A facile synthesis of emodin derivatives, emodin carbaldehyde, citreorosein, and their 10-deoxygenated derivatives and their inhibitory activities on μ-calpain

Antibacterial activities of anthraquinones: structure-activity relationships and action mechanisms

With the increasing prevalence of untreatable infections caused by antibiotic-resistant bacteria, the discovery of new drugs from natural products has become a hot research topic. The antibacterial activity of anthraquinones widely distributed in traditional Chinese medicine has attracted much attention. Herein, the structure and activity relationships (SARs) of anthraquinones as bacteriostatic agents are reviewed and elucidated. The substituents of anthraquinone and its derivatives are closely related to their antibacterial activities. The stronger the polarity of anthraquinone substituents is, the more potent the antibacterial effects appear. The presence of hydroxyl groups is not necessary for the antibacterial activity of hydroxyanthraquinone derivatives. Substitution of di-isopentenyl groups can improve the antibacterial activity of anthraquinone derivatives. The rigid plane structure of anthraquinone lowers its water solubility and results in the reduced activity. Meanwhile, the antibacterial mechanisms of anthraquinone and its analogs are explored, mainly including biofilm formation inhibition, destruction of the cell wall, endotoxin inhibition, inhibition of nucleic acid and protein synthesis, and blockage of energy metabolism and other substances.

New dimeric chromanone derivatives from the mutant strains of Penicillium oxalicum and their bioactivities

Three new chromanone dimer derivatives, paecilins F-H (1-3) and ten known compounds (4-13), were obtained from the mutant strains of Penicillium oxalicum 114-2. Their structures were elucidated by extensive analysis of spectroscopic data and comparison with reported data, and the configurations of 1-3 were resolved by quantum chemical calculations of NMR shifts and ECD spectra. Compounds 5 and 11 showed significant anti-influenza A virus activities with IC50 values of 5.6 and 6.9 μM, respectively. Compounds 8 and 9 displayed cytotoxic activities against the MIA-PaCa-2 cell line with IC50 values of 2.6 and 2.1 μM, respectively. Compound 10 exhibited antibacterial activities against Bacillus cereus with a MIC value of 4 μg mL-1.

Drug Leads from Endophytic Fungi: Lessons Learned via Scaled Production

Recently, the isolation and elucidation of a series of polyhydroxyanthraquinones were reported from an organic extract of a solid phase culture of an endophytic fungus, Penicillium restrictum (strain G85). One of these compounds, ω-hydroxyemodin (1: ), showed promising quorum-sensing inhibition against clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) in both in vitro and in vivo models. The initial supply of 1: was 19 mg, and this amount needed to be scaled by a factor of 30 to 50 times, in order to generate material for further in vivo studies. To do so, improvements were implemented to enhance both the fermentation of the fungal culture and the isolation of this compound, with the target of generating > 800 mg of study materials in a period of 13 wk. Valuable insights, both regarding chemistry and mycology, were gained during the targeted production of 1: on the laboratory-scale. In addition, methods were modified to make the process more environmentally friendly by judicious choice of solvents, implementing procedures for solvent recycling, and minimizing the use of halogenated solvents.

Acute toxicity screening of different extractions, components and constituents of Polygonum multiflorum Thunb. on zebrafish (Danio rerio) embryos in vivo

Polygonum multiflorum Thunb. has been used widely in East Asia in treatment of diseases associated with aging. However, there are many reports referred to the toxicity of P. multiflorum, especially for liver adverse reactions. The toxicity of it is caused by over dosage or by the herb itself remains unclear. The aim of this study was to study the toxicity of different extractions, components and constituents of P. multiflorum, which were assessed in zebrafish embryos. Firstly, the difference of extracting solvent to the toxicity of P. multiflorum was researched to probe the influence of usages to the safety of P. multiflorum. The toxicity of 70% EtOH extract is considerably higher than that of other extracts. Secondly, 70% EtOH extract was subjected to macroporous resin (DM-8) eluting with a gradient of water and EtOH (H₂O, 25% EtOH, 40% EtOH and 95% EtOH) to give four components (A-D). The toxicity of the component (D) showed higher than the other components (A-C). Thus, the component (D) was taken more attentions to research. Lastly, study on the chemical constituents of the component (D), 27 compounds, including 7 anthraquinones (1-7), 8 stilbenes (8-15), 7 anthrones (16-22), 3 cinnamic acid amides (23-25), 2 naphthols (26-27) were isolated and assessed in zebrafish embryos. Compounds 1-3, 16-22 and 26-27 showed severe toxicity against the zebrafish embryos while other compounds, such as stilbenes, showed no obvious toxicity.

Design and synthesis of emodin derivatives as novel inhibitors of ATP-citrate lyase

Aberrant cellular metabolism drives cancer proliferation and metastasis. ATP citrate lyase (ACL) plays a critical role in generating cytosolic acetyl CoA, a key building block for de novo fatty acid and cholesterol biosynthesis. ACL is overexpressed in cancer cells, and siRNA knockdown of ACL limits cancer cell proliferation and reduces cancer stemness. We characterized a new class of ACL inhibitors bearing the key structural feature of the natural product emodin. Structure-activity relationship (SAR) study led to the identification of 1d as a potent lead that demonstrated dose-dependent inhibition of proliferation and cancer stemness of the A549 lung cancer cell line. Computational modeling indicates this class of inhibitors occupies an allosteric binding site and blocks the entrance of the substrate citrate to its binding site.

Hypericin: chemical synthesis and biosynthesis

Hypericin is one of the most important phenanthoperylene quinones extracted mainly from plants of the genus Hypericum belonging to the sections Euhypericum and Campylosporus of Keller's classification. Widespread attention to the antiviral and anti-tumor properties of hypericin has spurred investigations of the chemical synthesis and biosynthesis of this unique compound. However, the synthetic strategies are challenging for organic and biological chemists. In this review, specific significant advances in total synthesis, semi-synthesis, and biosynthesis in the past decades are summarized.