Preparation of Indolin-3-one-Containing 1,4-Naphthoquinone Derivatives via Organocatalytic Asymmetric Michael Addition Reaction.

This article explores the asymmetric Michael addition reaction of 2-hydroxy-1,4-naphthoquinone and indole-3-ones catalyzed by cinchona alkaloids. This strategy utilizes 2-hydroxy-1,4-naphthoquinone and easily prepared indole-3-one as substrates, resulting in the synthesis of 23 unprecedented indolin-3-ones bearing a 1,4-naphthoquinone unit at the C2 position of indole under simple and mild reaction conditions, with up to 88% yield, 98% ee, and >20:1 dr.

Design, synthesis and biological evaluation of indole-2-carboxylic acid derivatives as novel HIV-1 integrase strand transfer inhibitors.

Integrase plays an important role in the life cycle of HIV-1, and integrase strand transfer inhibitors (INSTIs) can effectively impair the viral replication. However, drug resistance mutations have been confirmed to decrease the efficacy of INSTI during the antiviral therapy. Herein, indole-2-carboxylic acid (1) was found to inhibit the strand transfer of integrase, and the indole nucleus of compound 1 was observed to chelate with two Mg2+ ions within the active site of integrase. Through optimization of compound 1, a series of indole-2-carboxylic acid derivatives were designed and synthesized, and compound 17a was proved to markedly inhibit the effect of integrase, with IC50 value of 3.11 µM. Binding mode analysis of 17a demonstrated that the introduced C6 halogenated benzene ring could effectively bind with the viral DNA (dC20) through π-π stacking interaction. These results indicated that indole-2-carboxylic acid is a promising scaffold for the development of integrase inhibitors.

Rh(III)-Catalyzed C7-Alkylation of Isatogens with Malonic Acid Diazoesters.

Rh(III)-catalyzed C7-alkylation of isatogens (indolin-3-one N-oxides) with malonic acid diazoesters has been developed. This strategy utilizes oxygen anion on the N-oxide group of isatogens as a directing group and successfully achieves the synthesis of a series of C7-alkylated isatogens with moderate to good yields (48-86% yields). Moreover, the N-oxides of isatogens can not only serve as the simple directing group for C7-H bond cleavage but also be deoxidized for easy removal.

The Discovery of Indole-2-carboxylic Acid Derivatives as Novel HIV-1 Integrase Strand Transfer Inhibitors.

As an important antiviral target, HIV-1 integrase plays a key role in the viral life cycle, and five integrase strand transfer inhibitors (INSTIs) have been approved for the treatment of HIV-1 infections so far. However, similar to other clinically used antiviral drugs, resistance-causing mutations have appeared, which have impaired the efficacy of INSTIs. In the current study, to identify novel integrase inhibitors, a set of molecular docking-based virtual screenings were performed, and indole-2-carboxylic acid was developed as a potent INSTI scaffold. Indole-2-carboxylic acid derivative 3 was proved to effectively inhibit the strand transfer of HIV-1 integrase, and binding conformation analysis showed that the indole core and C2 carboxyl group obviously chelated the two Mg2+ ions within the active site of integrase. Further structural optimizations on compound 3 provided the derivative 20a, which markedly increased the integrase inhibitory effect, with an IC50 value of 0.13 µM. Binding mode analysis revealed that the introduction of a long branch on C3 of the indole core improved the interaction with the hydrophobic cavity near the active site of integrase, indicating that indole-2-carboxylic acid is a promising scaffold for the development of integrase inhibitors.

Synthesis of diarylmethyl thioethers via a DABCO-catalyzed 1,6-conjugate addition reaction of p-quinone methides with organosulfur reagents.

A rapid and simple method was developed for the synthesis of diarylmethyl thioethers via a DABCO-catalyzed 1,6-conjugate addition reaction of para-quinone methides (p-QMs) with organosulfur reagents. A series of diarylmethyl thioethers were synthesized at 13-85% yields by this method. After that, the antibacterial activities of synthesized diarylmethyl thioethers and their derivatives were evaluated. The MIC range (µg mL-1) against Staphylococcus aureus ATCC 25923 and clinically isolated methicillin-resistant S. aureus was 8-128 and 64-128, respectively.

Effects of a Nanonetwork-Structured Soil Conditioner on Microbial Community Structure.

Fertilizer application can increase yields, but nutrient runoff may cause environmental pollution and affect soil quality. A network-structured nanocomposite used as a soil conditioner is beneficial to crops and soil. However, the relationship between the soil conditioner and soil microbes is unclear. We evaluated the soil conditioner's impact on nutrient loss, pepper growth, soil improvement, and, especially, microbial community structure. High-throughput sequencing was applied to study the microbial communities. The microbial community structures of the soil conditioner treatment and the CK were significantly different, including in diversity and richness. The predominant bacterial phyla were Pseudomonadota, Actinomycetota, and Bacteroidota. Acidobacteriota and Chloroflexi were found in significantly higher numbers in the soil conditioner treatment. Ascomycota was the dominant fungal phylum. The Mortierellomycota phylum was found in significantly lower numbers in the CK. The bacteria and fungi at the genus level were positively correlated with the available K, available N, and pH, but were negatively correlated with the available P. Our results showed that the loss of nutrients controlled by the soil conditioner increased available N, which improved soil properties. Therefore, the microorganisms in the improved soil were changed. This study provides a correlation between improvements in microorganisms and the network-structured soil conditioner, which can promote plant growth and soil improvement.

Design, synthesis and biological evaluation of new multi-target scutellarein hybrids for treatment of Alzheimer's disease.

Scutellarein hybrids were designed, synthesized and evaluated as multifunctional therapeutic agents for the treatment of Alzheimer's disease (AD). Compounds 11a-i, containing a 2-hydroxymethyl-3,5,6-trimethylpyrazine fragment at the 7-position of scutellarein, were found to have balanced and effective multi-target potencies against AD. Among them, compound 11e exhibited the most potent inhibition of electric eel and human acetylcholinesterase enzymes with IC50 values of 6.72 ± 0.09 and 8.91 ± 0.08 µM, respectively. In addition, compound 11e displayed not only excellent inhibition of self- and Cu2+-induced Aß1-42 aggregation (91.85% and 85.62%, respectively) but also induced disassembly of self- and Cu2+-induced Aß fibrils (84.54% and 83.49% disaggregation, respectively). Moreover, 11e significantly reduced tau protein hyperphosphorylation induced by Aß25-35, and also exhibited good inhibition of platelet aggregation. A neuroprotective assay demonstrated that pre-treatment of PC12 cells with 11e significantly decreased lactate dehydrogenase levels, increased cell viability, enhanced expression of relevant apoptotic proteins (Bcl-2, Bax and caspase-3) and inhibited RSL3-induced PC12 cell ferroptosis. Furthermore, hCMEC/D3 and hPepT1-MDCK cell line permeability assays indicated that 11e would have optimal blood-brain barrier and intestinal absorption characteristics. In addition, in vivo studies revealed that compound 11e significantly attenuated learning and memory impairment in an AD mice model. Toxicity experiments with the compound did not reveal any safety concerns. Notably, 11e significantly reduced ß-amyloid precursor protein (APP) and ß-site APP cleaving enzyme-1 (BACE-1) protein expression in brain tissue of scopolamine-treated mice. Taken together, these outstanding properties qualified compound 11e as a promising multi-target candidate for AD therapy, worthy of further studies.

Protecting-Group-Free Synthesis of Meridianin A-G and Derivatives and Its Antibiofilm Evaluation.

Herein, a protecting-group-free protocol was developed to realize a time and step economy diversification of the Meridianin alkaloid. A broad range of substituents are tolerated to deliver the products in moderate to high yields, and the first synthesis of Meridianin B was achieved. The simplicity of this protocol enables the rapid construction of a Meridianin derivative library for antibiofilm evaluation. Preliminary results reveal that Meridianin derivatives were capable of inhibiting the Acinetobacter baumannii biofilm and lowering the antibiotic MIC synergistically.

DBU-Catalyzed Aerobic CDC Reaction of Thiophenols.

A convenient method was developed for the preparation of thiolated compounds via a DBU-catalyzed aerobic cross-dehydrogenative coupling (CDC) reaction. The established protocol is environmentally friendly and operationally simple. Substrates like (hetero)aryl acetates, (hetero)aryl ketones, and indoles could be transformed into the corresponding thiolated products in moderate to high yields and further applied in the preparation of bioactive compounds in a prefunctionalization-free manner.

Synthesis and antibiofilm evaluation of N-acyl-2-aminopyrimidine derivatives against Acinetobacter baumannii.

The overuse of antibiotics will led to the increase of drug resistance. Especially, the multidrug-resistant A. baumannii became the leading cause of nosocomial infections with high rates of morbimortality. The drug resistance of A. baumannii is greatly attributed to its biofilm. To alleviate the burden of drug resistance, the anti-virulence signaling strategies was developed. By specifically interfering with the ability of the bacteria to recognize host signals that are needed to establish infection, the bacteria are less able to colonize the host. In this paper, 39 N-acyl-2-aminopyrimidine derivatives were synthesized and tested for their biofilm inhibition efficacy. The screening results reveal that some of the analogues (3ac, 8d) efficiently inhibited the biofilm formation of A. baumannii (IC50 as low as 3.8 µM), and the biofilm inhibition ability was further demonstrated with laser confocal results and extracellular polysaccharides inhibition test. Further motility test reveals our compounds are quorum sensing inhibitors. Besides, the synergistic effect of compounds 3ac and 8d with different antibiotics suggest its potential clinical significance, which was further enhanced by the long time biofilm inhibition test after coating with PLGA. Finally, we also look into the safety of the compounds with cytotoxicity assay.

Synthesis and antibacterial activity studies in vitro of indirubin-3'-monoximes.

Multi-drug-resistant microbial pathogens are a serious global health problem. New compounds with antibacterial activity serve as good candidates for developing novel antibacterial drugs which is very urgent and important. In this work, based on the unique scaffold of indirubin, an active ingredient of traditional Chinese medicine formulation Danggui Luhui Wan, we synthesized 29 indirubin-3'-monoximes and preliminarily evaluated their antibacterial activities. The antibacterial activity results demonstrated that the synthesized indirubin-3'-monoximes 5a-5z and 5aa-5ad displayed good potency against S. aureus ATCC25923 (MIC = 0.4-25.6 µg mL-1). Among them, we found that the 5-F, 5-Cl and 7-CF3 substituted indirubin-3'-monoximes 5r, 5s and 5aa also showed better antibacterial efficiency for S. aureus (MICs up to 0.4 µg mL-1) than the prototype natural product indirubin (MIC = 32 µg mL-1). More importantly, indirubin-3'-monoxime 5aa has certain synergistic effect with levofloxacin against clinic multidrug-resistant S. aureus (fractional inhibitory concentration index: 0.375). In addition, relevant experiments including electron microscopy observations, PI staining and the leakage of extracellular potassium ions and nucleic acid (260 nm) have been performed after treating S. aureus with indirubin-3'-monoxime 5aa, and the results revealed that indirubin-3'-monoximes could increase the cell membrane permeability of S. aureus. Although indirubin-3'-monoxime 5aa showed some cytotoxicity toward SH-SY5Y cells relative to compounds 5r and 5s, the skin irritation test of male mice after shaving showed that compound 5aa at a concentration of 12.8 µg mL-1 had no toxicity to mouse skin, and it could be used as a leading compound for skin antibacterial drugs.

Transcriptome Analysis of Tryptophan-Induced Resistance against Potato Common Scab.

Potato common scab (CS) is a worldwide soil-borne disease that severely reduces tuber quality and market value. We observed that foliar application of tryptophan (Trp) could induce resistance against CS. However, the mechanism of Trp as an inducer to trigger host immune responses is still unclear. To facilitate dissecting the molecular mechanisms, the transcriptome of foliar application of Trp and water (control, C) was compared under Streptomyces scabies (S) inoculation and uninoculation. Results showed that 4867 differentially expressed genes (DEGs) were identified under S. scabies uninoculation (C-vs-Trp) and 2069 DEGs were identified under S. scabies inoculation (S-vs-S+Trp). Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses indicated that Trp induced resistance related to the metabolic process, response to stimulus, and biological regulation. As phytohormone metabolic pathways related to inducing resistance, the expression patterns of candidate genes involved in salicylic acid (SA) and jasmonic acid/ethylene (JA/ET) pathways were analyzed using qRT-PCR. Their expression patterns showed that the systemic acquired resistance (SAR) and induced systemic resistance (ISR) pathways could be co-induced by Trp under S. scabies uninoculation. However, the SAR pathway was induced by Trp under S. scabies inoculation. This study will provide insights into Trp-induced resistance mechanisms of potato for controlling CS, and extend the application methods of Trp as a plant resistance inducer in a way that is cheap, safe, and environmentally friendly.

Role of no table salt on hypertension and stroke based on large sample size from National Health and Nutrition Examination Survey database.

BACKGROUND: To assess the associations between no table salt and hypertension or stroke. METHODS: The data of 15,352 subjects were collected from National Health and Nutrition Examination Survey (NHANES) database. All subjects were divided into no hypertension or stroke group (n = 10,894), hypertension group (n = 5888), stroke group (n = 164) and hypertension and stroke group (n = 511). Univariate and multivariate logistic regression analysis was used to measure the associations of salt type used with hypertension and stroke and co-variables were respectively adjusted in different models. RESULTS: After adjusting age and gender, other salt intake was associated with 1.88-fold risk of hypertension (OR = 1.88, 95%CI: 1.44-2.46) and no table salt was associated with 1.30-fold risk of hypertension (OR = 1.30, 95%CI: 1.15-1.47). After adjusting age, gender, race, BMI, PIR, marital status, CVDs, whether doctors' told them to reduce salt, and diabetes, the risk of hypertension was 1.23-fold increase in no table salt group (OR = 1.23, 95%CI: 1.04-1.46). After the adjustment of age and gender, the risk of hypertension and stroke was 3.33-fold increase (OR = 3.33, 95%CI: 2.12-5.32) in other salt intake group and 1.43-fold increase (OR = 1.43, 95%CI:1.17-1.74) in no table salt group. CONCLUSION: Other salt intake or no table salt were associated with a higher risk of hypertension or hypertension and stroke.

Design, Synthesis, and Biological Evaluation of N14-Amino Acid-Substituted Tetrandrine Derivatives as Potential Antitumor Agents against Human Colorectal Cancer.

As a typical dibenzylisoquinoline alkaloid, tetrandrine (TET) is clinically used for the treatment of silicosis, inflammatory pulmonary, and cardiovascular diseases in China. Recent investigations have demonstrated the outstanding anticancer activity of this structure, but its poor aqueous solubility severely restricts its further development. Herein, a series of its 14-N-amino acid-substituted derivatives with improved anticancer effects and aqueous solubility were designed and synthesized. Among them, compound 16 displayed the best antiproliferative activity against human colorectal cancer (HCT-15) cells, with an IC50 value of 0.57 µM. Compared with TET, 16 was markedly improved in terms of aqueous solubility (by 5-fold). Compound 16 significantly suppressed the colony formation, migration, and invasion of HCT-15 cells in a concentration-dependent manner, with it being more potent in this respect than TET. Additionally, compound 16 markedly impaired the morphology and motility of HCT-15 cells and induced the death of colorectal cancer cells in double-staining and flow cytometry assays. Western blot results revealed that 16 could induce the autophagy of HCT-15 cells by significantly decreasing the content of p62/SQSTM1 and enhancing the Beclin-1 level and the ratio of LC3-II to LC3-I. Further study showed that 16 effectively inhibited the proliferation, migration, and tube formation of umbilical vein endothelial cells, manifesting in a potent anti-angiogenesis effect. Overall, these results revealed the potential of 16 as a promising candidate for further preclinical studies.

A solid-supported organocatalyst for asymmetric Mannich reaction to construct C2-quaternary indolin-3-ones.

A simple and novel solid-supported organocatalyst from a 2-chlorotrityl chloride resin-immobilized 4-hydroxyproline was developed, and this organocatalyst has been used for the asymmetric Mannich reaction of 2-aryl-3H-indol-3-ones and aldehydes/ketones. A series of C2-quaternary indolin-3-ones were prepared in good yields (up to 83%) and with excellent diastereoselectivities (up to 20 : 1) and enantioselectivities (up to 99% ee). In addition, the organocatalyst can be recovered by simple filtration and also be reused for the asymmetric Mannich reaction without significant loss of catalytic efficiency.

Design, synthesis and evaluation of novel scutellarin and scutellarein-N,N-bis-substituted carbamate-l-amino acid derivatives as potential multifunctional therapeutics for Alzheimer's disease.

In this study, we designed, synthesized and evaluated a series of scutellarin and scutellarein-N,N-bis-substituted carbamate-l-amino acid derivatives as multifunctional therapeutic agents for the treatment of Alzheimer's disease (AD). Compounds containing scutellarein as the parent nucleus (6a-l) had good inhibitory activity against acetyl cholinesterase (AChE), with compound 6 h exhibiting the most potent inhibition of electric eel AChE and human AChE enzymes with IC50 values of 6.01 ± 1.66 and 7.91 ± 0.49 µM, respectively. In addition, compound 6 h displayed not only excellent inhibition of self- and Cu2+-induced Aß1-42 aggregation (89.17% and 86.19% inhibition) but also induced disassembly of self- and Cu2+-induced Aß fibrils (84.25% and 78.73% disaggregation). Moreover, a neuroprotective assay demonstrated that pre-treatment of PC12 cells with 6 h significantly decreased lactate dehydrogenase levels, increased cell viability, enhanced expression of relevant apoptotic proteins (Bcl-2, Bax, and caspase-3) and inhibited RSL3 induced PC12 cell ferroptosis. Furthermore, hCMEC/D3 and hPepT1-MDCK cell line permeability assays indicated that 6 h would have optimal blood-brain barrier and intestinal absorption characteristics. The in vivo experimental data suggested that 6 h ameliorated learning and memory impairment in mice by decreasing AChE activity, increasing ACh levels and alleviating pathological damage of hippocampal tissue cells. These multifunctional properties highlight compound 6 h as a promising candidate for development as a multifunctional drug against AD.

Attenuation of NLRP3 Inflammasome Activation by Indirubin-Derived PROTAC Targeting HDAC6.

Histone deacetylase 6 (HDAC6) is a potential therapeutic target for treating several diseases. A recent study revealed that HDAC6 is important for NLRP3 inflammasome activation, suggesting that targeting HDAC6 could be useful for treating many inflammatory disorders. Using the proteolysis targeting chimera (PROTAC) strategy, we herein report an HDAC6 degrader with low cytotoxicity by tethering a selective HDAC6 inhibitor derived from a natural product, indirubin, with pomalidomide, a CRBN E3 ligand. Our HDAC6 degrader efficiently and selectively decreased HDAC6 levels in several cell lines, including activated THP-1 cells. Application of this HDAC6 degrader attenuated NLRP3 inflammasome activation in LPS-induced mice, which for the first time demonstrates that HDAC6 PROTAC could be a novel strategy to treat NLRP3 inflammasome-associated diseases.

iTRAQ-Based Proteomics Analysis of Response to Solanum tuberosum Leaves Treated with the Plant Phytotoxin Thaxtomin A.

Thaxtomin A (TA) is a phytotoxin secreted by Streptomyces scabies that causes common scab in potatoes. However, the mechanism of potato proteomic changes in response to TA is barely known. In this study, the proteomic changes in potato leaves treated with TA were determined using the Isobaric Tags for Relative and Absolute Quantitation (iTRAQ) technique. A total of 693 proteins were considered as differentially expressed proteins (DEPs) following a comparison of leaves treated with TA and sterile water (as a control). Among the identified DEPs, 460 and 233 were upregulated and downregulated, respectively. Based on Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, many DEPs were found to be involved in defense and stress responses. Most DEPs were grouped in carbohydrate metabolism, amino acid metabolism, energy metabolism, and secondary metabolism including oxidation-reduction process, response to stress, plant-pathogen interaction, and plant hormone signal transduction. In this study, we analyzed the changes in proteins to elucidate the mechanism of potato response to TA, and we provided a molecular basis to further study the interaction between plant and TA. These results also offer the option for potato breeding through analysis of the resistant common scab.

Indirubin Derivatives as Dual Inhibitors Targeting Cyclin-Dependent Kinase and Histone Deacetylase for Treating Cancer.

To utilize the unique scaffold of a natural product indirubin, we herein adopted the strategy of combined pharmacophores to design and synthesize a series of novel indirubin derivatives as dual inhibitors against cyclin-dependent kinase (CDK) and histone deacetylase (HDAC). Among them, the lead compound 8b with remarkable CDK2/4/6 and HDAC6 inhibitory activity of IC50 = 60.9 ± 2.9, 276 ± 22.3, 27.2 ± 4.2, and 128.6 ± 0.4 nM, respectively, can efficiently induce apoptosis and S-phase arrest in several cancer cell lines. In particular, compound 8b can prevent the proliferation of a non-small-cell lung cancer cell line (A549) through the Mcl-1/XIAP/PARP axis, in agreement with the unique modes of action of the combined agents of HDAC inhibitors and CDK inhibitors. In an A549 xerograph model, compound 8b showed significant antitumor efficacy correlated with its dual inhibition. Our data demonstrated that compound 8b as a single agent could be a promising drug candidate for cancer therapy in combination with CDK and HDAC inhibitors.