Isolation and characterisation of three new anthraquinone secondary metabolites from <i>Symplocos</i><i>racemosa</i>

<div><p>Three new anthraquinone secondary metabolites were isolated from <i>Symplocos racemosa</i>, a small tree of family symplocaceae. The structures of compounds (<b>1</b>–<b>3</b>) were elucidated to be 1,4-dihydroxy-6-(ethoxymethyl)-8-propylanthracene-9,10-dione (<b>1</b>), 1,4-dihydroxy-6-(hydroxymethyl)-8-butylanthracene-9,10-dione (<b>2</b>) and 1,4-dihydroxy-6-(hydroxymethyl)-8-propyl anthracene-9,10-dione (<b>3</b>) using their spectral data, i.e. through IR, UV, ¹H NMR, ¹³C NMR and two-dimensional (2D) NMR techniques including heteronuclear multiple quantum coherence, heteronuclear multiple bond correlation and correlation spectroscopy.</p></div

A new rosane-type diterpenoid from <i>Stachys parviflora</i> and its density functional theory studies

<div><p>A new rosane-type diterpenoid (<b>1</b>) has been isolated from the chloroform fraction of <i>Stachys parviflora</i>. Structure of <b>1</b> was proposed based on 1D and 2D NMR techniques including correlation spectroscopy, heteronuclear multiple quantum coherence, heteronuclear multiple bond correlation and nuclear Overhauser effect spectroscopy. A theoretical model for the electronic and spectroscopic properties of compound <b>1</b> is also developed. The geometries and electronic properties were modelled at B3LYP/6-31G^* and the theoretical scaled spectroscopic data correlate nicely with the experimental data.</p></div

Abeliaside, a new phenolic glucoside from <i>Abelia triflora</i>

<p>A new phenolic glucoside, abeliaside, along with four known compounds, 5,6,7,4′-tetrahydroxy flavones, caffeic acid, 4-<i>O</i>-caffeoylquinic acid and caffeic acid glucoside, was isolated from the leaves of <i>Abelia triflora</i> R. Br. (Caprifoliaceae). The structure of the new compound was elucidated by different spectroscopic techniques. Compounds <b>1</b>–<b>5</b> were assayed for their anticancer activities against two cancerous human cell lines, MCF-7 and PC-3 cells, and normal Vero cell line using the crystal violet staining method. From the results it could be seen that caffeic acid possessed the highest anticancer effect against MCF-7 (IC₅₀: 17 μg/mL) and PC-3 (IC₅₀: 20.1 μg/mL) compared to vinblastine sulphate as reference drug (IC₅₀: 4.6, 2.8 μg/mL). The other compounds showed weak anticancer activity on both cell lines.</p

Sweritranslactones A–C: Unusual Skeleton Secoiridoid Dimers via [4 + 2] Cycloaddition from Swertiamarin

Skeleton-diversity-oriented chemical conversion from pure natural products is a valuable method to obtain natural product-like compounds, especially those with novel architecture. The application of phytochemical methods to iridoids yielded three novel secoiridoid dimers: sweritranslactones A–C (<b>1</b>–<b>3</b>). These molecules possess a 6/6/6/6/6/6-fused hexacyclic skeleton and were obtained from swertiamarin, one of the major constituents of the genus <i>Swertia</i>, via a [4 + 2] cycloaddition and intramolecular nucleophilic addition under aqueous conditions. The structures were established based on extensive spectroscopic characterization and X-ray crystallographic diffraction analysis

New flavonol glycosides from the leaves of <i>Caragana brachyantha</i>

<div><p>Two new flavonol glycosides, brachysides C and D, together with three known flavonol glycosides, were isolated from the leaves of <i>Caragana brachyantha</i>. The structures of brachysides C and D were elucidated on the basis of detailed spectroscopic analysis as quercetin 5-<i>O</i>-[α-l-rhamnopyranosyl-(1 → 6)-β-d-glucopyranoside]-7-<i>O</i>-[α-l-rhamnopyranoside] and quercetin 5-<i>O</i>-[α-l-rhamnopyranosyl-(1 → 6)-β-d-glucopyranoside]-7-<i>O</i>-[α-l-rhamnopyranoside]-4′-<i>O</i>-[α-l-rhamnopyranoside], respectively. The presence of flavonol tetra- and triglycosides bearing a sugar moiety at position 5 was the first report from this genus <i>Caragana</i>.</p></div

Sweritranslactones A–C: Unusual Skeleton Secoiridoid Dimers via [4 + 2] Cycloaddition from Swertiamarin

Skeleton-diversity-oriented chemical conversion from pure natural products is a valuable method to obtain natural product-like compounds, especially those with novel architecture. The application of phytochemical methods to iridoids yielded three novel secoiridoid dimers: sweritranslactones A–C (<b>1</b>–<b>3</b>). These molecules possess a 6/6/6/6/6/6-fused hexacyclic skeleton and were obtained from swertiamarin, one of the major constituents of the genus <i>Swertia</i>, via a [4 + 2] cycloaddition and intramolecular nucleophilic addition under aqueous conditions. The structures were established based on extensive spectroscopic characterization and X-ray crystallographic diffraction analysis

Polyphenolic compounds from <i>Malus hupehensis</i> and their free radical scavenging effects

<p>One new 4-chromanone glycoside, 5-<i>O</i>-<i>β</i>-d-glucopyranoside-4-chromanone (<b>1</b>), together with 21 known polyphenols, was isolated from the leaves of <i>Malus hupehensis</i>. Their structures were elucidated on the basis of extensive spectroscopic methods including NMR (1D and 2D), mass (ESIMS and HRESIMS), IR, and by comparison with the data reported in the literature. Some of the isolated compounds were screened for antioxidant activity. Compounds <b>18</b> and <b>14</b> exhibited significant antioxidant activities with SC₅₀ values 2.73 and 2.91 μg/mL, respectively, while <b>17</b>, <b>19</b>, <b>11</b>, <b>7</b>, <b>20</b>, <b>22</b>, <b>12</b> and <b>13</b> exhibited moderate activities with SC₅₀ values ranging from 5.24–11.86 μg/mL. The HPLC fingerprint profiles of the leaves and fruits extracts were also analysed, which showed that the constituents were almost the same in both the extracts except for the content of phlorizin which was present in higher amount in the leaves.</p

Structural characterization and immunosuppressive activity of a new pregnane glycoside from <i>Epigynum cochinchinensis</i>

<p>Phytochemical investigation on the ethyl acetate fraction of the leaves of <i>Epigynum cochinchinensis</i> led to the isolation of a new C₂₁ pregnane glycoside, epigycoside B (<b>1</b>), together with three known analogues. Their structures were elucidated on the basis of extensive spectroscopic techniques, including UV, MS, and NMR experiments, as well as the chemical methods. Compound <b>1</b> displayed <i>in vitro</i> immunosuppressive activity against concanavalin A (Con A)/Lipopolysaccharides (LPS)-stimulated proliferation of mice splenocyte. The activity was significant as compared with control group at 50 <i>μ</i>M concentration.</p

Meroterpenoids with Antitumor Activities from Guava (<i>Psidium guajava</i>)

<i>Psidium guajava</i> L., a species native to South America, has been widely cultivated in the tropical and subtropical areas of China for its popular fruits. The preliminary analysis by liquid chromatography-ultraviolet (LC-UV) indicated the presence of meroterpenoids in the fruits of <i>P. guajava</i> (guava). Subsequent fractionation of the petroleum ether extract resulted in the identification of two new meroterpenoids, psiguajavadials A (<b>1</b>) and B (<b>2</b>), together with 14 previously described meroterpenoids (<b>3</b>–<b>16</b>). Their structures were fully elucidated by comprehensive spectroscopic techniques and theoretical calculations. All of the meroterpenoids showed cytotoxicities against five human cancer cell lines, with guajadial B (<b>12</b>) being the most effective having an IC₅₀ value of 150 nM toward A549 cells. Furthermore, biochemical topoisomerase I (Top1) assay revealed that psiguajavadial A (<b>1</b>), psiguajavadial B (<b>2</b>), guajadial B (<b>12</b>), guajadial C (<b>14</b>), and guajadial F (<b>16</b>) acted as Top1 catalytic inhibitors and delayed Top1 poison-mediated DNA damage. The flow cytometric analysis indicated that the new meroterpenoids psiguajavadials A (<b>1</b>) and B (<b>2</b>) could induce apoptosis of HCT116 cells. These data suggest that meroterpenoids from guava fruit could be used for the development of antitumor agents

New pyrazinoquinazoline alkaloids Isolated from a culture of <i>Stenotrophomonas maltophilia</i> QB-77

<p>Two new pyrazinoquinazoline alkaloids, <i>epi</i>-fiscalin D (<b>1</b>) and <i>epi</i>-fiscalin E (<b>2</b>), as well as three known analogues, norquinadoline A (<b>3</b>), quinadoline A (<b>4</b>), and fiscalin C (<b>5</b>), were isolated from ethyl acetate extract of the fermentation broth of <i>Stentrophomonas maltophilia</i> QB-77. The structures of new compounds were elucidated on the basis of extensive spectroscopic data analysis including UV, HRESIMS, and 1D and 2D NMR experiments. All the isolated compounds were tested for their <i>in vitro</i> cytotoxicity against five human cancer cell lines (SMMC-7721, MCF-7, HL-60, SW480, and A-549) and antibacterial activities against <i>Bacillus subtilis</i>, <i>Escherichia coli</i>, and <i>Staphylococcus aureus</i>.</p