Hydroxyenone Derivatives: In vitro Anti-malarial and Docking Studies against P. falciparum.

METHODS: A series of 1-{2-(prop-2-ynyloxy)aryl}-3-hydroxy-3-(4'-trifluoromethylphenyl) prop-2-en-1-ones obtained by photo-irradiation of 2-{2-(prop-2-ynyloxy)benzoyl}-3-(4- trifluorome-thyl-phenyl)oxiranes (that were characterized by spectral studies: FT-IR, 1H NMR, 13C NMR and Mass analysis) was screened for the anti-malarial activity by evaluating against chloroquine-sensitive P. falciparum (CD7). The molecular docking studies using AutoDock Vina were also performed to further ascertain the efficacy of these compounds with PDB:4ORM. RESULTS: Among these, the hydroxyenone derivatives 2b, 2c and 2a exhibited very potent antimalarial activity that was clearly evinced by the results of molecular docking. Binding energies of hydroxyenone compounds were calculated and found in the range of -10.4 to -9.0 kcal/mol. CONCLUSION: Compound 2b had the strongest binding affinity with docking score of -10.4 kcal/mol.

Photo-reorganization of 3-alkoxy-6-chloro-2-(benzo[b]thiophen-2-yl)-4H-chromen-4-ones: a green and convenient synthesis of angular pentacyclics.

Photo-reorganization of 3-alkoxy-6-chloro-2-(benzo[b]thiophen-2-yl)-4H-chromen-4-ones in methanol with Pyrex filtered UV-light from a medium pressure 125 W Hg-vapor lamp led to the formation of angular pentacyclic compounds (dihydro and aromatic products) along with some rearranged chromenones where the product(s) distribution depended upon the structure of 3-alkoxy groups (methoxy, ethoxy, allyloxy and benzyloxy). The phenyl moiety in the 3-benzyloxy group had a profound effect on the dihydro product(s) formation as the latter was in high yield when the alkoxy group was benzyloxy followed by allyloxy, ethoxy and methoxy groups. The present photochemical study represents a general method for the synthesis of some angular pentacyclic - benzothiophene fused xanthenone derivatives in a single step without using any specific and toxic reagent. The structures of the new organic scaffolds obtained were established by their spectral data (UV, IR and NMR).

Phototransformation of 3-alkoxychromenones: regioselective photocyclisation and dealkoxylation.

The phototransformation of some 2-(3-methoxyphenyl)-4H-chromen-4-ones bearing a propynyloxy moiety at the 3-position has been described. On photolysis with pyrex-filtered UV light from a Hg lamp (125 W), these chromenones produced a major amount of 5-ethynyl-2-methoxy-6-oxa-benzo[5,6-c]xanthen-7-ones consisting of an exotic tetracyclic scaffold. These photoproducts have been envisioned to be produced through regioselective ring closure at the 6'-position of the 2-(3'-methoxy)phenyl moiety of the initially formed 1,4-biradical via a γ-H abstraction mechanism. No product whatsoever was observed through ring closure at the 2'-position. This behaviour has been found to be in accordance with the directive influence observed in free radical aromatic substitutions. This regioselective photocyclisation is further supported by calculations made from 3D structures (MM2 program). In addition, during the irradiation of these substrates, 2-(3-methoxyphenyl)-4H-chromen-4-ones were also realised through dealkoxylation. The structures of the substrates and photoproduct(s) have been determined by their spectroscopic (IR, NMR, mass spectrometry) studies.

Crystal structure of (Z)-3-[5-chloro-2-(prop-2-yn-yloxy)phen-yl]-3-hy-droxy-1-[4-(tri-fluoro-meth-yl)phen-yl]-prop-2-en-1-one.

The title compound, C19H12ClF3O3, obtained by the photochemical transformation of 2-[5-chloro-2-(prop-2-yn-yloxy)benzo-yl]-3-[4-(tri-fluoro-meth-yl)phen-yl]oxirane adopts a Z conformation with respect to the enolic C=C double bond. The dihedral angle between the benzene rings is 12.25 (16)° and an intra-molecular O-H⋯O hydrogen bond closes an S(6) ring. An intra-molecular C-H⋯O inter-action also leads to an S(6) ring. In the crystal, very weak C-H⋯O inter-actions and short Cl⋯Cl contacts [3.3221 (16) Å] are seen, as well as weak aromatic π-π stacking inter-actions [centroid-centroid separation = 3.879 (2) Å].

Absorption and Fluorescent Studies of 3-Hydroxychromones.

The synthesis and spectral studies of variously substituted 3-hydroxychromones have been carried out. A key relationship between the structural motif of synthesized 3-hydroxychromones (3-HCs) and their fluorescent properties was found. The chromones substituted with electron-donating group at 4'-position expressed the red shift of the N(*) and T(*) band and also exhibited the increased fluorescent intensity ratio while the chromones with electron-withdrawing group showed the blue shift of the N(*) and T(*) band. Therefore, these 3-HCs may behave as the possible fluorescent probes.

One-shot photochemical synthesis of 5-(thiophen-3-yl)pyrano[2,3-c]chromen-2(3H)-ones from 3-propynyloxy-chromenones: a case of an intramolecular Paterno-Buchi reaction.

5-(Thiophen-3-yl)pyrano[2,3-c]chromen-2(3H)-ones (2), angular tricyclic compounds, were synthesized in significantly high yields through the photoinduced intramolecular coupling of the acetylenic group with the carbonyl centre in 3-(prop-2-ynyloxy)-2-(thiophen-3-yl)-4H-chromen-4-ones (1). This photoreaction is a case of an intramolecular Paterno-Buchi reaction and is unprecedented in 3-propynyloxy-chromenones. The structure of 2 has been determined by spectroscopic (FTIR, NMR and mass) and single crystal X-ray crystallographic studies.

Synthesis of spiropyrans: H-abstractions in 3-cycloalkenyloxybenzopyrans.

A photochemical route for the synthesis of some benzopyronospiropyrans from 2-furyl-3-cycloalkenyloxybenzopyrones involving H-abstraction is reported. How a methyl group on the furyl ring affects the product formation is also investigated.

Inhibition of inosine monophosphate dehydrogenase (IMPDH) by 2-[2-(Z)-fluorovinyl]inosine 5'-monophosphate.

Inosine 5'-monophosphate dehydrogenase (IMPDH; EC 1.1.1.205) isolated from Escherichia coli B3 cells was strongly inhibited by 2-[2-(Z)-fluorovinyl]inosine 5'-monophosphate (2-FVIMP). Inhibition of IMPDH appears to be irreversible with k(inact) and K(i) values of 0.0269 s(-1) and 1.11 microM, respectively.

Purification and characterization of cathepsin L-like proteinase from goat brain.

Cathepsin L-like proteinase was purified approximately 1708-fold with 40% activity yield to an apparent electrophoretic homogeneity from goat brain by homogenization, acid-autolysis at pH 4.2, 30-80% (NH4)2SO4 fractionation, Sephadex G-100 column chromatography and ion-exchange chromatography on CM-Sephadex C-50 at pH 5.0 and 5.6. The molecular weight of proteinase was found to be approximately 65,000 Da, by gel-filtration chromatography. The pH optima were 5.9 and 4.5 for the hydrolysis of Z-Phe-Arg-4mbetaNA (benzyloxycarbonyl-L-phenylalanine-L-arginine-4-methoxy-beta-naphthylamide) and azocasein, respectively. Of the synthetic chromogenic substrates tested, Z-Phe-Arg-4mbetaNA was hydrolyzed maximally by the enzyme (Km value for hydrolysis was 0.06 mM), followed by Z-Val-Lys-Lys-Arg-4mbetaNA, Z-Phe-Val-Arg-4mbetaNA, Z-Arg-Arg-4mbetaNA and Z-Ala-Arg-Arg-4mbetaNA. The proteinase was activated maximally by glutathione in conjunction with EDTA, followed by cysteine, dithioerythritol, thioglycolic acid, dithiothreitol and beta-mercaptoethanol. It was strongly inhibited by p-hydroxymercuribenzenesulphonic acid, iodoacetic acid, iodoacetamide and microbial peptide inhibitors, leupeptin and antipain. Leupeptin inhibited the enzyme competitively with Ki value 44 x 10(-9) M. The enzyme was strongly inhibited by 4 M urea. Metal ions, Hg(2+), Ca(2+), Cu(2+), Li(2+), K(+), Cd(2+), Ni(2+), Ba(2+), Mn(2+), Co(2+) and Sn(2+) also inhibited the activity of the enzyme. The enzyme was stable between pH 4.0-6.0 and up to 40 degrees C. The optimum temperature for the hydrolysis of Z-Phe-Arg-4mbetaNA was approximately 50-55 degrees C with an activation energy Ea of approximately 6.34 KCal mole(-1).

Effects of some antituberculous and anti-leprotic drugs on cathepsins B, H and L.

The cysteine proteinases like cathepsins B, L and H are main hydrolytic enzymes present in lysosomes and play an important role in intracellular protein degradation. Tuberculosis and leprosy, both are tissue- destructive diseases. Main drugs used in chemotherapy of these diseases may inhibit the main lysosomal cysteine proteinases i.e. cathepsins B, L and H released during tissue destruction and thus prevent the further destruction of tissue by these enzymes. So the aim of this study is to see the effect of antituberculous and antileprotic drugs on these proteolytic enzymes. The effect of commonly used antituberculous and antileprotic drugs was screened on the activities of purified brain lysosomal cysteine proteinases namely cathepsins B [EC 3.4.22.1], L [EC 3.4.22.15] and H [EC 3.4.22.16]. Among the antileprotic drugs, only clofazimine inhibited the enzymic activities whereas dapsone had no effect whatsoever. In antituberculous drugs, rifampicin was the most inhibitory while isoniazid had little inhibitory potency. Streptomycin and pyrazinamide did not effect the activities at all. As regards the mechanism of inhibition, clofazimine and isoniazid inhibited the enzymes in a non-competitive manner with K values of 0.25 mM and 5.0 mM for cathepsin B, 0.071 mM and 0.833 mM for cathepsin L and 1.513 mM and 0.885 mM for cathepsin H, While rifampicin could effect in a competitive manner with K(i) values of 0.03 mM, 0.125 mM and 0.027 mM for cathepsin B, L and H respectively.