Hydroxypropyl-ß-Cyclodextrin Complexes of Styryllactones Enhance the Anti-Tumor Effect in SW1116 Cell Line.

Styryllactones, a class of compounds obtained from the genus Goniothalamus (Annonaceae), have demonstrated in vitro antitumor activity. However, the aqueous solubility of these compounds is poor. In this study, we identified the absolute configurations of the previously isolated compounds, which were first isolated in our laboratory, by single-crystal X-ray diffraction analysis using Cu Kα radiation. Subsequently, the antitumor activities of the compounds were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide staining in four tumor cell lines. The induced apoptosis activity of leiocarpin E-7'-Monoacetate was studied by an annexin V fluorescein isothiocyanate/propidium iodide double-staining experiment, and the caspase activity was tested in the SW1116 cell line. The results demonstrated that the antitumor activities of cheliensisin A and goniodiol-7-monoacetate were limited by their poor water solubility. To address this issue, hydroxypropyl-ß-cyclodextrin (HP-ß-CD) complexes of the compounds were synthesized by the saturated aqueous method. The complexes were then analyzed using a differential scanning calorimeter. The IC50 of cheliensisin A was reduced by 45% and 58% against SW1116 and SMMC-7721 cell lines, respectively. Similarly, the IC50 of goniodiol-7-monoacetate was reduced by 55% and 34% against the two tumor cell lines, respectively. To further evaluate whether the styryllactones and complexes possessed selectivity against cancer cell lines and normal cell lines, toxicity against human normal cell line (HEK293T) was evaluated. The results demonstrated that the HP-ß-CD complexes displayed more cytotoxicity than the respective pristine compounds against the HEK293T cell line. However, there existed a therapeutic window when the complexes were applied against cancer cell lines. In summary, the synthesis of several styryllactone compounds complexed with HP-ß-CD was reported for the first time. These complexes could significantly enhance the cytotoxic effects of styryllactone compounds.

Isovalerylshikonin, a new resistance-modifying agent from Arnebia euchroma, supresses antimicrobial resistance of drug-resistant Staphylococcus aureus.

Antimicrobial resistance is the greatest threat to the treatment of bacterial infectious diseases. The development of resistance-modifying agents (RMAs) represents a promising strategy to mitigate the spread of bacterial antimicrobial resistance. In this study, a natural product, isovalerylshikonin (IVS), was isolated from Arnebia euchroma, a traditional Chinese medicine herb, that exhibited marginal antibacterial activity against drug-resistant Staphylococcus aureus RN4220, with a minimum inhibitory concentration (MIC) of 16 mg/L. In addition, a synergistic effect between IVS and streptomycin (STM) was detected by the microdilution antimicrobial chequerboard assay, with a reduction in the MIC of STM by up to 16-fold against strain RN4220. A bacterial ethidium bromide efflux assay and reverse transcription PCR were performed to investigate the synergistic mechanism. IVS significantly inhibited bacterial efflux and expression of msrA mRNA in vitro. A murine peritonitis/sepsis model was employed to test the in vivo synergistic activity of IVS and STM. IVS synergistically decreased bacterial counts with STM in peritoneal, spleen and liver tissue and increased mouse survival with STM in 7 days. The acute toxicity of IVS was tested and the 50% lethal dose (LD50) of IVS with a single exposure was 2.584 g/kg in mice. Overall, IVS, a low-toxicity RMA, exhibited synergistic antibacterial activities in vitro and in vivo against drug-resistant S. aureus. The effects were mediated by suppression of msrA mRNA expression and reduced bacterial efflux. In addition, these data support that IVS is a potential RMA against microbial resistance caused by the MsrA efflux pump.

Quantitative analysis of the cyclic peptide GG-8-6 in rat plasma using LC-MS/MS and its application to a pharmacokinetic study.

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related death worldwide. The discovery of new anticancer compounds is of great significance. GG-8-6, cyclo-(Val1-Leu2-Pro3-Ile4-Leu5-Leu6-Leu7-Val8-Leu9), a new synthetic cyclic peptide, might be a potential candidate for developing new anti-HCC drugs. GG-8-6 shares no structural homology to current anti-HCC drugs. Therefore, it was necessary to develop a quantitative method for the determination of GG-8-6 in vivo. Herein, a simple, specific and sensitive liquid chromatographic method with tandem mass spectrometric detection (LC-MS/MS) was developed and validated for the analysis of GG-8-6 in rat plasma. GG-8-6 and the internal standard (IS), A6, cyclo-(Val1-Leu2-Pro3-Ala4-Leu5-Leu6-Leu7-Val8-Leu9), were extracted from rat plasma by ethyl acetate. Chromatographic separation was performed on an Agilent Eclipse XDB-C18 column (4.6 × 150 mm, 5 µm) with a mobile phase consisting of acetonitrile-water containing 0.1% formic acid (90:10, v/v) with isocratic elution at a flow rate of 0.5 mL/min for 8.0 min. Multiple reaction monitoring (MRM) mode was performed with ion pairs of m/z: 974.8 → 861.8 for GG-8-6 and 932.7 → 819.8 for A6. The selectivity, matrix effects, recovery, intra- and inter-day precision and accuracy were validated with acceptable results in accordance with the US Food and Drug Administration guidelines. The calibration curve was linear (r2 > 0.99) over a concentration range of 1-1000 ng/mL with a lower limit of quantification (LLOQ) of 1 ng/mL. The method was successfully applied to the pharmacokinetic study of GG-8-6 in rats.

Synthesis and biological evaluation of cyclopeptide GG-8-6 and its analogues as anti-hepatocellular carcinoma agents.

GG-8-6, cyclo-(Val-Leu-Pro-Ile-Leu-Leu-Leu-Val-Leu, compound 1), and its twelve analogues (compound 2-13) were synthesized based on the lead compound Grifficyclocin B, a cyclic peptide with anti-tumor activity which was isolated from the plants of Goniothalamus species (Annonaceae). The bioassay results showed that these synthetic cyclopeptides exhibited different extent of cytotoxicity against human hepatocellular carcinoma cell lines. Among them, GG-8-6 (1) was the most active compound with IC50 values of 6.38 µM and 12.22 µM against SMMC-7721 and HepG2, respectively. Further studies on the mechanism demonstrated that GG-8-6 (1) could induce apoptosis and G2/M arrest of HCC cells, and the activation of caspase pathways was probably involved. In vivo anti-tumor experiments showed that GG-8-6 (1) could significantly inhibit the growth of tumor in the mouse xenograft tumor model. At the dose of 40 mg/kg, the inhibition ratio was 67.9% without weight loss. Our results suggested that GG-8-6 (1), a new cyclic peptide, might be a potential candidate for developing new anti-HCC drug in the coming future.