Nawong Boonnak

Nitric Oxide Inhibitory Activity of Xanthones from the Green Fruits of Cratoxylum formosum ssp. pruniflorum

Three new xanthones, pruniflorone M-O (1–3), and a new xanthonolignoid, 3-methoxy-5′-demethoxycadensin G (4), were isolated from the green fruits of Cratoxylum formosum ssp. pruniflorum along with three known xanthones (5–7) and a known flavonoid (8). Their structures were elucidated by spectroscopic methods and the structure of 1 was also determined by X-ray crystallography. Compounds 2 and 7 showed potent nitric oxide inhibitory activity with IC50 values of 4.4 and 4.3 μM, respectively. Moreover, 7 also showed strong antibacterial activity against both Gram-positive and Gram-negative bacteria with an MIC value of 4.67 μg mL–1.

Three types of cytotoxic natural caged-scaffolds: pure enantiomers or partial racemates.

Two rare new natural products, the neocaged-xanthone pruniflorone T (1) and the rearranged caged-xanthone pruniflorone U (3), and the known caged-xanthone cochinchinone C (2) were isolated from the roots of Cratoxylum formosum ssp. pruniflorum. The unique structures of 1-3 were determined by analysis of NMR and X-ray diffraction data. The X-ray data of 1-3 revealed that they all exist with both enantiomers in their crystal packing. Separation of 1-3 by chiral HPLC led to the isolation of three pairs of enantiomers, (-)-1/(+)-1, (-)-2/(+)-2, and (-)-3/(+)-3, and their absolute configurations were determined by analysis of single-crystal X-ray diffraction and ECD spectroscopic data. A 1:1 mixture of 1 and 3 showed potent in vitro cytotoxicity against an MCF-7 human breast cancer cell line with an IC50 value of 0.11 μg/mL.

1-(2,4-Dinitrophenyl)-2-[(E)-2,4,5-trimethoxybenzylidene]hydrazine

The title compound, C16H16N4O7, is close to being planar, with a dihedral angle of 3.15 (11)° between the benzene rings. The methoxy groups at the ortho- and para-positions of the 2,4,5-trimethoxyphenyl group are almost coplanar with the ring [deviations of the C atoms = 0.017 (2) and −0.025 (2) Å, respectively], whereas the meta-methoxy group deviates slightly [C-atom displacement = 0.162 (2) Å]. Both the ortho- and para-nitro groups are close to being coplanar with their attached ring [dihedral angles = 7.81 (12) and 8.56 (11)°, respectively]. An intramolecular N—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, inversion dimers linked by pairs of N—H⋯O hydrogen bonds involving the same H atom as the intramolecular bond generate R 2 2(12) loops. The dimers are linked by weak C—H⋯O interactions into sheets parallel to the (10-4) plane and the sheets are stacked by π–π interactions, with a centroid–centroid distance of 3.5974 (14) Å.

Redetermination and absolute configuration of pruniflorone M monohydrate

The title xanthone known as pruniflorone M (systematic name: (2R)-5,10-dihydroxy-2-hydroxymethyl-1,1-dimethyl-1H-furo[2,3-c]xanthen-6-one), crystallized in a monohydrate form, C18H16O6·H2O. It was isolated from the green fruits of Cratoxylum formosum ssp. pruniflorum. The structure of the title compound has been reported previously [Boonnak et al. (2010 ▶). Aust. J. Chem. 63, 1550–1556], but we report here the absolute configuration determined using Cu Kα radiation. There are two crystallograpically independent molecules in the asymmetric unit, which differ slightly in the bond angles. The hydroxymethyl substituents at position 2 of the furan rings of both pruniflorone M molecules adopt R configurations. In both molecules, the three rings of the xanthone skeleton are approximately coplanar, with an r.m.s. deviation of 0.0124 (2) Å for one molecule and 0.0289 (2) Å for the other, and the furan ring adopts an envelope conformation. In the crystal, molecules of pruniflorone M and water are linked into a two-dimensional network by O—H⋯O hydrogen bonds and weak C—H⋯O interactions. The crystal structure is further consolidated by π–π interactions with centroid–centroid distances in the range 3.5987 (13)–3.7498 (14) Å. Short C⋯C [3.378 (3) Å] and O⋯O [2.918 (3) Å] contacts are also observed.

4-[(E)-(4-Eth­oxy­benzyl­idene)amino]­phenol

The molecule of the title compound, C15H15NO2, adopts a trans conformation with respect to the methylidene C=N bond and is twisted with a dihedral angle of 26.31 (5)° between the two substituted benzene rings. The ethoxy group is almost coplanar with the bound benzene ring with a C—O—C—C torsion angle of −179.08 (9)°. In the crystal, molecules are linked by O—H⋯N hydrogen bonds and weak C—H⋯O interactions into chains propagating in the [011] and [01-1] directions. C—H⋯π interactions are also present.

4-Bromo-N-phenyl­benzamide

The molecule of the title benzamide derivative, C13H10BrNO, is twisted with the dihedral angle between the phenyl and 4-bromophenyl rings being 58.63 (9)°. The central N—C=O plane makes dihedral angles of 30.2 (2) and 29.2 (2)° with the phenyl and 4-bromophenyl rings, respectively. In the crystal, molecules are linked by N—H⋯O hydrogen bonds into chains along [100]. C—H⋯π contacts combine with the N—H⋯O hydrogen bonds, to form a three-dimensional network.

Anti-HIV-1 integrase activity and molecular docking of compounds from Albizia procera bark.

Abstract Context: Albizia procera (Roxb.) Benth. (Mimosaceae) has been traditionally used in Thai longevity preparations. Thus, searching for HIV-1 integrase (HIV-1 IN) agents from natural sources is of interest. Objective: The objective of this study is to examine the inhibitory activity against HIV-1 IN of compounds isolated from the stem bark of Albizia procera. Materials and methods: The EtOH extract and isolated compounds of Albizia procera bark were examined for anti-HIV-1 IN activity at various concentrations (10–100 µg/mL and 10–100 µM) using the multiplate integration assay and molecular docking. Results and discussions: The results showed that the ethanol extract had good anti-HIV-1 IN activity with an IC50 value of 19.5 µg/mL, whereas ethyl acetate fraction exhibited the most potent with an IC50 value of 19.1 µg/mL, followed by water fraction (IC50 value = 21.3 µg/mL), hexane and chloroform fractions (IC50 value > 100 µg/mL), respectively. From bioassay-guided isolation, the ethyl acetate fraction was further separated to give two compounds which are (+)-catechin (1) and protocatechuic acid (2), respectively. Of the tested samples, (+)-catechin (1) exhibited appreciable activity against HIV-1 IN with an IC50 value of 46.3 µM, whereas protocatechuic acid (2) showed mild activity with 46.0% inhibition at concentration of 100 µM. (+)-Catechin (1) could interact with Thr66, Gly148, and Glu152 in the core domain of IN enzyme, whereas protocatechuic acid (2) could bind with Thr66, His67, Glu152, Asn155, and Lys159. This is the first report on anti-HIV-1 IN activity of Albizia procera bark. These results may suggest that Albizia procera bark has potential as anti-HIV-1 IN agent.

1-Methyl-2-((1E,3E)-4-phenylbuta-1,3-dienyl)pyridinium iodide: Synthesis, characterization, and X-ray analysis

Abstract1-Methyl-2-((1E,3E)-4-phenylbuta-1,3-dienyl)pyridinium iodide (1) is synthesized and characterized by UV-Vis, FT-IR, 1H and 13C NMR, and single crystal X-ray diffraction. Compound 1 crystallizes in an orthorhombic Iba2 space group with the unit cell parameters a = 12.8236(11) Å, b = 20.1216(17) Å, c = 11.2071(10) Å, V = 2891.8(4) Å3 and Z = 8. X-ray diffraction indicates that the molecule of 1 displays E,E configurations with respect to the two middle C=C double bonds. The molecular structure of 1 is twisted and the dihedral angle between the pyridinium and phenyl rings is 15.0(2)°. In the crystal packing, cations form stacks in an anti-parallel V-shaped manner along the a axis through π-π interactions between pyridinium and phenyl rings.

(E)-2-[(2,4,6-Tri-meth-oxy-benzyl-idene)amino]-phenol.

There are two independent molecules in the asymmetric unit of the title compound, C16H17NO4, with similar conformations but some differences in their bond angles. Each molecule adopts a trans configuration with respect to the methylidene C=N bond and is twisted with a dihedral angle between the two substituted benzene rings of 80.52 (7)° in one molecule and 83.53 (7)° in the other. All methoxy groups are approximately coplanar with the attached benzene rings, with Cmethyl—O—C—C torsion angles ranging from −6.7 (2) to 5.07 (19)°. In the crystal, independent molecules are linked together by O—H⋯N and O—H⋯O hydrogen bonds and a π–π interaction [centroid–centroid distance of 3.6030 (9) Å], forming a dimer. The dimers are further linked by weak C—H⋯O interactions and another π–π interaction [centroid–centroid distance of 3.9452 (9) Å] into layers lying parallel to the ab plane.

2,2'-[2,4-Bis(naphthalen-1-yl)cyclo-butane-1,3-di-yl]bis-(1-methyl-pyridinium) bis-(4-chloro-benzene-sulfonate): thermal-induced [2 + 2] cyclo-addition reaction of a heterostilbene.

The asymmetric unit of the title salt, C36H32N2 2+·2C6H4ClO3S−, consists of one anion and one half-cation, the other half being generated by inversion symmetry. The dihedral angle between the pyridinium ring and the napthalene ring system in the asymmetric unit is 42.86 (6)°. In the crystal, cations and anions are linked by weak C—H⋯O interactions into chains along [010]. Adjacent chains are further arranged in an antiparallel manner into sheets parallel to the bc plane. π–π interactions are observed involving the cations, with centroid–centroid distances of 3.7664 (8) and 3.8553 (8) Å.