Key HMBC, ¹H-¹H COSY, and ROESY correlations of 1.

<p>Key HMBC, ¹H-¹H COSY, and ROESY correlations of 1.</p

¹H NMR spectra comparison of rubipodanin A (1, top) and RA-V (4, bottom).

<p>¹H NMR spectra comparison of rubipodanin A (1, top) and RA-V (4, bottom).</p

Chemical structures of 1–7.

<p>Chemical structures of 1–7.</p

New Labdane diterpenes from <i>Hedychium yunnanense</i> with cytotoxicity and inhibitory effects on nitric oxide production

<p>Two new labdane diterpenes, hedychenoids A (<b>1</b>) and B (<b>2</b>), were isolated from the rhizomes of <i>Hedychium yunnanense</i>, together with four known ones hedychenone (<b>3</b>), forrestin A (<b>4</b>), villosin (<b>5</b>) and calcaratarin C (<b>6</b>). Their structures were determined on the basis of NMR (1D and 2D) and mass spectroscopic analysis. Compounds <b>2</b>, <b>3</b> and <b>5</b> exhibited cytotoxicity against SGC-7901 with IC₅₀ values of 14.88 ± 0.52, 7.08 ± 0.21 and 7.76 ± 0.21 μg/ml, <b>3</b> and <b>5</b> against HeLa with IC₅₀ values of 9.76 ± 0.48 and 13.24 ± 0.63 μg/ml, respectively. Compounds <b>2</b>, <b>5</b> showed inhibitory effects against nitric oxide production in LPS and IFN-γ-induced RAW 264.7 murine macrophages with IC₅₀ values of 6.57 ± 0.88 and 5.99 ± 1.20 μg/ml, respectively.</p

New Cytotoxic Naphthohydroquinone Dimers from <i>Rubia alata</i>

Two novel naphthohydroquinone dimers with unprecedented skeletons, rubialatins A (<b>1</b>) and B (<b>2</b>), were isolated from the herbal plant <i>Rubia alata</i> together with their precursor, mollugin (<b>3</b>). The structures were elucidated on the basis of NMR spectra and crystal X-ray diffraction. Compound <b>1</b>, a racemate, was separated by chiral column chromatography, and the absolute configurations of the enantiomers were determined by the computational methods. Cytotoxicity of <b>1</b>–<b>3</b> was evaluated as well as the effect on the NF-κB pathway. Compound (+)-<b>1</b> showed cytotoxicity and could inhibit NF-κB pathway. Meanwhile, <b>2</b> showed cytotoxicity and a synergistic effect with TNF-α on NF-κB activation

Biologically Active Arborinane-Type Triterpenoids and Anthraquinones from <i>Rubia yunnanensis</i>

Twelve new arborinane-type triterpenoids (<b>1</b>–<b>12</b>) and four new anthraquinones (<b>13</b>–<b>16</b>), together with 50 known compounds, were isolated from the roots of <i>Rubia yunnanensis</i>. The structures of <b>1</b>–<b>16</b> were elucidated by spectroscopic data analysis and chemical methods. All compounds were evaluated for their cytotoxic, antibacterial, and antifungal activities. Rubiyunnanol C (<b>5</b>) is the first example of an arborinane-type triterpenoid with a double bond at C-8–C-9

Isolation of novel peptides (MCh-1 and MCh-2) from <i>M. charantia</i> and sequence comparison with related peptides.

<p>(A) RP-HPLC trace of the crude peptide extract from <i>M. charantia</i> seeds showing the retention times and relative intensities of the different peptides. The gradient was 1% solvent B linear for 70 min at 3 mL/min. (B) Alignment of the sequences of MCh-1, MCh-2, MCo-1 to MCo-6 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0075334#pone.0075334-Chan1" target="_blank">[27]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0075334#pone.0075334-Chan2" target="_blank">[39]</a>, MCTI-I <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0075334#pone.0075334-Hara1" target="_blank">[4]</a>, MCTI-II <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0075334#pone.0075334-Hara1" target="_blank">[4]</a>, MCTI-III <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0075334#pone.0075334-Hamato1" target="_blank">[5]</a>, EETI-II <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0075334#pone.0075334-LeNguyen1" target="_blank">[19]</a> and MCoTI-II <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0075334#pone.0075334-Hernandez1" target="_blank">[40]</a>. Cysteine residues (numbered I–VI) are highlighted in bold and the backbone loops are numbered 1–6.</p

Reductive unfolding and oxidative refolding of MCh-1.

<p>(A) RP-HPLC trace of the selective reduction of MCh-1 using 0.1 M TCEP in 0.2 M citrate buffer at pH 3.5 at 65°C under nitrogen after 3 min. The elution positions of the fully reduced (R), the species with two disulfide bonds (IIa) and the native MCh-1 (N) are indicated. The gradient was 5% solvent B for 5 min, 5–80% solvent B linear at 0.3 mL/min in 40 min. (B & C) LCMS profiles of the refolding of the reduced MCh-1. Oxidative refolding was performed in 50% isopropyl alcohol, 0.1 M ammonium bicarbonate (pH 8.5) either with 1 mM GSH or not at room temperature. An equal volume of aliquots was withdrawn at different time points, quenched with an equal volume of 4% aqueous TFA, and analyzed by RP-HPLC and LCMS. The samples were stored at –20°C. “R” and “N” indicate the elution positions of the fully reduced and native MCh-1. “Ia” and “IIa” denote the partially reduced intermediates containing one (CysIII-CysVI) and two (CysII-CysV and CysIII-CysVI) disulfide bonds respectively. The gradient was 5% solvent 2 for 5 min, 5–35% solvent 2 linear at 0.3 mL/min in 60 min. (D) LCMS profiles of the refolding of IIa (Experimental conditions are same as C). “▾, •, ★, and ▪” indicate the three-disulfide, two-disulfide, and one-disulfide scrambled isomers, and fully reduced MCh-1, respectively.</p

MS/MS spectra of (A) the doubly charged ion <i>m/z</i> 1141.32 and (B) its +18 adduct ion <i>m/z</i> 1150.32 from the digestion of the alkylated IIa.

<p>The partial sequence of the peptide, alkylation type and position, the detected b- and y- series of ions are shown. “b and y” designate ions having the charge retained on the N-terminal fragment and the C-terminal fragment, respectively.</p

This schematic diagram represents the different folds of MCh-1 intermediates.

<p>This schematic diagram represents the different folds of MCh-1 intermediates.</p