Synthesis and Antiproliferative Activity Evaluation of the Disulfide-Containing Cyclic Peptide Thiochondrilline C and Derivatives

Natural Products from Actinobacteria as a Potential Source of New Therapies Against Colorectal Cancer: A Review

Colorectal cancer (CRC) is a common, and deadly disease. Despite the improved knowledge on CRC heterogeneity and advances in the medical sciences, there is still an urgent need to cope with the challenges and side effects of common treatments for the disease. Natural products (NPs) have always been of interest for the development of new medicines. Actinobacteria are known to be prolific producers of a wide range of bioactive NPs, and scientific evidence highlights their important protective role against CRC. This review is a holistic picture on actinobacter-derived cytotoxic compounds against CRC that provides a good perspective for drug development and design in near future. This review also describes the chemical structure of 232 NPs presenting anti-CRC activity with the being majority of quinones, lactones, alkaloids, peptides, and glycosides. The study reveals that most of these NPs are derived from marine actinobacteria followed by terrestrial and endophytic actinobacteria, respectively. They are predominantly produced by Streptomyces, Micromonospors, Saliniospors and Actinomadura, respectively, in which Streptomyces, as the predominant contributor generating over 76% of compounds exclusively. Besides it provides a valuable snapshot of the chemical structure-activity relationship of compounds, highlighting the presence or absence of some specific atoms and chemical units in the structure of compounds can greatly influence their biological activities. To the best of our knowledge, this is the first comprehensive review on natural actinobacterial compounds affecting different types of CRC. Our study reveals that the high diversity of actinobacterial strains and their NPs derivatives, described here provides a new perspective and direction for the production of new anti-CRC drugs and paves the way to innovation for drugs discovery in the future. The knowledge obtain from this review can help us to understand the pivotal application of actinobacteria in future drugs development.

Thiocoraline mediates drug resistance in MCF-7 cells via PI3K/Akt/BCRP signaling pathway

Thiocoraline, a depsipeptide bisintercalator with potent antitumor activity, was first isolated from marine actinomycete Micromonospora marina. It possesses an intense toxicity to MCF-7 cells at nanomolar concentrations in a dose-dependent manner evaluated by MTT assay and crystal violet staining. We established a human breast thiocoraline-resistant cancer subline of MCF-7/thiocoraline (MCF-7/T) to investigate the expression variation of breast cancer resistance proteins (BCRP) and its subsequent influence on drug resistance. Colony-forming assay showed that the MCF-7 cells proliferated faster than the MCF-7/T cells in vitro. Western blot analysis demonstrated that thiocoraline increased the phosphorylation of Akt. Additionally, the sensitivity of tumor cells to thiocoraline was reduced with a concurrent rise in phosphorylation level of Akt and of BCRP expression.These studies indicated that thiocoraline probably mediated the drug resistance via PI3K/Akt/BCRP signaling pathway. MK-2206 dihydrochloride, a selective phosphorylation inhibitor of Akt, significantly decreased MCF-7 cell viability under exposure to thiocoraline compared to the control. However, it was not obviously able to decrease MCF-7/T cell viability when cells were exposed to thiocoraline.

Recent Advances in the Synthesis of Peptoid Macrocycles

Over the past two decades, developing medical applications for peptides has, and continues to be a highly active area of research. At present there are over 60 peptide-based drugs on the market and more than 140 in various stages of clinical trials. The interest in peptide-based therapeutics arises from their biocompatibility and their ability to form defined secondary and tertiary structures, resulting in a high selectivity for complex targets. However, there are significant challenges associated with the development of peptide-based therapeutics, namely peptides are readily metabolised in vivo. Peptoids are an emerging class of peptidomimetic and they offer an alternative to peptides. Peptoids are comprised of N-substituted glycines where side-chains are located on the nitrogen atom of the amide backbone rather than the α-carbon as is the case in peptides. This change in structure confers a high degree of resistance to proteolytic degradation but the absence of any backbone hydrogen bonding means that peptoids exhibit a high degree of conformational flexibility. Cyclisation has been explored as one possible route to rigidify peptoid structures, making them more selective, and, therefore more desirable as potential therapeutics. This review outlines the various strategies that have been developed over the last decade to access new types of macrocyclic peptoids.

Base-controlled Fe(Pc)-catalyzed aerobic oxidation of thiols for the synthesis of S–S and S–P(O) bonds

Base-controlled Fe(Pc)-catalyzed S–S/S–P(O) bond formation.

Marine natural products

Covering: 2015. Previous review: Nat. Prod. Rep., 2016, 33, 382-431This review covers the literature published in 2015 for marine natural products (MNPs), with 1220 citations (792 for the period January to December 2015) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1340 in 429 papers for 2015), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

Synthesis of quinolines via copper-catalyzed domino reactions of enaminones

Enaminones showcase synthetic utility for the synthesis of quinoline derivatives via copper-catalyzed domino reactions involving C–N bond formation, aldol reaction and dehydration.