New point of view about optical activity in a helically-coiled fiber

The optical activity in a helically-coiled optical fiber is reexamined. It is proven that not only is there no circular birefringence in the fiber but the polarization relative to the laboratory reference frame is not rotated along the fiber. The reason for this is that in contrast with the polarization vector, the Jones vector does not give a complete description of the polarization. As a mathematical entity in some local reference frame that depends on the instantaneous propagation direction, it can only describe the state of polarization relative to that reference frame. With the new implication of the Jones vector, the results of the experiment reported by Papp and Harms in 1977 are explained satisfactorily. In particular, it is shown that the state of polarization relative to the Tang frame remains unchanged along the fiber. The optical activity appears only relative to the Serret-Frenet frame

Physapubescin B Exhibits Potent Activity against Human Prostate Cancer In Vitro and In Vivo

The present data showed that a natural compound isolated from the plant <i>Physalis pubescens</i> L. (Solanaceae), physapubescin B, exhibited antitumor activity against prostate cancer in vitro and in vivo. Treating prostate cancer cells with physapubescin B resulted in the accumulation of cells in the G2/M phase, which was associated with reduced Cdc25C levels and increased levels of CyclinB1, P21 as well as p-Cdk1 (Tyr15). Additionally, reactive oxygen species (ROS) generation was increased in physapubescin B-treated PC-3 cells. Furthermore, the physapubescin B-induced decrease of Cdc25C protein expression together with the G2/M phase cell cycle arrest were significantly abrogated by antioxidant NAC and GSH. Our data also demonstrated that physapubescin B exhibited strong in vivo antitumor efficacy in human prostate cancer PC3 xenograft. In conclusion, our results provide clear evidence that physapubescin B exhibits antitumor activity both in vitro and in vivo and deserves further development as an anticancer agent

Angucycline antibiotics and its derivatives from marine-derived actinomycete <i>Streptomyces</i> sp. A6H

<p>Vineomycin A₁ (<b>1</b>) and B₂ (<b>2</b>) were isolated from the culture broth of marine actinomycete <i>Streptomyces</i> sp. A6H. Five hydrolysis products were obtained by rational hydrolysis and methanolysis of the fermentation extract. Their structures were characterised as aquayamycin (<b>3</b>), vineomycinone B₂ (<b>4</b>), 9-C-_D-olivosyltetrangulol (<b>5</b>), 7-O-methylgaltamycinone (<b>6</b>) and vineomycinone B₂ methyl ester (<b>7</b>). In addition to these compounds, two ester derivatives, vineolactone A (<b>8)</b> and vineomycinone B₂ benzyl ester (<b>9</b>) of compound <b>4</b> were generated semisynthetically. Compound <b>6</b> is a new analogue of galtamycinone, while compounds <b>8</b> and <b>9</b> are new members of vineomycins. Cytotoxic activities and antimicrobial activities were determined for all compounds. The results indicate that only compound <b>1</b> showed significant activities with IC₅₀ value of 0.34 μM against H1975 and MIC value of 4 μg/mL against <i>Staphylococcus aureus.</i></p

Engineered Biosynthesis and Anticancer Studies of Ring-Expanded Antimycin-Type Depsipeptides

Respirantins are 18-membered antimycin-type depsipeptides produced by Streptomyces sp. and Kitasatospora sp. These compounds have shown extraordinary anticancer activities against a panel of cancer cell lines with nanomolar levels of IC50 values. However, further investigation has been impeded by the low titers of the natural producers and the challenging chemical synthesis due to their structural complexity. The biosynthetic gene cluster (BGC) of respirantin was previously proposed based on a bioinformatic comparison of the four members of antimycin-type depsipeptides. In this study, we report the first successful reconstitution of respirantin in Streptomyces albus using a synthetic BGC. This heterologous system serves as an accessible platform for the production and diversification of respirantins. Through polyketide synthase pathway engineering, biocatalysis, and chemical derivatization, we generated nine respirantin compounds, including six new derivatives. Cytotoxicity screening against human MCF-7 and Hela cancer cell lines revealed a unique biphasic dose–response profile of respirantin. Furthermore, a structure–activity relationship study has elucidated the essential functional groups that contribute to its remarkable cytotoxicity. This work paves the way for respirantin-based anticancer drug discovery and development