Potent α-glucosidase inhibitory activity of compounds isolated from the leaf extracts of Uvaria hamiltonii

The phytochemical investigation of the leaf extracts of Uvaria hamiltonii (Annonaceae) led to the isolation and identification of ten compounds including a new seco-cyclohexene (1) together with nine known compounds (2-10). Their structures were elucidated by intensive analysis by spectroscopic methods and comparisons of their spectroscopic data with those of compounds reported in the literature. Compounds 2, 8, and 9 showed potent α-glucosidase inhibitory activity with the IC50 values ranging from 2.6-7.1 µM

Indizoline1

The title compound [systematic name: 1-meth­oxy-2-(3-methyl­but-2-en­yl)-9H-carbazole-3-carbaldehyde], C19H19NO2, is a natural carbazole which was isolated from the twigs of Clausena lansium. The carbazole ring system is essentially planar with a mean deviation of 0.0068 (10) Å. The aldehyde substituent is approximately co-planar with the attached benzene ring with a torsion angle of −8.58 (14)°, whereas the meth­oxy group is rotated out of the benzene plane with a torsion angle of −82.17 (11)°. The dihedral angle between the mean planes of the 3-methyl-2-butenyl group and the carbazole ring is 88.06 (5)°. An inter­molecular N—H⋯O inter­action connects the mol­ecules into a chain along the a axis. The crystal is further consolidated by a C—H⋯O hydrogen bond and two π–π inter­actions with centroid–centroid distances of 3.6592 (6) and 3.7440 (6) Å

5-Hy­droxy-8,8-dimethyl-10-(2-methyl­but-3-en-2-yl)-2H,6H-7,8-dihydro­pyrano[3,2-g]chromene-2,6-dione

In the title compound, C19H20O5, the pyran ring is in an envelope conformation, whereas the benzene and dihydro­pyran ring system is planar with an r.m.s. deviation of 0.0190 (1) Å. The hy­droxy group is coplanar with the attached benzene ring [r.m.s. deviation = 0.0106 (1) Å]. An intra­molecular O—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, mol­ecules are linked into chains along the b axis by weak C—H⋯O inter­actions. These chains are stacked along the a axis. C—H⋯π and weak π–π inter­actions [centroid–centroid distance = 3.7698 (7) Å] are also observed

Glycozolidal

The title compound known as glycozolidal (systematic name: 2,7-dimeth­oxy-9H-carbazole-3-carbaldehyde), C15H13NO3, is a naturally occurring carbazole, which was isolated from the roots of Clausena lansium. The carbazole ring system is essentially planar, with an r.m.s. deviation of 0.0093 (1) Å. In the crystal, inter­molecular N—H⋯O hydrogen bonds connect the mol­ecules into a chain along the c axis. C—H⋯O, C—H⋯π and π–π inter­actions, with centroid–centroid distances of 3.5924 (6), 3.6576 (6) and 3.8613 (6) Å, are also observed

2-Hy­droxy-7-meth­oxy-9H-carbazole-3-carbaldehyde

The title compound, C14H11NO3, was isolated from the roots of Clausena wallichii. The carbazole ring system is approx­imately planar (r.m.s. deviation = 0.039 Å) and the dihedral angle between the two benzene rings is 4.63 (7)°. An intra­molecular O—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, mol­ecules are linked into a zigzag network extending parallel to the ac plane by O—H⋯N and N—H⋯O hydrogen bonds

Resolution and identification of scalemic caged xanthones from the leaf extract of Garcinia propinqua having potent cytotoxicities against colon cancer cells

A new scalemic 8,8a-dihydro caged xanthone (1) was isolated from the leaf extract of Garcinia propinqua. Five other known natural products, the three caged xanthones (2, 5 and 6) and the two neocaged xanthones, (3 and 4) were also isolated as scalemic mixtures. Their structures were characterized by spectroscopic methods. The enantiomeric ratios (er) of compounds 1-6 ranged from 1:0.7 to 1:0.9. These compounds were also resolved by semipreparative chiral HPLC. The absolute configurations of (+)-2 and (+)-3 were determined by single-crystal X-ray diffraction analysis using Cu Kα radiation while the absolute configurations of the other compounds were determined by comparisons of their ECD spectra. Compounds (-)-4, (+)-4, (-)-5, (+)-5, and (-)-6 showed potent cytotoxicities against a colon cancer cell line HCT116 with IC50 values of 2.60, 7.02, 1.47, 3.37, and 4.14μM, respectively, which were better than the standard control doxorubicin (IC50 9.74μM)

Absolute configuration of micromelin

The title compound {systematic name: 7-meth­oxy-6-[(1R,2R,5R)-5-methyl-4-oxo-3,6-dioxabicyclo­[3.1.0]hexan-2-yl]-2H-chromen-2-one}, C15H12O6, is a coumarin, which was isolated from the roots of Micromelum glanduliferum. There are two mol­ecules in the asymmetric unit with slight differences in bond angles. In both mol­ecules, the furan ring adopts a flattened envelope conformation. In the crystal, mol­ecules are linked by weak C—H⋯O inter­actions into chains along the a axis. Aromatic π–π stacking inter­actions with centroid–centroid distances in the range 3.6995 (11)–3.8069 (11) Å and C⋯O short contacts [3.030 (2)–3.171 (3) Å] also occur

Styryllactones from Goniothalamus tamirensis

The phytochemical investigation of the twig and leaf extracts of Goniothalamus tamirensis led to the isolation and identification of 15 compounds including three rare previously undescribed styryllactones, goniotamirenones A-C, together with 12 known compounds. (Z)-6-Styryl-5,6-dihydro-2-pyranone and 5-(1-hydroxy-3-phenyl-allyl)-dihydro-furan-2-one are reported here for the first time as previously undescribed natural products. Their structures were elucidated by spectroscopic methods. Goniotamirenone A was synthesized via a [2 + 2] cycloaddition reaction of 6-styrrylpyran-2-one in quantitative yield. The absolute configurations of goniotamirenones B and C were identified from experimental and calculated ECD data, while the absolute configurations of (−)-5-acetoxygoniothalamin, (−)-isoaltholactone, parvistone E, and 5-(1-hydroxy-3-phenyl-allyl)-dihydro-furan-2-one were identified by single-crystal X-ray diffraction analysis using Cu Kα radiation. The absolute configurations of the other related compounds were determined from comparisons of their ECD spectra with relevant compounds reported in the literature. (−)-5-Acetoxygoniothalamin exhibited potent cytotoxicity against the colon cancer cell line (HCT116) with an IC50 value of 8.6 μM which was better than the standard control (doxorubicin, IC50 = 9.7 μM), while (Z)-6-styryl-5,6-dihydro-2-pyranone was less active with an IC50 value of 22.1 μM

1-(2,6-Dihydr­oxy-4-methoxy­phen­yl)-3-phenyl­propan-1-one1

The title compound, C16H16O4, a dihydro­chalcone, was isolated from the rhizomes of Etlingera littoralis. The mol­ecule is twisted with a dihedral angle of 71.69 (6)° between the two aromatic rings. The propanone unit makes dihedral angles of 4.07 (6) and 73.56 (7)°, respectively, with the 2,6-dihydroxy-4-methoxyphenyl and phenyl rings. The meth­oxy group is approximately coplanar with the attached benzene ring with a dihedral angle of 1.74 (10)°. An intra­molecular O—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, inter­molecular O—H⋯O hydrogen bonds link the mol­ecules into chains along [201]. A π–π inter­action with a centroid–centroid distance of 3.5185 (6) Å is also observed