Calorimetric determination of thermodynamic parameters of 2′-dUMP binding to Leishmania major dUTPase

We have investigated the binding of 2′-deoxyuridine 5′-monophosphate (2′-dUMP) to Leishmania major deoxyuridine 5′-triphosphate nucleotide hydrolase (dUTPase) by isothermal titration microcalorimetry under different experimental conditions. Binding to dimeric L. major dUTPase is a non-cooperative process, with a stoichiometry of 1 molecule of 2′-dUMP per subunit. The utilization of buffers with different ionization enthalpies has allowed us to conclude that the formation of the 2′-dUMP–dUTPase complex, at pH 7.5 and 30 °C, is accompanied by the uptake of 0.33±0.05 protons per dUTPase subunit from the buffer media. Moreover, 2′-dUMP shows a moderate affinity for the enzyme, and binding is enthalpically driven across the temperature range studied. Besides, whereas ΔG° remains practically invariant as a function of temperature, both ΔH and ΔS° decrease with increasing temperature. The T_S and T_H were 23.4 and 13.6 °C, respectively. The temperature dependence of the enthalpy change yields a heat capacity change of ΔC_p°=?618.1±126.4 cal·mol^?1·K^?1, a value low enough to discard major conformational changes, in agreement with the fitting model. An interpretation of this value in terms of solvent-accessible surface areas is provided.     

Luteolin 7-glucuronide-3′-mono(trans)ferulylglucoside and other unusual flavonoids in the aquatic liverwort complex, Riccia fluitans

Thirteen flavonoid glycosides, including eight which are new have been identified in Riccia fluitans; aquatic and terrestrial forms of this plant have the same pattern. Luteolin 7-O-glucuronide-3′-O-mono(trans)ferulylglucoside is proposed as the type flavonoid for this species. Its absence from, and the presence of chrysoeriol in R. duplex, support the proposed separation of R. duplex from the R. fluitans complex. A micro-deacylation technique is described which can also be used for specific deglycosylation of luteolin glycosides at the 4′-hydroxyl.     

Flavonoids of Gardenia cramerii and G. fosbergii bud exudates

From the bud exudates of Gardenia cramerii and G. fosbergii, two species endemic to Sri Lanka, a new flavonoid with an unusual B-ring oxidation pattern, 5,5′-dihydroxy-6,7,2′,3′-tetramethoxyflavone, was characterized. Two other rare flavonoids, 5,3′,5′-trihydroxy-3,6,7,4′-tetramethoxyflavone and 5-hydroxy-6,7,3′,4′,5′-pentamethoxyflavone were also isolated from both Gardenia species.     

Effect of substituents at phenyl group of 7,7′-dioxo-9,9′-epoxylignane on antifungal activity

Using 21 newly synthesized 7,7′-dioxo-9,9′-epoxylignane derivatives having a modified 7-phenyl group, we examined the relationship between their structure and antifungal activity against plant pathogens such as Bipolaris oryzae to determine the effects of various substituents on the antifungal activity. Compared with the lead compound having a 4-OH-3-CH₃O-phenyl moiety, several analogs showed higher antifungal activity against B. oryzae, including the compound having an unsubstituted phenyl group and those having either of the following phenyl substituents: 2-OH, 4-CH₃O, 4-C₂H₅O, 4-n-C₃H₇O, 4-n-C₄H₉O, 4-CF₃O, 4-C₂H₅, or 4-Cl. On the other hand, the activity of compounds having a branched substituent, such as 4-i-C₃H₇O or 4-i-C₃H₇, on the 7-phenyl group or a multi-substituted phenyl group was equipotent or inferior to that of the lead compound. These results as well as correlations between the antifungal activity of the test compounds and the physicochemical parameters of the varied substituents suggest that the position of substitution on the 7-phenyl group and the incorporation of substituents with optimal physicochemical properties are important for exerting the antifungal activity.     

Occurrence of a 3′-phosphoadenosine 5′-Phosphosulphate synthesizing system In two Ochromonas species

The presence of an enzyme capable of incorporating ³⁵SO₄^2? into 3′-phosphoadenosine 5′-phosphosulphate has been demonstrated,in Ochromonas danica and O. malhamensis. This system probably includes the enzymes ATP:sulphate adenyltransferase. E.C. 2.7.7.4 and ATP:adenylsulphate 3′-phosphotransferase, E.C. 2.7.1.25.     

Two isomeric flavanones from vitex negundo

Two new flavanoids, characterized as 5,3′-dihydroxy-7,8,4′-trimethoxyflavanone and 5,3′-dihydroxy-6,7,4′-trimethoxyflavanone, have been isolated from the leaves of Vitex negundo.     

Algal carotenoids with novel end groups

The structures of three previously unidentified carotenoids from Eutreptiella gymnastica are reported. These include siphonein with defined n-2-trans-2-dodecenoic esterifying acid and assigned 3R(?), 3′R,6′R chirality, (3R)-3′,4′-anhydrodiatoxanthin and eutreptiellanone (3,6-epoxy-3′,4′,7′,8′-tetradehydro-5,6-dihydro-β,β-caroten-4-one) with probable 3S,5R,6S chirality.     

Thiolytic cleavage of the anti-tumour compound 4′-(9-acridinylamino)-methanesulphon-m-anisidine (m-AMSA,NSC 156 303) in blood

4′-(9-acridinylamino)methanesulphon-m-anisidide (m-AMSA), a compound with a broad spectrum of experimental anti-tumour activity, was found to have a short biological half-life in mice bearing L1210 leukaemia. The fate of m-AMSA [³H]-labelled in the acridine nucleus, was determined following injection into mice. There was rapid formation of covalent adducts with plasma proteins. Adducts were also formed in freshly isolated blood samples following incubation at 37°C, and were found to be highly fluorescent. The formation of adducts was accompanied by a decrease in the free thiol concentration in plasma, and the concomitant addition of radioactivity from [³H]acridine nuclei. Acid or alkaline hydrolysis of the plasma protein adduct liberated acridone, while digestion with a protease produced unstable fluorescent compounds. A comparison of the rates of acid hydrolysis of the adducts and of model compounds suggested that the adducts were produced as a result of nucleophilic attack at the C-9 position of m-AMSA by protein thiol groups. The side chain of m-AMSA was liberated as 4-amino-3-methoxymethanesulphonanilide. Several congeners of m-AMSA were shown to form similar or identical adducts both in vivo and in vitro, and at rates which correlated with their reactivity towards simple organic thiols.     

Inhibitory effect of 8-substituted adenosine derivatives on Ca++ and modulator protein-dependent phosphodiesterase activity.

8-Substituted adenosine and cyclic AMP derivatives exhibited some negative Cotton effects in circular Dichroism at B_2u band in pH 7.5 solution, suggesting that these derivatives take syn conformation. The adenosine derivatives, as well as cyclic AMP derivatives, competitively inhibited the cyclic AMP hydrolyzing activity in Ca⁺⁺ and modulator protein-dependent phosphodiesterase preparation from hog brain cortex. The inhibitory potential of an adenosine derivative was lower than that of the cyclic AMP derivative having the same substituent by the lack of the phosphate moiety for which affinity was 0.5 kcal / mol. These results may suggest that the cyclic AMP hydrolyzing site on the enzyme requires the syn conformation of purine riboside.     

Flavones from Eupatorium leucolepis

Chloroform extraction of Eupatorium leucolepis gave the new flavones 3′-hydroxy-5,6,7,8,4′,5′-hexamethoxyflavone, 4′-hydroxy-5,6,7,8,3′,5     

Three methylated flavones from Thymus vulgaris

Three highly oxygenated flavones were isolated from leaves of Thymus vulgaris. Their structures were determined by spectroscopic methods as 5, 6, 4′-trihydroxy- 7, 8, 3′-trimethoxyflavone (thymonin), 5, 4′-dihydroxy-6, 7, 3′-trimethoxyflavone (cirsilineol) and 5, 4′-dihydroxy-6, 7, 8, 3′-tetramethoxyflavone. These flavones are reported for the first time in the genus Thymus.     

Two new flavone glycosides from Cirsium lineare

An examination of four species of Cirsium disclosed the presence of two new flavonoids in C. lineare. The structure of one was 5,4′-dihydroxy-6,7,3′-trimethoxyflavone (cirsilineol) 4′-monoglucoside and the other 5,3′,4′-trihydroxy-6,7-dimethoxyflavone (cirsiliol) 4′-monoglucoside. Luteolin 7-glucoside was found in C. suffultum, and pectolinarin and linarin in C. kamtschaticum and C. pectinellum.     

Chirality of plectaniaxanthin

The chirality of plectaniaxanthin, a carotenoid vic. glycol from Plectania coccinea, could not be determined by the modified Horeau method. Chiroptical correlation of plectaniaxanthin acetonide and (2′S)-16′, 17′-dinorplectaniaxanthin acetonide was taken as proof of 2′R chirality for natural plectaniaxanthin and its mono- and diesters. The synthesis of the chiral model carotenoid was effected from d-mannitol via 2, 3-O-isopropylidene-d-glyceraldehyde as key synthon.     

Two new C-methylated flavonoids from Myrica gale

From the leaves of Myrica gale 2′,4′-dihydroxy-6′-methoxy-3′,5′-dimethylchalcone has been isolated. The fruits yielded 2′-hydroxy-4′,6′-dimethoxy-3′-methyldihydrochalcone. The constitutions were deduced from spectroscopic data and confirmed by synthesis.     

Preparation of 5′-deoxy-5′-amino-5′-C-methyl adenosine derivatives and their activity against DOT1L

From a readily available 5-C-Me ribofuranoside, we have realized a reliable route to valuable 5′-deoxy-5′-amino-5′-C-methyl adenosine derivatives at gram scale with confirmed stereochemistry. These adenosine derivatives are useful starting materials for the preparation of 5′-deoxy-5′-amino-5′-C-methyl adenosine derivatives with higher complexity. From one of the new adenosine derivatives, some 5′-deoxy-5′-amino-5′-C-methyl adenosine DOT1L inhibitors were prepared in several steps. Data from DOT1L assay indicated that additional 5′-C-Me group improved the enzyme inhibitory activity.     

5′-Monohydroxyphylloquinone from Anacystis and Euglena

The monohydroxy analogue of phylloquinone found in Anacystis nidulans and Euglena gracilis has been characterized as 5′-monohydroxyphylloquinone by MS analysis.     

Six 2′-hydroxyflavonols from Gutierrezia microcephala

Six 2′-hydroxyflavonols were isolated from Gutierrezia microcephala, including four new compounds, 5,7,2′-trihydroxy-3,6,4′,5′-tetramethoxyflavone, 5,7,2′-trihydroxy-3,6,8,4′,5′-pentamethoxyflavone, 5,2′-dihydroxy-3,6,7,8,4′,5′-hexamethoxyflavone and 5,7,2′,4′-tetrahydroxy-3,8,5′-trimethxoyflavone and two known compounds, 5,7,2′,5′-tetrahydroxy-3,6,8,4′-tetramethoxyflavone and 5,7,2′,4′-tetrahydroxy-3,6,8,5′-tetramethoxyflavone.     

Novel phenanthrene and isocoumarin from the rhizomes of Dioscorea nipponica Makino subsp. rosthornii (Prain et Burkill) C. T. Ting (Dioscoreaceae)

The investigation of the constituents in the rhizomes of Dioscorea nipponica Makino subsp. rosthornii (Prain et Burkill) C. T. Ting afforded one new phenanthrene 2,2′,7,7′-tetramethoxy-[1,1′-biphenanthrene]-4,4′,6,6′-tetrol (7) and one new isocoumarin diorosthornoumarin (8), together with 16 known compounds (1–6 and 9–18). Their structures were established on the basis of extensive spectroscopic evidences (IR, HR-ESI-MS, NMR and optical rotation), as well as comparison with literature values. All the compounds 1–18 were firstly isolated from Dioscorea nipponica Makino subsp. Rosthornii (Prain et Burkill) C. T. Ting, and compound 9 was firstly obtained as a natural product from plants, while the compounds 11 and 14 were obtained from both the genus Dioscorea and the family Dioscoreaceae for the first time. Moreover, the antitumor activities of the compounds were tested against lung carcinoma NCI-H460 cell line. Compound 12, 13, 15 and 16 showed significant cytotoxic activities, whereas 7 displayed moderate cytotoxicity.     

2,4,2′-Trihydroxy-4′-methoxybenzil from Zollernia paraensis

A new phenolic compound, isolated from the wood of Zollernia paraensis, has been shown to be 2,4,2′-trihydroxy-4′-methoxybenzil by spectral data and synthesis.