Rukamtenol, a new spiro compound isolated from Flacourtia rukam Zoll. & Moritzi growing in Vietnam.

Chemical investigation of chloroform extract of Flacourtia rukam Zoll. & Moritzi stems led to the isolation of one new compound namely rukamtenol together with four known compounds, viz., chaulmooric acid, flacourtin, 3,4,5-trimethoxyphenyl ß-D-glucopyranoside, and daucosterol. Their structures and relative stereochemistry have been determined by 1D and 2D NMR analysis, high resolution mass spectroscopy, and compared with those in literatures. Rukamtenol represented the first 2-oxaspiro[4.4]non-8-en-3-one in nature. The relative configuration of rukamtinol was defined using DFT-NMR chemical shift calculations and subsequent DP4 probability method. Rukamtenol, flacourtin, and 3,4,5-trimethoxyphenyl ß-D-glucopyranoside were tested for cytotoxic activity toward three MDA-MB-231, HepG2, and RD cancer cell lines. However, they failed to reveal any activity (IC50 > 100 µM) on these cell lines.

A new 26-norlanostane from Phlogacanthus turgidus growing in Vietnam.

Chemical investigation on chloroform extract of Phlogacanthus turgidus led to the isolation of one new compound namely turgidol, together with five known triterpenoids, lupeol, lupenone, betulin, betulinic acid, and taraxerol. Their structures and stereochemistry have been determined by 1 D and 2 D NMR analysis, high resolution mass spectrometry, and compared with those in literatures. The relative configuration of turgidol was defined using DFT-NMR chemical shift calculations and subsequent DP4+ probability method. Turgidol, betulin, and betulinic acid were evaluated for cytotoxic activity toward K562 cancer cell line and the alpha-glucosidase inhibition.

Nervione, a new benzofuran derivative from Nervilia concolor.

A new benzofuran derivative, nervione (1), was isolated from Nervilia concolor (Blume) Schltr. (Orchidaceae). Eight previously reported compounds were also isolated: 5,7-dimethoxyflavone (2), 3,5,7-trimethoxyflavone (3), 7-methoxyflavone (4), 3,7-dimethoxy-5-hydroxyflavone (5), tetramethylscutellarein (4',5,6,7-tetramethoxyflavone) (6), 5,7-dimethoxy-4'-hydroxyflavone (7), rhamnetin (8), and 5,7-dihydroxy-3',4'-dimethoxyflavone (9). The structures were elucidated by 1D, 2D NMR, and HRESIMS spectroscopy in addition to the literature. The relative configuration of 1 was defined using DP4+ probability while its absolute configuration was defined by comparison of the ECD spectrum of 1 with those of previously reported compounds. All isolated compounds were evaluated for alpha-glucosidase inhibition, revealing weak or no activity.[Formula: see text].

Manilkzapotane, a novel dimeric alkylresorcinol derivative from the stem bark of Manilkara zapota.

A novel dimeric alkylresorcinol derivative, manilkzapotane (1), along with seven known compounds, lupeol acetate (2), lupeol (3), arjunolic acid (4), ergosterol peroxide (5), taraxerol (6), hederagonic acid (7), and glochidiol (8) were isolated from the stem bark of Manilkara zapota. Their structures were determined on the basis of spectroscopic data. DFT-NMR chemical shift calculations and a modified probability (DP4+) method were applied to define the relative configuration of 1. To the best of our knowledge, this represents the first isolation of a dimeric alkylresorcinol derivative from the Sapotaceae family.

Atypical Lindenane-Type Sesquiterpenes from Lindera myrrha.

Two new lindenane sesquiterpenes were obtained from the roots of Lindera myrrha. These compounds were structurally elucidated by HRMS data, extensive NMR analyses, and comparison between experimental and theoretical 13C-NMR data. Myrrhalindenane A is the first monomeric seco-d lindenane displaying a non-rearranged, cyclohexanic C-ring. Myrrhalindenane B is the second occurrence of an angular lindenane-sesquiterpene related to a C6-C7 lactonization.

Antioxidant Motifs in Flavonoids: O-H versus C-H Bond Dissociation.

Flavonoids provide potential health benefits due to their antioxidant properties. The antioxidant activity of natural flavonoids is primarily exerted by phenolic hydroxyl groups; however, C-H bonds also contribute to these properties. In this study, the contributions of phenolic groups and C-H bonds to the antioxidant properties of 13 flavonoids were investigated by using the (RO)B3LYP/6-311++G(2df,2p)//B3LYP/6-311G(d,p) model chemistry in the gas phase and water and ethanol solvents. It was found that the C-H bonds have lower bond dissociation energies than O-H bonds in the 4-carbonyl and/or 3-hydroxyl group containing flavonoids and hence define antioxidant activity. The HOO· radical scavenging of the selected flavonoids is also investigated in detail through the potential energy surface, natural bond orbitals, and kinetic calculations. It was found that the favored radical scavenging mechanism of the flavonoids is hydrogen atom transfer, with the gas phase rate constants in the range of 7.23 × 103-2.07 × 109 L·mol-1·s-1. The results suggest that the flavonoids, isomelacacidin, isoteracacidin, melacacidin, and teracacidin, have antioxidant properties as high as typical phenolic compounds such as quercetin, trans-resveratrol, trolox, and ascorbic acid.

A sesquiterpenoid tropolone and 1,2,3,4-tetrahydronaphthalene derivatives from Olax imbricata roots.

The methanol extract of Olax imbricata roots afforded one new sesquiterpenoid tropolone and three new 1,2,3,4-tetrahydronaphthalene derivatives, olaximbrisides A-D (1-4). Their structures were determined by 1D and 2D NMR experiments in combination of HRESIMS. The relative configurations were assigned by the NOESY experiments. The absolute configurations were established by a combination of X-ray diffraction analysis and electronic circular dichroism (ECD) experiments. All isolated compounds were evaluated for their cytotoxic effects against some cancer cell lines. Among them, compound 1 exhibited the cytotoxicities against MCF-7, HepG2 and LU cell lines with IC50 values of 16.3, 34.3 and 8.0 µM, respectively.

Insights into the cooperativity between multiple interactions of dimethyl sulfoxide with carbon dioxide and water.

Interactions of dimethyl sulfoxide with carbon dioxide and water molecules which induce 18 significantly stable complexes are thoroughly investigated. An addition of CO2 or H2 O molecules into the DMSO⋯1CO2 and DMSO⋯1H2 O systems leads to an increase in the stability of the resulting complexes, in which it is larger for a H2 O addition than a CO2 . The overall stabilization energy of the DMSO⋯1,2CO2 is mainly contributed by the S=O⋯C Lewis acid-base interaction, whereas the O - H⋯O hydrogen bond plays a significant role in stabilizing complexes of DMSO⋯1,2H2 O and DMSO⋯1CO2 ⋯1H2 O. Remarkably, the complexes of DMSO⋯2H2 O are found to be more stable than DMSO⋯1CO2 ⋯1H2 O and DMSO⋯2CO2 . The level of the cooperativity of multiple interactions in ternary complexes tends to decrease in going from DMSO⋯2H2 O to DMSO⋯1CO2 ⋯1H2 O and finally to DMSO⋯2CO2 . It is generally found that the red shift of the O - H bond involved in an O - H⋯O hydrogen bond increases while the blue shift of a C - H bond in a C - H⋯O hydrogen bond decreases when a cooperative effect occurs in ternary complexes as compared to those of the corresponding binary complexes. © 2018 Wiley Periodicals, Inc.