Antioxidant Mechanisms of Echinatin and Licochalcone A

Significance of Chalcone Scaffolds in Medicinal Chemistry

Chalcone is a simple naturally occurring α,β-unsaturated ketone with biological importance, which can also be easily synthesized in laboratories by reaction between two aromatic scaffolds. In plants, chalcones occur as polyphenolic compounds of different frameworks which are bioactive molecules that have been in traditional medicinal practice for many years. Chalcone-based lead molecules have been developed, possessing varied potentials such as antimicrobial, antiviral, anti-inflammatory, anticancer, anti-oxidant, antidiabetic, antihyperurecemic, and anti-ulcer effects. Chalcones contribute considerable fragments to give important heterocyclic molecules with therapeutic utilities targeting various diseases. These characteristic features have made chalcone a topic of interest among researchers and have attracted investigations into this widely applicable structure. This review highlights the extensive exploration carried out on the synthesis, biotransformations, chemical reactions, hybridization, and pharmacological potentials of chalcones, and aims to provide an extensive, thorough, and critical review of their importance, with emphasis on their properties, chemistry, and biomedical applications to boost future investigations into this potential scaffold in medicinal chemistry.

The Role of Licorice Chalcones as Molecular Genes and Signaling Pathways Modulator-A Review of Experimental Implications for Nicotine-Induced Non-Small Cell Lung Cancer Treatment

Lung cancer (LC) represents the leading cause of global cancer deaths, with cigarette smoking being considered a major risk factor. Nicotine is a major hazardous compound in cigarette smoke (CS), which stimulates LC progression and non-small cell lung cancer (NSCLC) specifically through activation of the nicotinic acetylcholine receptor (α7nAChR)-mediated cell-signaling pathways and molecular genes involved in proliferation, angiogenesis, and metastasis. Chalcones (CHs) and their derivatives are intermediate plant metabolites involved in flavonol biosynthesis. Isoliquiritigenin (ILTG), licochalcone A-E (LicoA-E), and echinatin (ECH) are the most common natural CHs isolated from the root of Glycyrrhiza (also known as licorice). In vitro and/or vivo experiments have shown that licorice CHs treatment exhibits a range of pharmacological effects, including antioxidant, anti-inflammatory, and anticancer effects. Despite advances in NSCLC treatment, the mechanisms of licorice CHs in nicotine-induced NSCLC treatment remain unknown. Therefore, the aim of this paper is to review experimental studies through the PubMed/Medline database that reveal the effects of licorice CHs and their potential mechanisms in nicotine-induced NSCLC treatment.

Echinatin attenuates acute lung injury and inflammatory responses via TAK1-MAPK/NF-κB and Keap1-Nrf2-HO-1 signaling pathways in macrophages

Echinatin is an active ingredient in licorice, a traditional Chinese medicine used in the treatment of inflammatory disorders. However, the protective effect and underlying mechanism of echinatin against acute lung injury (ALI) is still unclear. Herein, we aimed to explore echinatin-mediated anti-inflammatory effects on lipopolysaccharide (LPS)-stimulated ALI and its molecular mechanisms in macrophages. In vitro, echinatin markedly decreased the levels of nitric oxide (NO) and prostaglandin E2 (PGE2) in LPS-stimulated murine MH-S alveolar macrophages and RAW264.7 macrophages by suppressing inducible nitric oxide synthase and cyclooxygenase-2 (COX-2) expression. Furthermore, echinatin reduced LPS-induced mRNA expression and release of interleukin-1β (IL-1β) and IL-6 in RAW264.7 cells. Western blotting and CETSA showed that echinatin repressed LPS-induced activation of mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) pathways through targeting transforming growth factor-beta-activated kinase 1 (TAK1). Furthermore, echinatin directly interacted with Kelch-like ECH-associated protein 1 (Keap1) and activated the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway to enhance heme oxygenase-1 (HO-1) expression. In vivo, echinatin ameliorated LPS-induced lung inflammatory injury, and reduced production of IL-1β and IL-6. These findings demonstrated that echinatin exerted anti-inflammatory effects in vitro and in vivo, via blocking the TAK1-MAPK/NF-κB pathway and activating the Keap1-Nrf2-HO-1 pathway.

Synthesis and Antitumor Activity Evaluation of Novel Echinatin Derivatives with a 1,3,4-Oxadiazole Moiety

A series of novel echinatin derivatives with 1,3,4-oxadiazole moieties were designed and synthesized. Most of the newly synthesized compounds exhibited moderate antiproliferative activity against the four cancer cell lines. Notably, Compound T4 demonstrated the most potent activity, with IC50 values ranging from 1.71 µM to 8.60 µM against the four cancer cell lines. Cell colony formation and wound healing assays demonstrated that T4 significantly inhibited cell proliferation and inhibited migration. We discovered that T4 exhibited moderate binding affinity with the c-KIT protein through reverse docking. The results were effectively validated through subsequent molecular docking and c-KIT enzyme activity assays. In addition, Western blot analysis revealed that T4 inhibits the phosphorylation of downstream proteins of c-KIT. The results provide valuable inspiration for exploring novel insights into the design of echinatin-related hybrids as well as their potential application as c-KIT inhibitors to enhance the efficacy of candidates.

Licochalcone a improves cardiac functions after ischemia-reperfusion via reduction of ferroptosis in rats

Myocardial ischemia-reperfusion (I/R) injury triggers several cell death types, including apoptosis, autophagy, and ferroptosis. Licochalcone A (LCA), a natural flavonoid compound isolated from the root of Glycyrrhiza glabra, has been demonstrated to exert potential pharmacological benefits, such as antioxidant, antitumor, and anti-inflammatory activities. The present study aimed to investigate the involvement of ferroptosis in the pathogenesis of I/R and determine whether LCA can inhibit ferroptosis to prevent the myocardial I/R injury in rats. The effects of LCA on myocardial I/R injury were detected by examining the left ventricular-developed pressure and triphenyltetrazolium chloride staining. We conducted Western blotting analyses, ELISA assay, and quantitative real-time PCR to determine the levels of ferroptosis-related molecules. To demonstrate the cardioprotective effect of LCA in vitro, H9c2 and primary neonatal rat cardiomyocytes were co-treated with ferroptosis inducers (erastin, RSL3, or Fe-SP) and LCA for 16 and 24 h. Our ex vivo study showed that LCA increased the cardiac contractility, and reduced the infarct volume and ferroptosis-related biomarkers in rat hearts after I/R. Moreover, LCA reduced the levels of ferroptosis inducers-induced reactive oxygen species generation, lipid peroxidation, and ferroptosis-related biomarkers in cultured H9c2 cells and cardiomyocytes. LCA also reduced the Fe-SP-increased nuclear factor erythroid 2-related factor 2 and heme oxygenase-1 protein levels in cultured cardiomyocytes. In the present study, we showed that the LCA-induced cardioprotective effects in attenuating the myocardial I/R injury were correlated with ferroptosis regulation, and provided a possible new therapeutic strategy for prevention or therapy of the myocardial I/R injury.

Comparative analysis of flavonoid metabolites from different parts of Hemerocallis citrina

BACKGROUND

Hemerocallis citrina Baroni is a traditional medical and edible plant. It is rich in flavonoid compounds, which are a kind of important bioactive components with various health benefits and pharmaceutical value. However, the flavonoid metabolomics profile and the comparison of flavonoid compounds from different parts of H. citrina is scarce.

RESULTS

In this study, flavonoid metabolites were investigated from roots, stems, leaves and flowers of H. citrina. A total of 364 flavonoid metabolites were identified by UPLC-MS/MS based widely targeted metabolomics, and the four plant parts showed huge differences at flavonoid metabolic level. Compared to roots, 185, 234, and 119 metabolites accounted for upregulated differential flavonoid metabolites (DFMs) in stems, leaves, and flowers, respectively. Compared to stems, 168 and 29 flavonoid metabolites accounted for upregulated DFMs in leaves and flowers, respectively. Compared to leaves, only 29 flavonoid metabolites accounted for upregulated DFMs in flowers. A number of 35 common flavonoid metabolites were observed among six comparison groups, and each comparison group had its unique differential metabolites. The most abundant flavonoid metabolites in the four parts are flavonols and flavones, followed by flavanones, chalcones, flavanols, flavanonols, anthocyanidins, tannin, and proanthocyanidins. 6,7,8-Tetrahydroxy-5-methoxyflavone, 7,8,3',4'-tetrahydroxyflavone, 1-Hydroxy-2,3,8-trimethoxyxanthone, Farrerol-7-O-glucoside, 3',7-dihydroxy-4'-methoxyflavone, 3,3'-O-Dimethylellagic Acid, 5-Hydroxy-6,7-dimethoxyflavone, Nepetin (5,7,3',4'-Tetrahydroxy-6-methoxyflavone), (2s)-4,8,10-trihydroxy-2-methoxy-1 h,2 h-furo[3,2-a]xanthen-11-one are dominant in roots. Isorhamnetin-3-O-(6''-malonyl)glucoside-7-O-rhamnoside, 7-Benzyloxy-5-hydroxy-3',4'-methylenedioxyflavonoid, 3-Hydroxyphloretin-4'-O-glucoside are dominant in stems. Chrysoeriol-7-O-glucoside, Epicatechin glucoside, Kaempferol-3-O-rhamnoside (Afzelin)(Kaempferin)*, Azaleatin (5-O-Methylquercetin), Chrysoeriol-5-O-glucoside, Nepetin-7-O-glucoside(Nepitrin), 3,5,7,2'-Tetrahydroxyflavone; Datiscetin, Procyanidin B2*, Procyanidin B3*, Procyanidin B1, Isorhamnetin-3-O-(6''-acetylglucoside) are dominant in leaves. kaempferol-3-p-coumaroyldiglucoside, Delphinidin-3-O-sophoroside-5-O-glucoside, Limocitrin-3-O-sophoroside, Kaempferol-3-O-rutinoside(Nicotiflorin), Luteolin-7-O-(6''-malonyl)glucoside-5-O-rhamnoside are dominant in flowers.

CONCLUSION

There was significant difference in flavonoid metabolites among different parts of H. citrina. Leaves had relative higher metabolites contents than other parts. This study provided biological and chemical evidence for the different uses of various plant parts of H. citrina, and these informations are important theoretical basis for the food industry, and medical treatment.

Histone Deacetylase GiSRT2 Negatively Regulates Flavonoid Biosynthesis in Glycyrrhiza inflata

Glycyrrhiza inflata Batalin is a medicinal licorice species that has been widely used by humans for centuries. Licochalcone A (LCA) is a characteristic flavonoid that accumulates in G. inflata roots with high economical value. However, the biosynthetic pathway and regulatory network of its accumulation remain largely unknown. Here we found that a histone deacetylase (HDAC) inhibitor nicotinamide (NIC) could enhance the accumulation of LCA and total flavonoids in G. inflata seedlings. GiSRT2, a NIC-targeted HDAC was functionally analyzed and its RNAi transgenic hairy roots accumulated much more LCA and total flavonoids than its OE lines and the controls, indicating a negative regulatory role of GiSRT2 in the accumulation of LCA and total flavonoids. Co-analysis of transcriptome and metabolome of RNAi-GiSRT2 lines revealed potential mechanisms in this process. An O-methyltransferase gene, GiLMT1 was up-regulated in RNAi-GiSRT2 lines and the encoded enzyme catalyzed an intermediate step in LCA biosynthesis pathway. Transgenic hairy roots of GiLMT1 proved that GiLMT1 is required for LCA accumulation. Together, this work highlights the critical role of GiSRT2 in the regulation of flavonoid biosynthesis and identifies GiLMT1 as a candidate gene for the biosynthesis of LCA with synthetic biology approaches.

Hot-Air Drying Significantly Improves the Quality and Functional Activity of Orange Black Tea Compared with Traditional Sunlight Drying

The quality of traditional sunlight-dried orange black tea can be affected by weather variations, leading to its quality instability. This study investigated the feasibility of replacing sunlight drying with a new hot-air drying method in orange black tea production. The hot-air-dried orange black tea showed better sensory quality than the traditional outdoor-sunlight-dried tea, with a harmonious fruity aroma and sweet-mellow taste. The content of polyphenols and other quality components in the peel and tea leaves was significantly higher after hot-air drying than after sunlight drying. GC-MS analysis showed that the total number of volatile components of hot-air-dried tea (3103.46 μg/g) was higher than that of sunlight-dried tea (3019.19 μg/g). Compared with sunlight-dried orange black tea, the hot-air-dried orange black tea showed higher total antioxidant capacity, with an increase of 21.5% (FRAP), 7.5% (DPPH), and 17.4% (ABTS), as well as an increase of 38.1% and 36.3% in the inhibitory capacity on α-glucosidase and α-amylase activities. Further analysis of the effects of different drying temperatures (40, 45, 50, and 60 °C) on the quality of orange black tea showed that the tea quality gradually decreased with the increase in drying temperature, with the most obvious decrease in the quality of orange black tea at the drying temperature of 60 °C. Low-temperature (40 °C) dried tea had better aroma coordination, higher fruit flavor, greater sweet-mellow taste, and higher retention of functional active substances in orange peel and black tea. In summary, compared with traditional sunlight drying, the hot-air drying method could reduce the drying time from 90 h to 20 h and improve the sensory quality and functional activity of orange black tea, suggesting it can replace the traditional sunlight drying process. This work is significant for improving the quality of orange black tea in practical production.

Naturally Occurring Chalcones with Aggregation-Induced Emission Enhancement Characteristics

In this paper, the natural chalcones: 2'-hydroxy-4,4',6'-trimethoxychalcone (HCH), cardamonin (CA), xanthohumol (XN), isobavachalcone (IBC) and licochalcone A (LIC) are studied using spectroscopic techniques such as UV-vis, fluorescence spectroscopy, scanning electron microscopy (SEM) and single-crystal X-ray diffraction (XRD). For the first time, the spectroscopic and structural features of naturally occurring chalcones with varying numbers and positions of hydroxyl groups in rings A and B were investigated to prove the presence of the aggregation-induced emission enhancement (AIEE) effect. The fluorescence studies were carried out in the aggregate form in a solution and in a solid state. As to the results of spectroscopic analyses conducted in the solvent media, the selected mixtures (CH₃OH:H₂O and CH₃OH:ethylene glycol), as well as the fluorescence quantum yield (ϕ_F) and SEM, confirmed that two of the tested chalcones (CA and HCH) exhibited effective AIEE behaviour. On the other hand, LIC showed a large fluorescence quantum yield and Stokes shift in the polar solvents and in the solid state. Moreover, all studied compounds were tested for their promising antioxidant activities via the utilisation of 1,1- diphenyl-2-picrylhydrazyl as a free-radical scavenging reagent as well as potential anti-neurodegenerative agents via their ability to act as acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitors. Finally, the results demonstrated that licochalcone A, with the most desirable emission properties, showed the most effective antioxidant (DPPH IC₅₀ 29%) and neuroprotective properties (AChE IC₅₀ 23.41 ± 0.02 μM, BuChE IC₅₀ 42.28 ± 0.06 μM). The substitution pattern and the biological assay findings establish some relation between photophysical properties and biological activity that might apply in designing AIEE molecules with the specified characteristics for biological application.

The natural product, echinatin, protects mice from methicillin-resistant Staphylococcus aureus pneumonia by inhibition of alpha-hemolysin expression

Antimicrobial resistance (AMR) is a global, multifaceted crisis that poses significant challenges to the successful eradication of devastating pathogens, particularly methicillin-resistant Staphylococcus aureus (MRSA), a persistent superbug that causes devastating infections. The scarcity of new antibacterial drugs is obvious, and antivirulence strategies that reduce the pathogenicity of bacteria by weakening their virulence have become the subject of intense investigation. Alpha-hemolysin (Hla), a cytolytic pore-forming toxin, has a pivotal role in S. aureus pathogenesis. Here, we demonstrated that echinatin, a natural compound isolated from licorice, effectively inhibited the hemolytic activity of MRSA at 32 μg/mL. In addition, echinatin did not interfere with bacterial growth and had no significant cytotoxicity at the inhibitory concentration of S. aureus hemolysis. Heptamer formation tightly correlated with Hla-mediated cell invasion, whereas echinatin did not affect deoxycholic acid-induced oligomerization of Hla. Echinatin affected hemolytic activity through indirect binding to Hla as confirmed by the neutralization assay and cellular thermal shift assay (CETSA). Furthermore, qRT-PCR and western blot analyses revealed that echinatin suppressed Hla expression at both the mRNA and protein levels as well as the transcript levels of Agr quorum-sensing system-related genes. Additionally, when echinatin was added to a coculture system of A549 cells and S. aureus, it significantly reduced cell damage. Importantly, echinatin exhibited a significant therapeutic effect in an MRSA-induced mouse pneumonia model. In conclusion, the present findings demonstrated that echinatin significantly inhibits the hemolysin effect and may be a potential candidate compound for combating drug-resistant MRSA infections.

Echinatin mitigates sevoflurane-induced hippocampal neurotoxicity and cognitive deficits through mitigation of iron overload and oxidative stress

CONTEXT

Sevoflurane (Sev) is a commonly used surgical anaesthetic; it has neurotoxic effects on the brain. Echinatin (Ech) is reported to have anti-inflammatory and antioxidant activity.

OBJECTIVE

This research confirms the effect of Ech on Sev-induced neurotoxicity and cognitive deficits.

MATERIALS AND METHODS

Primary rat hippocampal neurons were treated with 4.1% Sev for 6 h in the presence of Ech (5, 10, and 20 μM) or vehicle, followed by a further 42 h of culture. Male Sprague-Dawley aged rats were divided into 6 groups (n = 6): control, Sev, Sev + Ech (20 mg/kg;), Sev + Ech (40 mg/kg), and Sev + Ech (80 mg/kg). Rats were intraperitoneally injected with Ech or vehicle 1 h before Sev exposure (2% Sev for 5 h).

RESULTS

We found that Ech (5, 10, and 20 μM) elevated cell viability (1.29-, 1.51-, 1.68-fold) but mitigated apoptosis (23.87% vs. 16.48%, 12.72%, 9.02%), oxidative stress, and ferroptosis in hippocampal neurons with Sev treatment. Ech activated the Nrf2 expression in Sev-induced in vitro and in vivo models of anaesthetic neurotoxicity. Ech also weakened neurotoxicity in hippocampal neurons with Sev treatment by increasing Nrf2 expression level. Moreover, Ech alleviated hippocampus neurons apoptosis (19.38% vs. 16.05%, 11.71%, 8.88%), oxidative stress, and ferroptosis in rats with Sev treatment. Ech improved Sev-induced cognitive deficits in rats.

CONCLUSIONS

Ech alleviates Sev-induced neurotoxicity and cognitive deficits by mitigation of ferroptosis and oxidative stress. Ech may be developed as a new promising therapeutic drug for treatment of cerebral nerve injury caused by surgical anaesthesia.

Recent advances in the antioxidant activity and mechanisms of chalcone derivatives: a computational review

In this review, we have reported the antioxidant mechanisms and structure-antioxidant activity relationship of several chalcone derivatives, investigated in the recent past, based on the density functional theory (DFT) calculations, considering free radical scavenging and metal chelation ability. The antioxidant mechanisms include hydrogen atom transfer (HAT), sequential proton loss electron transfer (SPLET), single electron transfer followed by proton transfer (SET-PT), sequential proton loss hydrogen atom transfer (SPLHAT), sequential double proton loss electron transfer (SdPLET), sequential triple proton loss double electron transfer (StPLdET), sequential triple proton loss triple electron transfer (StPLtET), double HAT, double SPLET, double SET-PT, triple HAT, triple SET-PT, triple SPLET, proton-coupled electron transfer (PCET), single electron transfer (SET), radical adduct formation (RAF) and radical adduct formation followed by hydrogen atom abstraction (RAF-HAA). Furthermore, solvent effects have also been considered using different solvation models. The feasibility of scavenging different reactive oxygen and nitrogen species (ROS/RNS) has been discussed considering various factors such as the number and position of hydroxyl as well as methoxy groups present in the antioxidant molecule, stability of the species formed after scavenging reactive species, nature of substituent, steric effects, etc. This review opens new perspectives for designing new compounds with better antioxidant potential.

Phytophenol Dimerization Reaction: From Basic Rules to Diastereoselectivity and Beyond

Phytophenol dimerization, which is a radical-mediated coupling reaction, plays a critical role in many fields, including lignin biosynthesis. To understand the reaction, 2,2-diphenyl-1-picrylhydrazyl radical was used to initiate a series of phytophenol dimerization reactions in methanol. The products were identified using ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UHPLC-ESI-Q-TOF-MS/MS) analysis in situ. The identified products mainly included biphenols, magnolol, honokiol, gingerol 6,6′-dimers, 3,6-dimethoxylcatechol β,β′ dimer, euphorbetin, bis-eugenol, dehydrodiisoeugenol, trans-ε-viniferin, (+) pinoresinol, and (−) pinoresinol. Structure–function relationship analysis allowed four basic rules to be defined: meta-excluded, C–C bonding domination, ortho-diOH co-activation, and exocyclic C=C involvement. The exocyclic C=C involvement, however, required conjugation with the phenolic core and the para-site of the -OH group, to yield a furan-fused dimer with two chiral centers. Computational chemistry indicated that the entire process was completed via a radical coupling reaction and an intramolecular conjugate addition reaction. Similar results were also found for the horseradish peroxidase (HRP)-catalyzed coniferyl alcohol dimerization, which produced (+) and (−) pinoresinols (but no (−) epipinoresinol), suggesting that the HRP-catalyzed process was essentially an exocyclic C=C-involved phytophenol dimerization reaction. The reaction was highly diastereoselective. This was attributed to the intramolecular reaction, which prohibited Re-attack. The four basic rules and diastereoselectivity can explain and even predict the main products in various chemical and biological events, especially oxidase-catalyzed lignin cyclization.

Natural-like Chalcones with Antitumor Activity on Human MG63 Osteosarcoma Cells

Osteosarcoma (OS) is a malignant disease characterized by poor prognosis due to a high incidence of metastasis and chemoresistance. Recently, Licochalcone A (Lic-A) has been reported as a promising agent against OS. Starting from chalcones selected from a wide in-house library, a new series was designed and synthetized. The antitumor activity of the compounds was tested on the MG63 OS cell line through the innovative Quantitative Phase Imaging technique and MTT assay. To further investigate the biological profile of active derivatives, cell cycle progression and apoptosis induction were evaluated. An earlier and more consistent arrest in the G2-M phase with respect to Lic-A was observed. Moreover, apoptosis was assessed by Annexin V staining as well as by the detection of typical morphological features of apoptotic cells. Among the selected compounds, 1e, 1q, and 1r proved to be the most promising antitumor molecules. This study pointed out that an integrated methodological approach may constitute a valuable platform for the rapid screening of large series of compounds.

Ferroptosis-Inhibitory Difference between Chebulagic Acid and Chebulinic Acid Indicates Beneficial Role of HHDP

The search for a safe and effective inhibitor of ferroptosis, a recently described cell death pathway, has attracted increasing interest from scientists. Two hydrolyzable tannins, chebulagic acid and chebulinic acid, were selected for the study. Their optimized conformations were calculated using computational chemistry at the B3LYP-D3(BJ)/6-31G and B3LYP-D3(BJ)/6-311 + G(d,p) levels. The results suggested that (1) chebulagic acid presented a chair conformation, while chebulinic acid presented a skew-boat conformation; (2) the formation of chebulagic acid requires 762.1729 kcal/mol more molecular energy than chebulinic acid; and (3) the 3,6-HHDP (hexahydroxydiphenoyl) moiety was shown to be in an (R)- absolute stereoconfiguration. Subsequently, the ferroptosis inhibition of both tannins was determined using a erastin-treated bone marrow-derived mesenchymal stem cells (bmMSCs) model and compared to that of ferrostatin-1 (Fer-1). The relative inhibitory levels decreased in the following order: Fer-1 > chebulagic acid > chebulinic acid, as also revealed by the in vitro antioxidant assays. The UHPLC-ESI-Q-TOF-MS analysis suggested that, when treated with 16-(2-(14-carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinyloxy free radicals, Fer-1 generated dimeric products, whereas the two acids did not. In conclusion, two hydrolyzable tannins, chebulagic acid and chebulinic acid, can act as natural ferroptosis inhibitors. Their ferroptosis inhibition is mediated by regular antioxidant pathways (ROS scavenging and iron chelation), rather than the redox-based catalytic recycling pathway exhibited by Fer-1. Through antioxidant pathways, the HHDP moiety in chebulagic acid enables ferroptosis-inhibitory action of hydrolyzable tannins.

A New Chalcone Derivative C49 Reverses Doxorubicin Resistance in MCF-7/DOX Cells by Inhibiting P-Glycoprotein Expression

Objective: C49 is a chalcone derivative. The aim of the current study is to illuminate the efficacy of C49 in reversing multidrug resistance (MDR) in MCF-7/DOX cells and its underlying molecular mechanism. Methods: The cytotoxic effects of C49 on MCF-7/DOX cells were evaluated by MTT assay using different concentration (0-250 μmol/L) of C49. Cell proliferation was evaluated by colony formation assay. Cell death was examined by morphological analysis using Hoechst 33,258 staining. Flow cytometry and immunofluorescence were utilized to evaluate the intracellular accumulation of doxorubicin (DOX) and cell apoptosis. The differentially expressed genns between MCF-7 and MCF-7/DOX cells were analyzed by GEO database. The expression of PI3K/Akt pathway proteins were assessed by Western blot The activities of C49 combined with DOX was evaluated via xenograft tumor model in female BALB/c nude mice. Results: C49 inhibited the growth of MCF-7 cells (IC₅₀ = 59.82 ± 2.10 μmol/L) and MCF-7/DOX cells (IC₅₀ = 65.69 ± 8.11 μmol/L) with dosage-dependent and enhanced the cellular accumulation of DOX in MCF-7/DOX cells. The combination of C49 and DOX inhibited cell proliferation and promoted cell apoptosis. MCF-7/DOX cells regained drug sensibility with the combination treatment through inhibiting the expression of P-gp, p-PI3K and p-Akt proteins. Meanwhile, C49 significantly increased the anticancer efficacy of DOX in vivo. Conclusion: C49 combined with DOX restored DOX sensitivity in MCF-7/DOX cells through inhibiting P-gp protein.

Licochalcone A improves the cognitive ability of mice by regulating T- and B-cell proliferation

Licochalcone A (LA), a flavonoid found in licorice, has anticancer, antioxidant, anti-inflammatory, and neuroprotective properties. Here, we explored the effect of injecting LA into the tail vein of middle-aged C57BL/6 mice on their cognitive ability as measured by the Morris water maze (MWM) test and cerebral blood flow (CBF). The related mechanisms were assessed via RNA-seq, and T (CD3e⁺) and B (CD45R/B220⁺) cells in the spleen and whole blood were quantified via flow cytometry. LA improved the cognitive ability, according to the MWM test results, and upregulated the CBF level of treated mice. The RNA-seq results indicate that LA affected the interleukin (IL)-17 signaling pathway, which is related to T- and B-cell proliferation, and the flow cytometry data suggest that LA promoted T- and B-cell proliferation in the spleen and whole blood. We also performed immune reconstruction via a tail vein injection of lymphocytes into B-NDG (NOD-Prkdc^scidIl2rg^tm1/Bcge) mice before treating them with LA. We tested cognitive ability by subjecting these animals to new object recognition tests and quantified the splenic and whole blood T and B cells. Cognitive ability improved after immune reconstruction and LA treatment, and LA promoted T- and B-cell proliferation in the spleen and whole blood. This study demonstrates that LA, by activating the IL-17 signaling pathway, promotes T- and B-cell proliferation in the spleen and whole blood of mice and improves cognitive ability. Thus, LA may have immune-modulating therapeutic potential for improving cognition.

Cardioprotective Effect of Echinatin Against Ischemia/Reperfusion Injury: Involvement of Hippo/Yes-Associated Protein Signaling

Background: Echinatin (Ech) has been reported to exert antioxidant and anti-inflammatory activities. In this study, we aimed to characterize the functional role of Ech in myocardial ischemic/reperfusion (MI/R) injury and elucidate its underlying mechanism of action.

Method: We established in vivo and in vitro models of MI/R injury to determine the effect of Ech on MI/R injury. Gene expression was examined using quantitative real-time polymerase chain reaction and western blotting. Myocardial infarction was assessed using tetrazolium chloride staining and the degree of myocardial injury was evaluated by measuring lactate dehydrogenase (LDH) and creatine kinase-myocardial band (CK-MB) levels. Cell apoptosis was detected using the terminal deoxynucleotidyl transfer-mediated dUTP nick end-labeling (TUNEL) assay. The viability of H9c2 cells was determined using Cell Counting Kit-8 assay.

Results: MI/R induced myocardial infarction, which was mitigated by Ech treatment. Moreover, Ech treatment resulted in a marked decline of LDH and CK-MB levels in the serum and myocardium of MI/R rats. Ech treatment also restrained cardiomyocyte apoptosis in vivo and in vitro, as evidenced by reduction in LDH release, the number of TUNEL-positive cells, and caspase-3 activity. Furthermore, Ech administration inhibited MI/R-induced activation of Hippo/Yes-associated protein signaling in vivo and in vitro, as indicated by inhibition of mammalian sterile 20-like protein kinase 1, large tumor suppressor one, and YAP phosphorylation and promotion of YAP nuclear translocation. However, silencing of YAP counteracted the protective effect of Ech on hypoxia/reoxygenation-induced myocardial injury in vitro.

Conclusion: Ech exerted its protective effect against MI/R injury at least partially by suppressing the Hippo/YAP signaling pathway, providing novel insights into the remission of MI/R injury.

ERK Activation-Mediated Autophagy Induction Resists Licochalcone A-Induced Anticancer Activities in Lung Cancer Cells in vitro

Introduction

The incidence and mortality rates of lung cancer rank top in the different types of cancers in China. Licochalcone A (LA) is a flavonoid extracted from the roots of licorice with antitumor effects in various cancers in vitro and in vivo. However, the role of LA in non-small cell lung cancer (NSCLC) remains largely unclear.

Methods

The cell viability was measured by MTT assay, Edu staining and colony formation assay. Apoptosis was investigated using Annexin V/PI double-stained assays with flow cytometry. Real-time quantitative RT-PCR was carried out to investigate the expression of mRNA of related proteins. Western blotting was used to investigate the expression of related proteins.

Results

The results show that LA inhibits the proliferation of NSCLC cells in a dose-dependent manner and induces apoptotic cell death. Moreover, LA significantly suppresses the expression of c-IAP1, c-IAP2, XIAP, Survivin, c-FLIP_L and RIP1 without influencing the level of mRNA. Cycloheximide chase assay demonstrates that LA greatly decreases the stability of Survivin, XIAP and RIP1. Mechanistic studies indicate that LA induces cytoprotective autophagy since block of autophagy with CQ greatly enhances LA-induced anticancer activities. Furthermore, LA rapidly induces ERK and p38 activation in a time-dependent manner in both A549 and H460 cells, but suppresses the activities of c-Jun N-terminal kinase (JNK); suppression of ERK not p38 with inhibitor attenuates LA-induced autophagy, while it remarkably enhances LA-induced cytotoxicity in lung cancer cells and further promotes the degradation of apoptosis-related proteins.

Discussion

The results of this study provide novel insights on the role of apoptosis-related proteins and the MAPKs pathway in the anticancer activities of LA.

Antioxidant product analysis of Hulu Tea (Tadehagi triquetrum)

Phytophenols from Hulu Tea can produce not only homodimers but also a heterodimer through the antioxidant activity.

Licochalcone a Exhibits Leishmanicidal Activity in vitro and in Experimental Model of Leishmania (Leishmania) Infantum

The efficacy of Licochalcone A (LicoA) and its two analogs were reported against Leishmania (Leishmania) amazonensis and Leishmania (Leishmania) infantum in vitro, and in experimental model of L. (L.) infantum in vitro. Initially, LicoA and its analogs were screened against promastigote forms of L. (L.) amazonensis. LicoA was the most active compound, with IC50 values of 20.26 and 3.88 μM at 24 and 48 h, respectively. Against amastigote forms, the IC50 value of LicoA was 36.84 μM at 48 h. In the next step, the effectivity of LicoA was evaluated in vitro against promastigote and amastigote forms of L. (L.) infantum. Results demonstrated that LicoA exhibited leishmanicidal activity in vitro against promastigote forms with IC50 values of 41.10 and 12.47 μM at 24 and 48 h, respectively; against amastigote forms the IC50 value was 29.58 μM at 48 h. Assessment of cytotoxicity demonstrated that LicoA exhibited moderate mammalian cytotoxicity against peritoneal murine macrophages; the CC50 value was 123.21 μM at 48 h and showed about 30% of hemolytic activity at concentration of 400 μM. L. (L.) infantum-infected hamsters and treated with LicoA at 50 mg/kg for eight consecutive days was able to significantly reduce the parasite burden in both liver and spleen in 43.67 and 39.81%, respectively, when compared with negative control group. These findings suggest that chalcone-type flavonoids can be a promising class of natural products to be considered in the search of new, safe, and effective compounds capable to treat canine visceral leishmaniosis (CVL).

The Antioxidant Capacities of Natural Products 2019

The search for new natural antioxidants is a growing area of research due to the broad spectrum of their biological properties, which are associated with the prevention of chronic diseases that originate in oxidative stress [...].

Echinatin suppresses esophageal cancer tumor growth and invasion through inducing AKT/mTOR-dependent autophagy and apoptosis

Esophageal squamous cell carcinoma (ESCC) is one of the most common malignant tumors with poor survival. It is urgent to search for new efficient drugs with good stability and safety for clinical therapy. This study aims to identify potential anticancer drugs from a compound library consisting of 429 natural products. Echinatin, a compound isolated from the Chinese herb Glycyrrhiza uralensis Fisch, was found to markedly induce apoptosis and inhibit proliferation and colony-formation ability in ESCC. Confocal fluorescence microscopy data showed that echinatin significantly induced autophagy in ESCC cells, and autophagy inhibitor bafilomycinA1 attenuated the suppressive effects of echinatin on cell viability and apoptosis. Mechanistically, RNA sequencing coupled with bioinformatics analysis and a series of functional assays revealed that echinatin induced apoptosis and autophagy through inactivation of AKT/mTOR signaling pathway, whereas constitutive activation of AKT significantly abrogated these effects. Furthermore, we demonstrated that echinatin had a significant antitumor effect in the tumor xenograft model and markedly suppressed cell migration and invasion abilities of ESCC cells in a dose-dependent manner. Our findings provide the first evidence that echinatin could be a novel therapeutic strategy for treating ESCC.

Simultaneous Study of Anti-Ferroptosis and Antioxidant Mechanisms of Butein and (S)-Butin

To elucidate the mechanism of anti-ferroptosis and examine structural optimization in natural phenolics, cellular and chemical assays were performed with 2'-hydroxy chalcone butein and dihydroflavone (S)-butin. C11-BODIPY staining and flow cytometric assays suggest that butein more effectively inhibits ferroptosis in erastin-treated bone marrow-derived mesenchymal stem cells than (S)-butin. Butein also exhibited higher antioxidant percentages than (S)-butin in five antioxidant assays: linoleic acid emulsion assay, Fe3+-reducing antioxidant power assay, Cu2+-reducing antioxidant power assay, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide radical (PTIO•)-trapping assay, and α,α-diphenyl-β-picrylhydrazyl radical (DPPH•)-trapping assay. Their reaction products with DPPH• were further analyzed using ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC-ESI-Q-TOF-MS). Butein and (S)-butin produced a butein 5,5-dimer (m/z 542, 271, 253, 225, 135, and 91) and a (S)-butin 5',5'-dimer (m/z 542, 389, 269, 253, and 151), respectively. Interestingly, butein forms a cross dimer with (S)-butin (m/z 542, 523, 433, 419, 415, 406, and 375). Therefore, we conclude that butein and (S)-butin exert anti-ferroptotic action via an antioxidant pathway (especially the hydrogen atom transfer pathway). Following this pathway, butein and (S)-butin yield both self-dimers and cross dimers. Butein displays superior antioxidant or anti-ferroptosis action to (S)-butin. This can be attributed the decrease in π-π conjugation in butein due to saturation of its α,β-double bond and loss of its 2'-hydroxy group upon biocatalytical isomerization.

Antioxidant and Cytoprotective effects of Pyrola decorata H. Andres and its five phenolic components

Background

Pyrola decorata H. Andres, is exclusively distributed in China and a source of traditional Chinese herbal medicine Luxiancao for more than 2000 years. Here, we evaluated the antioxidant and cytoprotective effects of P. decorata and its five phenolic components (protocatechuic acid, gallic acid, hyperoside, 2′′-O-galloylhyperin, and quercetin), and discussed their antioxidant chemistry.

Methods

A lyophilized aqueous extract of P. decorata (LAEP) was prepared and analyzed with high-performance liquid chromatography (HPLC). LAEP and its five phenolic components were comparatively investigated using five antioxidant assays, including ferric-reducing antioxidant power, cupric ion-reducing antioxidant capacity, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide radical (PTIO^•)-scavenging, 1,1-diphenyl-2-picryl-hydrazl radical (DPPH^•)-scavenging, and 2,2′-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid) radical (ABTS^+•)-scavenging activities. The reaction products of the five phenolic components with 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl radical (4-methoxy-TEMPO^•) were determined with ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC-ESI-Q-TOF-MS/MS) analysis. LAEP and its five phenolic components were incubated with bone marrow-derived mesenchymal stem cells (bmMSCs) subjected to oxidative stress to demonstrate their cytoprotective effects with a flow cytometry assay.

Results

In the five antioxidant assays, LAEP and its five phenolic components dose-dependently increased the radical-scavenging (or reducing power) activities. However, the IC₅₀ values of hyperoside were consistently higher than those of 2′′-O-galloylhyperin. UPLC-ESI-Q-TOF-MS/MS analysis results indicated that the five phenolics could yield dimer products in the presence of 4-methoxy-TEMPO^• via the radical adduct formation (RAF) pathway. Flow cytometry assay results confirmed the cytoprotective activity of LAEP and its five phenolic components toward stressed bmMSCs. In particular, 2′′-O-galloylhyperin could more effectively reduce the percentage of damaged bmMSCs than hyperoside.

Conclusion

LAEP and its five phenolic components may undergo redox-based pathways (such as electron transfer and H⁺ transfer) and covalent-based pathway (i.e., RAF) to exhibit antioxidant activity. One consequence of RAF is the generation of phenolic-phenolic dimer. In both organic and aqueous media, 2′′-O-galloylhyperin exhibited higher redox-based antioxidant levels (or cytoprotective levels) than those with hyperoside. The differences could be attributed to 2′′-O-galloylation reaction.

Evaluation of Selected Natural Compounds as Dual Inhibitors of Catechol-O-Methyltransferase and Monoamine Oxidase

Background:

The most effective symptomatic treatment of Parkinson’s disease remains the metabolic precursor of dopamine, L-dopa. To enhance the efficacy of L-dopa, it is often combined with inhibitors of the enzymes, catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO) B, key metabolic enzymes of L-dopa and dopamine.

Objective:

This study attempted to discover compounds that exhibit dual inhibition of COMT and MAO-B among a library of 40 structurally diverse natural compounds. Such dual acting inhibitors may be effective as adjuncts to L-dopa and offer enhanced value in the management of Parkinson’s disease.

Methods:

Selected natural compounds were evaluated as in vitro inhibitors of rat liver COMT and recombinant human MAO. Reversibility of MAO inhibition was investigated by dialysis.

Results:

Among the natural compounds morin (IC50 = 1.32 µM), chlorogenic acid (IC50 = 6.17 µM), (+)-catechin (IC50 = 0.86 µM), alizarin (IC50 = 0.88 µM), fisetin (IC50 = 5.78 µM) and rutin (IC50 = 25.3 µM) exhibited COMT inhibition. Among these active COMT inhibitors only morin (IC50 = 16.2 µM), alizarin (IC50 = 8.16 µM) and fisetin (IC50 = 7.33 µM) were noteworthy MAO inhibitors, with specificity for MAO-A.

Conclusion:

None of the natural products investigated here are dual COMT/MAO-B inhibitors. However, good potency COMT inhibitors have been identified, which may serve as leads for future development of COMT inhibitors.

Anti-Proliferative and Pro-Apoptotic Effects of Licochalcone A through ROS-Mediated Cell Cycle Arrest and Apoptosis in Human Bladder Cancer Cells

Licochalcone A (LCA) is a chalcone that is predominantly found in the root of Glycyrrhiza species, which is widely used as an herbal medicine. Although previous studies have reported that LCA has a wide range of pharmacological effects, evidence for the underlying molecular mechanism of its anti-cancer efficacy is still lacking. In this study, we investigated the anti-proliferative effect of LCA on human bladder cancer cells, and found that LCA induced cell cycle arrest at G2/M phase and apoptotic cell death. Our data showed that LCA inhibited the expression of cyclin A, cyclin B1, and Wee1, but increased the expression of cyclin-dependent kinase (Cdk) inhibitor p21WAF1/CIP1, and increased p21 was bound to Cdc2 and Cdk2. LCA activated caspase-8 and -9, which are involved in the initiation of extrinsic and intrinsic apoptosis pathways, respectively, and also increased caspase-3 activity, a typical effect caspase, subsequently leading to poly (ADP-ribose) polymerase cleavage. Additionally, LCA increased the Bax/Bcl-2 ratio, and reduced the integrity of mitochondria, which contributed to the discharge of cytochrome c from the mitochondria to the cytoplasm. Moreover, LCA enhanced the intracellular levels of reactive oxygen species (ROS); however, the interruption of ROS generation using ROS scavenger led to escape from LCA-mediated G2/M arrest and apoptosis. Collectively, the present data indicate that LCA can inhibit the proliferation of human bladder cancer cells by inducing ROS-dependent G2/M phase arrest and apoptosis.

Comparative Analysis of Radical Adduct Formation (RAF) Products and Antioxidant Pathways between Myricetin-3-O-Galactoside and Myricetin Aglycone

The biological process, 3-O-galactosylation, is important in plant cells. To understand the mechanism of the reduction of flavonol antioxidative activity by 3-O-galactosylation, myricetin-3-O-galactoside (M3OGa) and myricetin aglycone were each incubated with 2 mol α,α-diphenyl-β-picrylhydrazyl radical (DPPH^•) and subsequently comparatively analyzed for radical adduct formation (RAF) products using ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC-ESI-Q-TOF-MS) technology. The analyses revealed that M3OGa afforded an M3OGa–DPPH adduct (m/z 873.1573) and an M3OGa–M3OGa dimer (m/z 958.1620). Similarly, myricetin yielded a myricetin–DPPH adduct (m/z 711.1039) and a myricetin–myricetin dimer (m/z 634.0544). Subsequently, M3OGa and myricetin were compared using three redox-dependent antioxidant analyses, including DPPH^•-trapping analysis, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide radical (PTIO^•)-trapping analysis, and ^•O₂ inhibition analysis. In the three analyses, M3OGa always possessed higher IC₅₀ values than those of myricetin. Conclusively, M3OGa and its myricetin aglycone could trap the free radical via a chain reaction comprising of a propagation step and a termination step. At the propagation step, both M3OGa and myricetin could trap radicals through redox-dependent antioxidant pathways. The 3-O-galactosylation process, however, could limit these pathways; thus, M3OGa is an inferior antioxidant compared to its myricetin aglycone. Nevertheless, 3-O-galactosylation has a negligible effect on the termination step. This 3-O-galactosylation effect has provided novel evidence that the difference in the antioxidative activities of phytophenols exists at the propagation step rather than the termination step.

Licochalcone A Suppresses the Proliferation of Osteosarcoma Cells through Autophagy and ATM-Chk2 Activation

Licochalcone A, a flavonoid extracted from licorice root, has been shown to exhibit broad anti-inflammatory, anti-bacterial, anticancer, and antioxidative bioactivity. In this study, we investigated the antitumor activity of Licochalcone A against human osteosarcoma cell lines. The data showed that Licochalcone A significantly suppressed cell viability in MTT assay and colony formation assay in osteosarcoma cell lines. Exposure to Licochalcone A blocked cell cycle progression at the G2/M transition and induced extrinsic apoptotic pathway in osteosarcoma cell lines. Furthermore, we found the Licochalcone A exposure resulted in rapid ATM and Chk2 activation, and high levels of nuclear foci of phosphorylated Chk2 at Thr 68 site in osteosarcoma cell lines. In addition, Licochalcone A exposure significantly induced autophagy in osteosarcoma cell lines. When Licochalcone A-induced autophagy was blocked by the autophagy inhibitor chloroquine, the expression of activated caspase-3 and Annexin V positive cells were reduced, and cell viability was rescued in Licochalcone A-treated osteosarcoma cell lines. These data indicate that the activation of ATM-Chk2 checkpoint pathway and autophagy may contribute to Licochalcone A-induced anti-proliferating effect in osteosarcoma cell lines. Our findings display the possibility that Licochalcone A may serve as a potential therapeutic agent against osteosarcoma.

3',8″-Dimerization Enhances the Antioxidant Capacity of Flavonoids: Evidence from Acacetin and Isoginkgetin

To probe the effect of 3',8″-dimerization on antioxidant flavonoids, acacetin and its 3',8″-dimer isoginkgetin were comparatively analyzed using three antioxidant assays, namely, the ·O₂^- scavenging assay, the Cu²⁺ reducing assay, and the 2,2'-azino bis(3-ethylbenzothiazolin-6-sulfonic acid) radical scavenging assay. In these assays, acacetin had consistently higher IC₅₀ values than isoginkgetin. Subsequently, the acacetin was incubated with 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxy radicals (4-methoxy-TEMPO) and then analyzed by ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UHPLC-ESI-Q-TOF-MS) technology. The results of the UHPLC-ESI-Q-TOF-MS analysis suggested the presence of a dimer with m/z 565, 550, 413, 389, 374, 345, 330, and 283 peaks. By comparison, standard isoginkgetin yielded peaks at m/z 565, 533, 518, 489, 401, 389, 374, and 151 in the mass spectra. Based on these experimental data, MS interpretation, and the relevant literature, we concluded that isoginkgetin had higher electron transfer potential than its monomer because of the 3',8″-dimerization. Additionally, acacetin can produce a dimer during its antioxidant process; however, the dimer is not isoginkgetin.

Design and Synthesis of a Fluorescent Probe with a Large Stokes Shift for Detecting Thiophenols and Its Application in Water Samples and Living Cells

A turn-on florescent probe (probe-KCP) was developed for highly selective detection of thiophenols based on a donor-excited photo-induced electron transfer mechanism. Herein, the synthesis of the probe, a chalcone derivative, through a simple straightforward combination of a carbazole-chalcone fluorophore with a 2,4-dinitrophenyl functional group. In a kinetic study of the probe-KCP for thiophenols, the probe displayed a short response time (~30 min) and significant fluorescence enhancement. In selection and competition experiments, the probe-KCP exhibited excellent selectivity for thiophenols over glutathione (GSH), cysteine (Cys), sodium hydrosulfide (NaSH), and ethanethiol (C₂H₅SH) in addition to common anions and metal ions. Using the designed probe, we successfully monitored and quantified thiophenols, which are highly toxic. This turn-on fluorescence probe features a remarkably large Stokes shift (130 nm) and a short response time (30 min), and it is highly selective and sensitive (~160-fold) in the detection of thiophenols, with marked fluorescence in the presence of thiophenols. probe-KCP responds to thiophenols with a good range of linearity (0–15 μM) and a detection limit of 28 nM (R² = 0.9946) over other tested species mentioned including aliphatic thiols, thiophenol analogues, common anions, and metal ions. The potential applications of this carbazole-chalcone fluorescent probe was successfully used to determine of thiophenols in real water samples and living cells with good performance and low cytotoxicity. Therefore, this probe has great potential application in environment and biological samples.