Synthesis and evaluation of Na+/K+-ATP-ase inhibiting and cytotoxic in vitro activities of oleandrigenin and its selected 17β-(butenolidyl)- and 17β-(3-furyl)- analogues

Discovery of Novel 3,11-Bispeptide Ester Arenobufagin Derivatives with Potential in Vivo Antitumor Activity and Reduced Cardiotoxicity

Arenobufagin, one of the bufadienolides isolated from traditional Chinese medicine Chan'su, exhibits potent antitumor activity. However, serious toxicity and small therapeutic window limits its drug development. In the present study, to our knowledge, novel 3,11-bispeptide ester arenobufagin derivatives have been firstly designed and synthesized on the base of our previous discovery of active 3-monopeptide ester derivative. The in vitro antiproliferative activity evaluation revealed that the moiety at C3 and C11 hydroxy had an important influence on cytotoxic activity and selectivity. Compound ZM350 notably inhibited tumor growth by 58.8 % at a dose 10 mg/kg in an A549 nude mice xenograft model. Therefore, compound ZM350 also presented a concentration-dependent apoptosis induction and low inhibitory effect against both hERG potassium channel and Cav1.2 calcium channel. Our study suggests that novel 3,11-bispeptide ester derivatives will be a potential benefit to further antitumor agent development of arenobufagin.

Biological evaluation of antiproliferative and anti-invasive properties of an androstadiene derivative on human cervical cancer cell lines

Gynaecological cancers are leading cause of death: breast cancer is the most frequently diagnosed type of malignancies, and cervical neoplasms rank fourth for both incidence and mortality among women worldwide. In one of our previous studies, favourable antiproliferative and antimetastatic properties of a newly synthesized androstane derivative, 17APAD have been demonstrated on breast cancer cell lines with different expression patterns of hormone receptors. The aim of the current study was to investigate the antitumoral potential of this molecule in cervical cancer cell lines, including SiHa cells positive for human papilloma virus (HPV) type 16 and HPV-negative C33A cells. 17APAD exerted pronounced growth-inhibition (with IC₅₀ values ranging from 0.76 to 1.72 μM with considerable cancer selectivity), while cisplatin used as a reference agent yielded higher IC₅₀ values (ranging from 3.69 to 12.43) and less selectivity, as evidenced by MTT assay. The proapoptotic effect and morphological changes induced by 17APAD were detected by Hoechst 33258-propidium iodide or Annexin V-Alexa488-propidium iodide fluorescent double staining methods, supplemented with a caspase-3 activity assay to identify the mechanism behind the programmed cell death induced by 17APAD. Additionally, significant and concentration-dependent elevation of the ratio of cells in the G2/M phase, on the expense of G0/G1 phase, was observed after 48 h of exposure to 17APAD. Besides its potent antiproliferative properties against both cervical cancer cell lines, 17APAD elicited a remarkable inhibition of cell migration and invasion as detected in wound-healing and Boyden chamber assays, respectively. The mechanisms of action underlying the effects of 17APAD on cell proliferation and motility were independent of androgenic activity, as demonstrated by the Yeast Androgen Screen method. Our results provide new evidence for the proapoptotic and anti-invasive properties of 17APAD, suggesting that it is worth of further research, as a promising prototype for designing novel anticancer agents.

Synthesis of Cardiotonic Steroids Oleandrigenin and Rhodexin B

This article describes a concise synthesis of cardiotonic steroids oleandrigenin (7) and its subsequent elaboration into the natural product rhodexin B (2) from the readily available intermediate (8) that could be derived from the commercially available steroids testosterone or DHEA via three-step sequences. These studies feature an expedient installation of the β16-oxidation based on β14-hydroxyl-directed epoxidation and subsequent epoxide rearrangement. The following singlet oxygen oxidation of the C17 furan moiety provides access to oleandrigenin (7) in 12 steps (LLS) and a 3.1% overall yield from 8. The synthetic oleandrigenin (7) was successfully glycosylated with l-rhamnopyranoside-based donor 28 using a Pd(II)-catalyst, and the subsequent deprotection under acidic conditions provided cytotoxic natural product rhodexin B (2) in a 66% yield (two steps).

Cardiac Glycosides as Immune System Modulators

Cardiac glycosides (CGs) are natural steroid compounds occurring both in plants and animals. They are known for long as cardiotonic agents commonly used for various cardiac diseases due to inhibition of Na⁺/K⁺-ATPase (NKA) pumping activity and modulating heart muscle contractility. However, recent studies show that the portfolio of diseases potentially treatable with CGs is much broader. Currently, CGs are mostly studied as anticancer agents. Their antiproliferative properties are based on the induction of multiple signaling pathways in an NKA signalosome complex. In addition, they are strongly connected to immunogenic cell death, a complex mechanism of induction of anticancer immune response. Moreover, CGs exert various immunomodulatory effects, the foremost of which are connected with suppressing the activity of T-helper cells or modulating transcription of many immune response genes by inhibiting nuclear factor kappa B. The resulting modulations of cytokine and chemokine levels and changes in immune cell ratios could be potentially useful in treating sundry autoimmune and inflammatory diseases. This review aims to summarize current knowledge in the field of immunomodulatory properties of CGs and emphasize the large area of potential clinical use of these compounds.

Total Synthesis of the Cardiotonic Steroid (+)-Cannogenol

The total synthesis of (+)-cannogenol, an aglycon common to various biologically important cardiotonic glycosides, has been achieved. Synthesis of the versatile intermediate involves Mizoroki-Heck and intramolecular Diels-Alder reactions from the enantiomerically pure CD-ring segment, newly prepared in a multidecagram scale this time. Total synthesis by the site-selective transformations of the versatile intermediate demonstrated the applicability of our synthetic approach.