoquinones,atraric acid and a benzofuran from the stem barks of Newbouldia laevis

The series of naturally occurring furanonaphthoquinones is extended by identification of the derivatives 2-(1'-methylethenyl)-5-hydroxynaphtho[2,3-b]furan-4,9-dione and 2-(1'-methylethenyl)-7-hydroxynaphtho[2,3-b]furan-4,9-dione. They are accompanied in the stem barks of Newbouldia laevis by the known analogues 5-hydroxy-dehydro-iso-alpha-lapachone, 2-acetyl-5-hydroxynaphtho[2,3-b]furan-4,9-dione and 2-(1'-methylethenyl)naphtho[2,3-b]furan-4,9-dione along with the rare atraric acid and the new 2-(1'-methylethenyl)-6-hydroxy-2,3-dihydrobenzofuran. The structures of these compounds were established from spectroscopic studies.     

Antioxidant Properties of 2-O-β-D-Glucopyranosyl-L-ascorbic Acid

The antioxidant activity of a provitamin C agent, 2-O-β-D-glucopyranosyl-L-ascorbic acid (AA-2βG), was compared to that of 2-O-α-D-glucopyranosyl-L-ascorbic acid (AA-2G) and ascorbic acid (AA) using four in vitro methods, 1,1-diphenyl-picrylhydrazyl (DPPH) radical-scavenging assay, 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS^?+)-scavenging assay, oxygen radical absorbance capacity (ORAC) assay, and 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced erythrocyte hemolysis inhibition assay. AA-2βG slowly and continuously scavenged DPPH radicals and ABTS^?+ in roughly the same reaction profiles as AA-2G, whereas AA quenched these radicals immediately. In the ORAC assay and the hemolysis inhibition assay, AA-2βG showed similar overall activities to AA-2G and to AA, although the reactivity of AA-2βG against the peroxyl radical generated in both assays was lower than that of AA-2G and AA. These data indicate that AA-2βG had roughly the same radical-scavenging properties as AA-2G, and a comprehensive in vitro antioxidant activity of AA-2βG appeared to be comparable not only to that of AA-2G but also to that of AA.     

Chemotaxonomic Relationship Between Murraya and Merrillia (Rutaceae)

Swingle^[14-15] divided Aurantioideac into two tribes, one of which, Clausereae was further divided into three subtribes, namely, Micromelinae, Clauseninae and Merrilliinae. Mic romelinae and Merrilliinae each have one genus, whereas Clauseninae has three genera. Morphologically, the Clauseneae is a natural tribe, the five genera are related in a linear sequence, starting with Micromelum as the most primitive and progressing in sequence to Glycosmis, Clausena, Murraya and Merrillia. Chemical studies also support this linear relationship, as revealed by the degree of oxygenation and complexity of the 3-methyl carbazole alkaloids, from CH₃ and C1₃ in Glycosmis to CHO and C₁₈ in Clausena and COOH and C₂₃ in Murraya^[20-21]. Distribution of flavonoids also indicates the progression from Clauseninae to Merrilliinae^[18-19]. Extensive work has been conducted on the chemistry and taxonomy of the genus Murraya ^{[1,5,7-13,16]}, and the data from these studies clearly indicate the presence of two distinct groups. Based on a combination of morphological and chemical differences, we agreed with Tanaka^[16-17] in dividing Murraya into two sections, i.e. section Murraya and section Bergera^[1]. However, our previous study^[1] has not touched on the relationship between the two sections. Tanaka^[16-17] placed section Bergera before section Murraya, and indicated that the former is close to Micromelum and the latter to Merrillia. Swingle^[14-15], on the other hand, put taxa of section Murraya ahead of those of section Bergera, presumably suggesting that plants of section Murraya are more primitive than those of section Bergera, this arrangement was followed by Huang^[2-3]. The two conflicting viewpoints would have direct bearings on the interpretation of the trends of biogenesis of prenylated indole and carbazole alkaloids, as well as on the weighing of the relative advancement of the morphological characters within the genus, such as in the assignment of indices of divergence and in the construction of Wagner Divergence Diagrams. Without more objective criteria, we find it difficult to select one of the two systems. In order to determine the relationship between the two sections of Murraya, we decided to study plants of related genera, with the hope that the chemical data may shed light on the problem. A plant that attracted our attention is Merrillia caloxylon (Ridley) Swingle. So far, only eupatorin and a few other flavonoids have been reported from the fruit of this species^[4,6]. Although Me. caloxylon belongs to Merrilliinae, a subtribe next to Clauseninae, Tanaka^[16-17] believes that it is close to Murraya section Murraya. Swingle^[15], also suggested that this species might have developed from the same stock that gave rise to Mu. paniculata. If their interpretations were accurate, we would expect that Me. caloxylon would also contain yuehchukene and 8-prenylated coumarins. The presence of the antiimplantation agent would not only open up a new source of the compound but also help us judge the relationship between the two sections of Murraya. It is in this context that we studied the chemical composition of Me. caloxylon. Indeed, root and stem bark of Me. caloxylon were found to contain the antiimplantation indole alkaloid yuehchukene (1), and the 8-prenylated coumarins sibiricin (II) and phebalosin (III), as well as 3-(3-methy1-buta-1,3-diene) indole (IV) and eupatorin (V.) Details on the chemical profiles are reported in another paper. Through this exercise, we have confirmed the close relationship between Merrilliinae and Murraya section Murraya, plants of both taxa contain yuehchukene and 8-prenylated coumarins, but no carbazole alkaloid. Root and stem bark of Me. caloxylon, like those of plants of section Murraya, are strawcolored to pale whitish. Its leaves also bear wings along the rachis an in Mu. alata, and the seeds are also villous. However, Me. caloxylon has long trumpetshaped flowers 55-60 mm long, much larger than those found in other rutaceous plants. Its fruit is ob long, up to 11 cm long and 8 cm across, bearing a thick and warty pericarp, exuding a very stick mucilage when cut, and containing numerous seeds (>30). The plant was known to exist in the Malay Peninsula and north Sumatra^[15], but, according to David Jones (per. comm.) of the University of Malaya, is now only available in cultivation in Malaysia and Singapore, a limitation to any further exploitation as an additional source of yuehchukene. Besides confirming the close relationship between Merrillia and section Murraya, we may also conclude that section Bergera is close to Glycosmis and Clausena, since they are known to contain carbazole alkaloids but no yuehchukene. Accordingly, we find Tanaka’s arrangement more acceptable: plants of section Bergera are more primitive than those of section Murraya, the former is close to Clausena whereas the latter (notably Mu. alata) to Merrillia. The relationship among the gonera with in Clauseneae may be illustrated as follow: Micromelum→ Glycosmis→Clausena→Murraya sect. Bergera→Murraya sect. Murraya→Marrillia. Accordingly, we may decide that the following character states are more primitive among plants of Murraya and Merrillia: root and stem bark dark brown, leaf rachis wingless, flower small, fruit purple-black with few seeds, and seed coat glabrous. In contrast, strawcolored or pale whitish bark, winged leaf rachis, large flower, red or yellow fruit with many seeds and villous seed coat can be regarded as more advanced characters. Acknowledgments Partial support was received from the World Health Organization Special Programme on Human Reproduction and the Kevin Hsu Research Fund (to YCK) and Commonwealth Science Council (to PPHB). The staff of the Singapore Botanic Gardens and the Forest Research Institute of Malaysia are thanked for their assistance in collecting plantmaterial.     

Perylenequinones from Curvularia lunata

Three perylenequinones, the methylated 12-epi-stemphytriol (1), dihydroalterperylenol (2), and alterperylenol (3), were isolated from cultures of Curvularia lunata (LBQM-04) on malt extract broth. All these compounds were obtained from this particular fungus for the first time. Structures of compounds were determined based on MS and NMR spectra, as well as by comparison with the literature reports. The isolation of these phytotoxic reduced perylenequinones from the Curvularia genus suggested that they may occur in any anamorphic fungi belonging to the Pleosporaceae family.     

Enhanced efficiency due to the use of achiral additives in the optical resolution of 1-phenylethylamine by its glutaric acid derivative

Racemic 1-phenylethylamine was optically resolved by its own derivative formed with glutaric acid namely (+)-(R)-N-(1-phenylethyl)glutaramic acid. The amide acid resolving agent was synthesized from (+)-(R)-1-phenylethylamine by N-derivatization. The glutaric acid derivative was the next in a homologous series of dicarboxilic acid derivatized resolving agents of racemic 1-phenylethylamine. Resolution results obtained with the oxalic, malonic, and succinic acid derivatives were previously discussed(1). Each of the above derivative resolving agents could be successfully applied as resolving agents of 1-phenylethylamine. The efficiency of the present optical resolution using (+)-(R)-N-(1-phenylethyl)glutaramic acid resolving agent was remarkably inferior to the results obtained by its shorter chained homologues(1). Use of achiral additives, like urea, thiourea, N-methylurea, and N,N'-dimethylurea caused large increase in the efficiency of the resolution by (+)-(R)-N-(1-phenylethyl)glutaramic acid resolving agent. Precipitated salts obtained in the resolutions performed in the presence of the additives were investigated by thermoanalysis, X-ray powder diffraction, and optical microscopy. Based on the analytical data, the improvement of the resolution results was attributed to the influence of the additives on the crystal nucleation processes of the diasteromeric salts.     

Simultaneous analysis of three bioactive compounds in Artemisia annua hairy root cultures by reversed-phase high-performance liquid chromatography-diode array detector

Introduction – Artemisia annua is a rich source of biologically active substances such as terpenoids, coumarins and polyacetylenes. These chemicals have been reported to show beneficial pharmacological properties such as antitumor and antibacterial activities. In genetically transformed root cultures of A. annua, three bioactive metabolites, namely, ponticaepoxide (an insecticidal polyacetylene, 1 ), drimartol A (an anticancer sesquiterpene coumarin, 2 ) and (Z)‐7‐acetoxy‐methyl‐11‐methyl‐3‐methylene‐dodeca‐1,6,10‐triene (a new anticancer sesquiterpene, 3 ) were isolated and identified in our recent work. However, no quantitative analysis methods for any of them are yet available, nor for their simultaneous analysis. Objective – To develop an HPLC‐PAD method for simultaneous determination of 1 , 2 and 3 in hairy root cultures of A. annua. Methodology – HPLC operating conditions were optimised and the chromatographic separation was performed on a C₁₈ column with a gradient acetonitrile : water as mobile phase. Results – Linear relationships within the range of investigated concentrations were observed for the three metabolites with their correlation coefficients greater than 0.997. The method was validated for repeatability (RSD <3.59%) and intra‐ and inter‐day precision (RSD <3.1%) with recovery between 94.8 and 107.6% and the RSD less than 3.40%. The method was successfully applied to the time‐course of accumulation of the bioactive compounds in genetically transformed root cultures of A. annua. Conclusion – The HPLC‐PAD method developed for the simultaneous determination of three bioactive metabolites 1 , 2 and 3 was simple, reproducible and sensitive. Copyright © 2010 John Wiley & Sons, Ltd.