Homodimers of Vanillin and Apocynin Decrease the Metastatic Potential of Human Cancer Cells by Inhibiting the FAK/PI3K/Akt Signaling Pathway

A comprehensive update on phytochemistry and medicinal developments of apocynin

The natural phenolic compound apocynin, referred to as acetovanillone, generated significant attention due to its diverse pharmacological properties, especially as an NADPH oxidase inhibitor, and it was applicable orally and effectively even at small doses. During chronic inflammation, various pro-inflammatory-related factors such as nuclear factor kappa β (NF-kβ), nitrotyrosine, poly adenosine diphosphate ribose polymerase (PARP), inducible nitric oxide synthase (iNOS), cluster of differentiation 31 (CD31), intercellular adhesion molecule-1 (ICAM-1), glycoproteins granule membrane protein 140 (GMP140), tumor necrosis factor-alpha (TNFα), p38 mitogen-activated protein kinases (p38 MAPK), membrane cofactor protein (MCP), interleukin-6 (IL-6), all of which could be targeted by apocynin. Research suggests that apocynin significantly benefits conditions like diabetes, cardiovascular diseases, and neurological disorders due to its ability to mitigate inflammation and enhance endothelial function. Further investigations are essential to examine apocynin and its derivatives, mainly its long-term potency. Future research must focus on clinical trials to evaluate its safety, effectiveness, and optimal dosing in various applications. This review provides a recent update on apocynin, covering aspects such as its extraction and isolation, chemical framework, biosynthesis, synthetic derivatives, pharmacological activities, patent landscape, stability and specifications.

Assessing diapocynin's different effects on osteosarcoma and breast cancer cells: An in vitro study

Osteosarcoma is the most common primary bone cancer, accounting for approximately 5 % of new cancer cases globally. In contrast, breast cancer remains the most prevalent malignancy and a leading cause of cancer-related mortality among women. Given the limitations of current therapies, novel treatment strategies are urgently needed. This study evaluates the effects of diapocynin, a derivative of apocynin, on osteosarcoma (UMR-106) and breast cancer (MDA-MB-231) cell lines. Our results demonstrate a dose-dependent cytotoxicity of diapocynin in both cell types, with UMR-106 cells showing higher sensitivity than MDA-MB-231 cells. Notably, treatment with diapocynin induced significant morphological changes in both cell lines, and both IC25 and IC50 concentrations effectively inhibited cell migration, particularly in osteosarcoma cells. However, no significant changes were detected in matrix metalloproteinases -2 and -9 activity following treatment, suggesting that diapocynin may exert its effects through alternative pathways. These results highlight diapocynin as a promising candidate for cancer therapy, warranting further investigation into its mechanisms of action and potential clinical applications.

Effect of NADPH oxidase inhibitor apocynin on human lung cancer A549 cells via Bcl-2, Bax, caspase-3, and NF-κB signaling pathway

Apocynin (AP) is an anti-inflammatory drug with different therapeutic effects. This study aimed to investigate the antiproliferative, apoptotic, and antioxidant effects of AP on human lung adenocarcinoma cells (A549) and to investigate the effects on Bax, Bcl-2, NF-κB, and caspase-3 signaling pathways that may play a role in the pathogenesis of lung cancer. Cell viability was measured by MTT and cell apoptosis, and detection of cell death was measured by ELISA. IMA, AOPP, MDA, and GSH levels, SOD and CAT activities, and Bcl-2, Bax, NF-κB, and caspase-3 expression levels were analyzed from the obtained cell lysates. As a result, according to the findings obtained, IMA and MDA levels decreased in the A549 cancer cell line, while GSH levels and SOD and CAT activity increased. It was determined that the application of apocynin to A549 cells significantly reduced cell viability and directed the cells to apoptosis, increased Bax, NF-κB, and caspase-3 expression, and decreased Bcl-2 expressions. Since all of the data obtained were not found in the literature about the use of apocynin in the A549, the study conducted is pioneering. Our study demonstrates the potential of apocynin for cancer therapy possibly targeting the apoptotic pathway.

Graphical Abstract

Synthesis and evaluation of esters obtained from phenols and phenoxyacetic acid with significant phytotoxic and cytogenotoxic activities

There is a growing demand for herbicides that are more effective than conventional ones yet less harmful to ecosystems. In light of this, this study aimed to synthesize esters from phenols and phenoxyacetic acid, using compounds with known phytotoxic potential as starting materials. Phenoxyacetic acid was first synthesized and then utilized in the synthesis of seven esters through Steglich esterification, employing N,N'-dicyclohexylcarboimide and N,N-dimethylpyridin-4-amine in the presence of phenols (thymol, vanillin, eugenol, carvacrol, guaiacol, p-cresol, and β-naphthol), yielding esters 1-7. All synthesized compounds were characterized using mass spectrometry, 1H, and 13C NMR. These compounds were tested for phytotoxicity to evaluate their effects on the germination and root development of Sorghum bicolor and Lactuca sativa seeds, and for the induction of alterations in the mitotic cycle of meristematic cells of L. sativa roots. Esters 1, 3, 4, and 5 exhibited the most significant phytotoxic activity in both L. sativa and S. bicolor. Alterations in the mitotic index and frequency of chromosomal alterations in L. sativa roots revealed the cytotoxic, genotoxic effects, and the aneugenic mode of action of the tested molecules. These findings suggest that these compounds could serve as inspiration for the synthesis of new semi-synthetic herbicides.

Exploring the effects of vanillin and divanillin on murine osteosarcoma cells: evaluation of cellular response and proteomic analysis

The objective of this study was to evaluate the antitumor properties of vanillin and divanillin in murine bone tumour cells. The action of the compounds on the cell viability of the normal (MC3T3-E1) and the tumour cell line (UMR-106) was evaluated. Action of the compounds in colony formation, migration, and production of reactive oxygen species (ROS) in tumour cells were evaluated along with proteomic analysis. Both compounds affected the cell viability of normal and tumour cell lines, being divanillin the more effective. For UMR-106, both compounds reduced the cell viability by less than 50%. Vanillin inhibited the migration process, and divanillin decreased ROS production (p < 0.05). The proteomic analysis showed that both compounds acted in the expression of proteins involved in tumour progression. Our results suggest that vanillin and divanillin are effective drugs against murine bone tumour cells. They can be a promising alternative for the adjuvant treatment of bone cancer.

Belamcanda chinensis extract inhibits non-small cell lung cancer proliferation and induces apoptosis via inhibiting the MAPK (Ras/Raf) and Akt pathways

Non-small cell lung cancer (NSCLC) is associated with high mortality and morbidity rates. Despite major progress of treatment of NSCLC over the past few decades, the prognosis of advanced NSCLC is poor, with 5-year survival rates ranging from 2 % to 13 %. Belamcanda chinensis is a traditional Chinese medicine used to promote blood circulation, reduce swelling, heal ulcers, disperse lumps and tumors, and resolve blood stasis. In the present study, the anti-proliferative and pro-apoptotic effects and potential mechanisms of action of Belamcanda chinensis extract (BCE) in SPC-A1 and NCI-H460 NSCLC cells were investigated using MTS, flow cytometry, and western blotting. Also, xenograft model in vivo was established to investigate the anti-NSCLC effects of BCE. The compounds in BCE were quantified using gas chromatography-mass spectrometry (GC-MS). Twenty compounds were found in BCE, and BCE induced cell cycle arrest significantly inhibited the proliferation of NSCLC. Furthermore, BCE was found to induce Cyto C release and the activation of Caspase-3, -8, -9, PARP, ultimately inducing apoptosis in NSCLC cells through both exogenous and endogenous apoptotic pathways (the mitochondrial pathway). BCE also blocked the MAPK (Ras/Raf) and Akt signaling pathways, significantly downregulating the expression of Ras, Raf, Erk1/2, p-Erk1/2, Akt, and p-Akt proteins. Furthermore, BCE significantly inhibited the growth of NSCLC cells SPC-A1 in nude mice and downregulated Ras, Raf, Akt, and p-Akt expression in vivo. The antitumor effects of BCE suggest its potential clinical application in patients with NSCLC, especially in those bearing Ras or Raf mutations.

Ameliorative effects of vanillin against pentylenetetrazole-induced epilepsy and associated memory loss in mice: The role of Nrf2/HO-1/NQO1 and HMGB1/RAGE/TLR4/NFκB pathways

BACKGROUND

Epilepsy is a severe neurological disorder associated with substantial morbidity and mortality. Vanillin (Van) is a natural phenolic aldehyde with beneficial pharmacological properties. This study investigated the neuroprotective effects of Van in epilepsy and elucidated its mechanism of action.

METHODS

Swiss albino mice were divided into the following five groups: "normal group", 0.9 % saline; "pentylenetetrazole (PTZ) group", intraperitoneal administration of 35 mg/kg PTZ on alternate days up to 42 days; and "PTZ + Van 20", "PTZ + Van 40", and "PTZ + sodium valproate (Val)" groups received PTZ injections in conjunction withVan 20 mg, Van 40 mg/kg, and Val 300 mg/kg, respectively. Behavioural tests and hippocampal histopathological analysis were performed in all groups. The Nrf2/HO-1/NQO1 and HMGB1/RAGE/TLR4/NFκB pathways, oxidative stress, neuro-inflammation, and apoptotic markers were analysed. Furthermore, brain acetylcholinesterase (AChE) activity and levels of dopamine (DA), gamma-aminobutyric acid GABA, and serotonin 5-HT were assessed.

RESULTS

Van prolonged seizure manifestations and improved electroencephalogram (EEG)criteriain conjunction with 100 mg/kg PTZ once daily. Van administration increased Nrf2/HO-1/NQO1 levels, with subsequent attenuation of malondialdehyde (MDA) and nitric oxide (NO) levels with elevated glutathione (GSH) levels and intensified superoxide dismutase (SOD) and catalase activities. Van reduced the gene and protein expression of HMGB1/RAGE/TLR4/NFκB and decreased the levels of inflammatory and apoptotic markers. In addition, Van reduced AChE activity, and elevated glial fibrillary acidic proteins (GFAP) increased neurotransmitter and brain-derived neurotrophic factors (BDNF).

CONCLUSION

By increasing Nrf2/HO-1/NQO1 levels and downregulating the HMGB1/RAGE/TLR4/ NFκB pathway, Van offered protection in PTZ-kindled mice with subsequent attenuation in lipid peroxidation, upregulation in antioxidant enzyme activities, and reduction in inflammation and apoptosis.

NADPH Oxidases: From Molecular Mechanisms to Current Inhibitors

NADPH oxidases (NOXs) form a family of electron-transporting membrane enzymes whose main function is reactive oxygen species (ROS) generation. Strong evidence suggests that ROS produced by NOX enzymes are major contributors to oxidative damage under pathologic conditions. Therefore, blocking the undesirable actions of these enzymes is a therapeutic strategy for treating various pathological disorders, such as cardiovascular diseases, inflammation, and cancer. To date, identification of selective NOX inhibitors is quite challenging, precluding a pharmacologic demonstration of NOX as therapeutic targets in vivo. The aim of this Perspective is to furnish an updated outlook about the small-molecule NOX inhibitors described over the last two decades. Structures, activities, and in vitro/in vivo specificity are discussed, as well as the main biological assays used.

Apocynin-loaded PLGA nanomedicine tailored with galactosylated chitosan intrigue asialoglycoprotein receptor in hepatic carcinoma: Prospective targeted therapy

Nature serves as a priceless source for phytomedicines to treat different types of cancer, including hepatocellular carcinoma (HCC). Apocynin (APO), an anti-cancer phytomedicine, is a particular nicotinamide adenine dinucleotide phosphate-oxidase (NADPH-oxidase) inhibitor, which has recently dawned for its multilateral pharmacological activities. As far as we are aware, no investigation has been carried out yet to develop a targeted-nanostructured delivery system of APO to HCC. Consequently, chitosan derivative with galactose groups namely; galactosylated chitosan (GC), particularly recognized by the asialoglycoprotein receptor (ASGR), was synthesized and its chemical structure was thoroughly characterized by substantial techniques. Afterwards, GC-coated nanoplatform for hepatocyte attachment "APO-loaded galactosylated chitosan-coated poly(d,l-lactide-co-glycolide) nanoparticles (APO-loaded GC-coated PLGA NPs)" was developed. The prosperous APO-loaded GC-coated PLGA NPs would be comprehensively appraised through extensive investigations. Their solid state characterization using Fourier transform-infrared spectroscopy, powder X-ray diffraction, and differential scanning calorimetry proved APO's encapsulation in the polymeric matrix. Transmission electron microscopy imaging of the investigated NPs highlighted their spherical architecture with a nanosized range and a characteristic halo-like appearance traceable to the GC coating of the NPs' surface. Saliently, the results of in vitro cytotoxicity screening revealed the spectacular anti-cancer efficacy of APO-loaded GC-coated PLGA NPs formula against the HepG2 cell line. Moreover, the fluorescence microscope disclosed the distinguished cellular uptake of such formula via ASGPR mediated endocytosis. Inclusively, a multifunctional nano-phytomedicine delivery system with a promising active hepatocyte-targeting, effective uptake into HepG2 cells, and sustained drug release pattern was successfully developed.

Chemical synthesis of a reported p47phox/p22phox inhibitor and characterization of its instability and irreproducible activity

The nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2) multi-subunit complex is a highly abundant and central source of reactive oxygen species. NOX2 is a key enzyme of the innate immune system involved in antibacterial response, but excessive NOX2 activity is involved in oxidative stress and inflammation in many diseases. Inhibition of NOX2 has great potential as a therapeutic strategy. An intriguing pharmacological approach for inhibiting NOX2 is to target the p47phox subunit and thereby block the protein-protein interaction with p22phox, whereby assembling and activation of NOX2 is prevented. However, the shallow binding pocket of p47phox makes it difficult to develop drug-like p47phox/p22phox inhibitors. Recently, the small molecule LMH001 was reported to inhibit the p47phox/p22phox interaction, reduce endothelial NOX2 activity, and protect mice from angiotensin II-induced vascular oxidative stress. These noteworthy results could have significant impact on the field of NOX2 pharmacology, as specific and efficient inhibitors are scarce. Here, we synthesized and tested LMH001 to have it available as a positive control. We established a robust synthetic route for providing LMH001, but subsequently we experienced that LMH001 is chemically unstable in aqueous buffer. In addition, neither LMH001 nor its breakdown products were able to inhibit the p47phox/p22phox interaction in a non-cellular fluorescence polarization assay. However, LHM001 was a weak inhibitor of NOX2 in a functional cell assay, but with same low potency as one of its breakdown products. These findings question the activity and suggested mechanism of LMH001 and constitute important information for other researchers interested in chemical probes for studying NOX2 biology.

Induced circular dichroism as a tool to monitor the displacement of ligands between albumins

The induction of chirality in a ligand can be a powerful analytical tool for studying protein-ligand interactions. Here, we advanced by applying the technique to monitor the inversion of the induced circular dichroism (ICD) spectrum when ligands move between human and bovine serum albumin proteins (HSA and BSA). ICD experiments were performed using dimers of methyl vanillate (DVT) and vanillin (DVN). The sign and spectra shape were dependent on the albumin type. DVN presented a positive maximum in 312 nm when complexed with HSA and a negative one in BSA. It was possible to induce and follow the time-dependent displacement of the ligand from BSA (2.2 × 10⁶ M^-1) to HSA (6.6 × 10⁵ M^-1) via ICD inversion. The Molecular Mechanics Generalized Born Surface Area approach was used to calculate the binding free energy of the conformers, and a dissociation pathway for each system was proposed using Umbrella Sampling calculations. Four energy minima dihedral angle conformers were identified, and the corresponding CD spectra were calculated using the quantum chemistry approach. Then, weighted spectra for the conformationally accessible conformers were obtained based on each conformer's Boltzmann probability distribution. In conclusion, the methodology described in the manuscript might be helpful in monitoring the movement of ligands between proteins that they bind.

Pyrido [1,2-a] Pyrimidinone Mesoionic Compounds Containing Vanillin Moiety: Design, Synthesis, Antibacterial Activity, and Mechanism

Xanthomonas oryzae pv. oryzicola (Xoo) is a plant pathogen responsible for rice bacterial blight disease that remains challenging for prevention and cure. To discover innovative and extremely potent antibacterial agents, vanillin moiety was introduced to develop a series of novel mesoionic derivatives. Compound 15 demonstrated excellent in vitro antibacterial activity against Xoo, with a 50% effective concentration value (EC₅₀) of 27.5 μg/mL, which was superior to that of the positive control agent thiodiazole copper (97.1 μg/mL) and comparable to that of compound "A11" (17.4 μg/mL). The greenhouse pot experiment also revealed that compound 15 had 38.5% curative and 36.8% protective efficacy against rice bacterial leaf blight in vivo at 100 μg/mL, which was higher than those of thiodiazole copper (31.2 and 32.6%, respectively) and compound "A11" (29.6 and 33.2%, respectively). Compound 15 enhanced the activities of related defense enzymes, increased chlorophyll content, and promoted the resistance of rice to bacterial infection by modulating the photosynthetic pathway. This study provides a basis for the subsequent structural modification and mechanism research of mesoionic derivatives.

The dimerization of methyl vanillate improves its effect against breast cancer cells via pro-oxidant effect

Phenolic phytochemicals are a group of organic compounds with potent antioxidant features but can also act as powerful pro-oxidants. These characteristics are effective in reducing metastatic potential in cancer cells, and this effect has been associated with reactive oxygen species (ROS). Methyl vanillate (MV) and its dimer, methyl divanillate (DMV), are potent antioxidants. In the present study, we investigated the effects of MV and DMV on breast cancer cell lines MCF-7 and MDA-MB-231 and compared the results using the non-tumor cell line HB4a. Our results indicated that the compounds performed a pro-oxidant action, increasing the generation of ROS. DMV decreased the viability cell, showing a higher apoptotic effect and inhibition of proliferation than MV on both cell lines, with significant differences between groups (p < 0.05). Some modulation of NOX4, NOX5, and DUOX were observed, but the results did not correlate with the intracellular production of ROS. The dimer showed more effectivity and pro-oxidant effect than MV, impacting cell line MCF-7 in higher extension than MDA-MB-231. In conclusion, and corroborating with reported works, the dimerization of natural phenolic compounds was associated with improved beneficial biological effects as a potential cytotoxic agent to tumor cells.

Pharmacology of apocynin: a natural acetophenone

Apocynin is a naturally occurring acetophenone, found in the roots of Apocynum cannabinum and Picrorhiza kurroa. Various chemical and pharmaceutical modifications have been carried out to enhance the absorption and duration of action of apocynin, like, formulation of chitosan-based apocynin-loaded solid lipid nanoparticles, chitosan-oligosaccharide based nanoparticles, and biodegradable polyanhydride nanoparticles. Apocynin has been subjected to a wide range of experimental screening and has proved to be useful for amelioration of a variety of disorders, like diabetic complications, neurodegeneration, cardiovascular disorders, lung cancer, hepatocellular cancer, pancreatic cancer, and pheochromocytoma. Apocynin has been primarily reported as an NADPH oxidase (NOX) inhibitor and prevents translocation of its p47^phox subunit to the plasma membrane, observed in neurodegeneration and hypertension. However, recent studies highlight its off-target effects that it is able to function as a scavenger of non-radical oxidant species, which is relevant for its activity against NOX 4 mediated production of hydrogen peroxide. Additionally, apocynin has shown inhibition of eNOS-dependent superoxide production in diabetic cardiomyopathy, reduction of NLRP3 activation and TGFβ/Smad signaling in diabetic nephropathy, diminished VEGF expression and decreased retinal NF-κB activation in diabetic retinopathy, inhibition of P38/MAPK/Caspase3 pathway in pheochromocytoma, inhibition of AKT-GSK3β and ERK1/2 pathways in pancreatic cancer, and decreased FAK/PI3K/Akt signaling in hepatocellular cancer. This review aims to discuss the pharmacokinetics and mechanisms of the pharmacological actions of apocynin.

Vanillin: a review on the therapeutic prospects of a popular flavouring molecule

Abstract

Graphic abstract

Vanillin protects lipopolysaccharide-induced acute lung injury by inhibiting ERK1/2, p38 and NF-κB pathway

Aim: Thus far, the anti-inflammatory effect of vanillin in acute lung injury (ALI) has not been studied. This study aimed to investigate the effect of vanillin in lipopolysaccharide (LPS)-induced ALI. Results & methodology: Our study detected the anti-inflammatory effects of vanillin by ELISA and western blot, respectively. Pretreatment of mice with vanillin significantly attenuated LPS-stimulated lung histopathological changes, myeloperoxidase activity and expression levels of proinflammatory cytokines by inhibiting the phosphorylation activities of ERK1/2, p38, AKT and NF-κB p65. In addition, vanillin inhibited LPS-induced TNF-α and IL-6 expression in RAW264.7 cells via ERK1/2, p38 and NF-κB signaling. Conclusion: Vanillin can inhibit macrophage activation and lung inflammation, which suggests new insights for clinical treatment of ALI.

One-Pot Efficient Catalytic Oxidation for Bio-Vanillin Preparation and Carbon Isotope Analysis

Vanillin (4-hydroxy-3-methoxybenzaldehyde) is one of the most widely used food spices. Aimed at bio-vanillin green production, the natural materials were directly catalytically oxidized efficiently in one pot under low O₂ pressure (0.035 MPa) in the presence of a non-noble metal oxidation combined catalyst (NiCo₂O₄/SiO₂ nanoparticles), which showed remarkable advantages of a short synthetic route and less industrial waste. The catalytic system showed good universality to many natural substrates with nearly 100% conversion and 86.3% bio-vanillin yield. More importantly, carbon isotope ratio investigations were employed to verify the origin of the organic matter. One hundred percent ¹⁴C content of the obtained vanillin was detected, which indicated that it was an efficient method to distinguish the vanillin from biomass or fossil materials. Furthermore, the ¹³C isotope examination showed effective distinguishing ability for the vanillin from a particular biomass source. The C isotope detection provides an effective method for commercial vanillin identification.

Depigmentation and Anti-aging Treatment by Natural Molecules

Natural molecules are becoming more accepted choices as cosmetic agents, many products in the market today claim to include natural components. Plants include many substances that could be of a value in the whitening of the skin and working as anti-aging agents. A wide range of articles related to natural skin whitening and anti-aging agents have been reviewed. Many plant-derived and natural molecules have shown to affect melanin synthesis by different mechanisms, examples include Arbutin, Ramulus mori extract, Licorice extract, Glabridin, Liquiritin, Kojic acid, Methyl gentisate, Aloesin, Azelaic acid, Vitamin C, Thioctic acid, Soya bean extracts, Niacinamide, α and β-hydroxy acids, Lactic acid, Chamomile extract, and Ellagic acid. Some of the widely used natural anti-aging products as natural antioxidants, collagen, hyaluronic acid, and coenzyme Q can counteract the effects of reactive oxygen species in skin cells and have anti-aging properties on the skin. It was concluded that many natural products including antioxidants can prevent UV-induced skin damage and have whitening and anti-aging effects. It is very important to develop and stabilize appropriate methods for the evaluation of the whitening and anti-aging capacity of natural products and their exact mechanism of action to ensure real efficacy based on evidence-based studies. The attention should be oriented on the formulations and the development of an appropriate vehicle to ensure suitable absorption of these natural products in addition to evaluating the suitable concentration of these molecules required having the desired effects without causing harmful side effects.

Apocynin prevents GM-CSF-induced-ERK1/2 activation and -neutrophil survival independently of its inhibitory effect on the phagocyte NADPH oxidase NOX2

Neutrophils are key cells in innate immunity and inflammation. Granulocyte-macrophage colony-stimulating factor (GM-CSF) is known to enhance many neutrophil functions such as reactive oxygen species (ROS) production, degranulation and cell survival via the activation of the ERK1/2 pathway. ERK1/2 pathway activation is redox sensitive and could be modulated by ROS. In order to investigate whether NADPH oxidase NOX2-derived ROS could contribute to GM-CSF-induced ERK1/2 phosphorylation, we tested the effect of two selective NOX2 inhibitors, diphenylene iodonium (DPI) and apocynin. Results showed that, while both DPI and apocynin strongly inhibited neutrophil ROS production, only apocynin, but not DPI, inhibited GM-CSF-induced ERK1/2 phosphorylation, suggesting that ROS are not involved in this process. Apocynin did not affect GM-CSF-induced p38MAPKinase phosphorylation, another redox sensitive kinase. Interestingly, apocynin inhibited GM-CSF-induced MEK1/2 and AKT phosphorylation without affecting fMLF-induced phosphorylation of these proteins. GM-CSF is known to inhibit neutrophils apoptosis and to promote cell survival via the AKT-ERK1/2 pathway. In this regard, we found that apocynin also inhibited GM-CSF-induced anti-apoptotic effect in neutrophils. These results suggest that NADPH oxidase NOX2-derived ROS are not involved in GM-CSF-induced ERK1/2 phosphorylation and that apocynin inhibits GM-CSF-induced ERK1/2 phosphorylation pathway independently of its inhibitory action on NADPH oxidase NOX2. Thus, apocynin can exert an anti-inflammatory effect not only by limiting neutrophil ROS production but also by decreasing neutrophil survival at inflammatory site.

Targeting cellular microtubule by phytochemical apocynin exhibits autophagy-mediated apoptosis to inhibit lung carcinoma progression and tumorigenesis

BACKGROUND

Lung cancer is the leading cause of cancer-related deaths worldwide. Several targets have been identified for lung cancer therapy, amongst which 'Microtubule' and its dynamics are the most widely studied and used in therapy. Tubulin-microtubule polymer dynamics are highly sought after targets in the field of anti-cancer drug designing. Natural compounds are important sources for developing anticancer therapeutics owing to their efficacy and lower cytotoxicity. Evidence suggested that therapeutic targeting of microtubule by natural compounds is amongst the most widely used interventions in numerous cancer therapies including lung cancer.

PURPOSE

To determine the efficacy of apocynin (a natural compound) in suppressing the progression of lung carcinoma both in vitro and in vivo, along with the identification of targets and the underlying mechanism for developing a novel therapeutic approach.

METHODS

We have demonstrated themicrotubule depolymerizing role of apocynin by established protocols in cellular and cell-free system. The efficacy of apocynin to inhibit lung carcinoma progression was studied on A549 cells.The tumoricidal ability of apocynin was studied in BALB/c mice model as well.Mice were classified into 4 groups namely-group II mice as tumor control; group III-IV mice asalso tumor-induced but treated with differential apocynin doses whereas group I mice were kept as normal.

RESULTS

Apocynin, showed selective cytotoxicity towards lung cancer cells rather than normal lung fibroblast cells. Apocynin inhibited oncogenic properties including growth, proliferation (p < 0.05), colony formation (p < 0.05), invasion (p < 0.05) and spheroid formation (p < 0.05) in lung cancer cells. Apart from other established properties, apocynin was found to be a novel and potent component to bind with tubulin and depolymerize cellular microtubule network. Apocynin mediated cellular microtubule depolymerization was the driving mechanism to trigger autophagy-mediated apoptotic cell death (p < 0.05) which in turn retarded lung cancer progression. Furthermore, apocynin showed tumoricidal characteristics to inhibit lung tumorigenesis in mice as well.

CONCLUSION

Targeting tubulin-microtubule equilibrium with apocynin could be the key regulator to catastrophe cellular catabolic processes to mitigate lung carcinoma. Thus, apocynin could be a potential therapeutic agent for lung cancer treatment.

First Discovery of Novel Pyrido[1,2-a]pyrimidinone Mesoionic Compounds as Antibacterial Agents

Plant bacterial diseases cause tremendous decreases in crop yield and quality, and there is a lack of highly effective and low-risk antibacterial agents. A series of novel pyrido[1,2-a]pyrimidinone mesoionic compounds containing vanillin moieties were synthesized, and the application of these mesoionic compounds as plant antibacterial agents was reported here for the first time. The bioassay results revealed that the mesoionic compounds had good antibacterial activity. Of these compounds, compound 11 showed excellent in vitro activity against Xanthomonas oryzae pv. oryzae, with an EC₅₀ value of 1.1 μg/mL, which was substantially better than that of bismerthiazol (92.7 μg/mL) and thiodiazole copper (105.4 μg/mL). Moreover, greenhouse condition trials indicated that the protective and curative activities of compound 11 against rice bacterial leaf blight were 75.12 and 72.04%, respectively, which were better than those of bismerthiazol (62.24 and 50.83%, respectively) and thiodiazole copper (53.35 and 65.04%, respectively). These results provide a basis for the application of mesoionic vanillin moieties as new antibacterial agents.

Methyl divanillate: redox properties and binding affinity with albumin of an antioxidant and potential NADPH oxidase inhibitor

Vanillic acid is a widely used food additive (flavouring agent, JECFA number: 959) with many reported beneficial biological effects. The same is true for its ester derivative (methyl vanillate, JECFA number: 159). Based on the increasing evidence that diapocynin, the dimer of apocynin (NADPH oxidase inhibitor), has some improved pharmacological properties compared to its monomer, here the dimer of methyl vanillate (MV), i.e., methyl divanillate (dimer of methyl vanillate, DMV) was synthesized and studied in the context of its redox properties and binding affinity with human serum albumin (HSA). We found that the antioxidant potency of DMV was significantly increased compared to MV. In this regard, the reduction of 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical by DMV was 30-fold more effective compared to MV. Ferric ion reduction was 4-fold higher and peroxyl radical reduction was 2.7-fold higher. The interaction with HSA was significantly improved (Stern–Vomer constants, 3.8 × 10⁵ mol⁻¹ L and 2.3 × 10⁴ mol⁻¹ L, for DMV and MV, respectively). The complexation between DMV and HSA was also evidenced by induced circular dichroism (ICD) signal generation in the former due to its fixation in the asymmetric protein pocket. Density-functional calculations (TD-DFT) showed that the ICD spectrum was related to a DMV conformation bearing a dihedral angle of approximately −60°. Similar dihedral angles were obtained in the lowest and most populated DMV cluster poses obtained by molecular docking simulations. The computational studies and experimental displacement studies revealed that DMV binds preferentially at site I. In conclusion, besides being a powerful antioxidant, DMV is also a strong ligand of HSA. This is the first study on the chemical and biophysical properties of DMV, a compound with potential beneficial biological effects.

Methyl divanillate, a derivative of the vanillic acid (flavouring agent, JECFA number: 959) with promising beneficial biological effects.

UV cell stress induces oxidative cyclization of a protective reagent for DNA damage reduction in skin explants

UV irradiation is a major driver of DNA damage and ultimately skin cancer. UV exposure leads to persistent radicals that generate ROS over prolonged periods of time. Toward the goal of developing long-lasting antioxidants that can penetrate skin, we have designed a ROS-initiated protective (RIP) reagent that, upon reaction with ROS (antioxidant activity), self-cyclizes and then releases the natural product apocynin. Apocynin is a known antioxidant and inhibitor of NOX oxidase enzymes. A key phenol on the compound 1 controls ROS-initiated cyclization and makes 1 responsive to ROS with a EC50 comparable to common antioxidants in an ABTS assay. In an in vitro DNA nicking assay, the RIP reagent prevented DNA strand breaks. In cell-based assays, the reagent was not cytotoxic, apocynin was released only in cells treated with UVR, reduced UVR-induced cell death, and lowered DNA lesion formation. Finally, topical treatment of human skin explants with the RIP reagent reduced UV-induced DNA damage as monitored by quantification of cyclobutane dimer formation and DNA repair signaling via TP53. The reagent was more effective than administration of a catalase antioxidant on skin explants. This chemistry platform will expand the types of ROS-activated motifs and enable inhibitor release for potential use as a long-acting sunscreen.

Natural Antioxidants: Multiple Mechanisms to Protect Skin From Solar Radiation

Human skin exposed to solar ultraviolet radiation (UVR) results in a dramatic increase in the production of reactive oxygen species (ROS). The sudden increase in ROS shifts the natural balance toward a pro-oxidative state, resulting in oxidative stress. The detrimental effects of oxidative stress occur through multiple mechanisms that involve alterations to proteins and lipids, induction of inflammation, immunosuppression, DNA damage, and activation of signaling pathways that affect gene transcription, cell cycle, proliferation, and apoptosis. All of these alterations promote carcinogenesis and therefore, regulation of ROS levels is critical to the maintenance of normal skin homeostasis. Several botanical products have been found to exhibit potent antioxidant capacity and the ability to counteract UV-induced insults to the skin. These natural products exert their beneficial effects through multiple pathways, including some known to be negatively affected by solar UVR. Aging of the skin is also accelerated by UVR exposure, in particular UVA rays that penetrate deep into the epidermis and the dermis where it causes the degradation of collagen and elastin fibers via oxidative stress and activation of matrix metalloproteinases (MMPs). Because natural compounds are capable of attenuating some of the UV-induced aging effects in the skin, increased attention has been generated in the area of cosmetic sciences. The focus of this review is to cover the most prominent phytoproducts with potential to mitigate the deleterious effects of solar UVR and suitability for use in topical application.

Oral Administration of Vanillin Improves Imiquimod-Induced Psoriatic Skin Inflammation in Mice

Vanillin is one of the most widely used flavoring products worldwide. Psoriasis is a chronic inflammatory skin disorder. The interleukin-23 (IL-23)/interleukin-17 (IL-17) axis plays a critical role in psoriasis. Here, we analyzed the effect of vanillin on imiquimod (IMQ)-induced psoriatic skin inflammation in mice. Mice were treated topically with IMQ on the back skin and orally with various amounts of vanillin for 7 consecutive days. Vanillin significantly improved IMQ-induced histopathological changes of skin in a dose-dependent manner. The thickness and number of cell layers of epidermis were reduced by 29 ± 14.4 and 27.8 ± 11%, respectively, in mice given 100 mg/kg of vanillin. A microarray showed that a total of 9042 IMQ-upregulated genes were downregulated by vanillin, and the biological pathways involved in the immune system and metabolism were significantly altered by vanillin. The upregulated expressions of IL-23, IL-17A, and IL-17F genes were suppressed by vanillin, with fold changes of -3.07 ± 0.08, -2.06 ± 0.21, and -1.62 ± 0.21, respectively. Moreover, vanillin significantly decreased both the amounts of IL-17A and IL-23 and the infiltration of immune cells in the skin tissues of IMQ-treated mice. In conclusion, our findings suggested that vanillin was an effective bioactive compound against psoriatic skin inflammation. Moreover, the downregulation of IL-23 and IL-17 expression suggested that vanillin was a novel regulator of the IL-23/IL-17 axis.

Creating Oxidase-Peroxidase Fusion Enzymes as a Toolbox for Cascade Reactions

A set of bifunctional oxidase-peroxidases has been prepared by fusing four distinct oxidases to a peroxidase. Although such fusion enzymes have not been observed in nature, they could be expressed and purified in good yields. Characterization revealed that the artificial enzymes retained the capability to bind the two required cofactors and were catalytically active as oxidase and peroxidase. Peroxidase fusions of alditol oxidase and chitooligosaccharide oxidase could be used for the selective detection of xylitol and cellobiose with a detection limit in the low-micromolar range. The peroxidase fusions of eugenol oxidase and 5-hydroxymethylfurfural oxidase could be used for dioxygen-driven, one-pot, two-step cascade reactions to convert vanillyl alcohol into divanillin and eugenol into lignin oligomers. The designed oxidase-peroxidase fusions represent attractive biocatalysts that allow efficient biocatalytic cascade oxidations that only require molecular oxygen as an oxidant.

Facile Synthesis of Novel Vanillin Derivatives Incorporating a Bis(2-hydroxyethyl)dithhioacetal Moiety as Antiviral Agents

A series of vanillin derivatives incorporating a bis(2-hydroxyethyl)dithioacetal moiety was designed and synthesized via a facile method. A plausible reaction pathway was proposed and verified by computational studies. Bioassay results demonstrated that target compounds possessed good to excellent activities against potato virus Y (PVY) and cucumber mosaic virus (CMV), of which, compound 6f incorporating a bis(2-hydroxyethyl)dithioacetal moiety, exhibited the best curative and protection activities against PVY and CMV in vivo, with 50% effective concentration values of 217.6, 205.7 μg/mL and 206.3, 186.2 μg/mL, respectively, better than those of ribavirin (848.0, 808.1 μg/mL and 858.2, 766.5 μg/mL, respectively), dufulin (462.6, 454.8 μg/mL and 471.2, 465.4 μg/mL, respectively), and ningnanmycin (440.5, 425.3 μg/mL and 426.1, 405.3 μg/mL, respectively). Current studies provide support for the application of vanillin derivatives incorporating bis(2-hydroxyethyl)dithioacetal as new antiviral agents.

Induction of axial chirality in divanillin by interaction with bovine serum albumin

Vanillin is a plant secondary metabolite and has numerous beneficial health applications. Divanillin is the homodimer of vanillin and used as a taste enhancer compound and also a promissory anticancer drug. Here, divanillin was synthesized and studied in the context of its interaction with bovine serum albumin (BSA). We found that divanillin acquires axial chirality when complexed with BSA. This chiroptical property was demonstrated by a strong induced circular dichroism (ICD) signal. In agreement with this finding, the association constant between BSA and divanillin (3.3 x 105 mol-1L) was higher compared to its precursor vanillin (7.3 x 104 mol-1L). The ICD signal was used for evaluation of the association constant, demonstration of the reversibility of the interaction and determination of the binding site, revealing that divanillin has preference for Sudlow's site I in BSA. This property was confirmed by displacement of the fluorescent markers warfarin (site I) and dansyl-L-proline (site II). Molecular docking simulation confirmed the higher affinity of divanillin to site I. The highest scored conformation obtained by docking (dihedral angle 242°) was used for calculation of the circular dichroism spectrum of divanillin using Time-Dependent Density Functional Theory (TDDFT). The theoretical spectrum showed good similarity with the experimental ICD. In summary, we have demonstrated that by interacting with the chiral cavities in BSA, divanillin became a atropos biphenyl, i.e., the free rotation around the single bound that links the aromatic rings was impeded. This phenomenon can be explained considering the interactions of divanillin with amino acid residues in the binding site of the protein. This chiroptical property can be very useful for studying the effects of divanillin in biological systems. Considering the potential pharmacological application of divanillin, these findings will be helpful for researchers interested in the pharmacological properties of this compound.

Influence of Dimerization of Apocynin on Its Effects in Experimental Colitis

Apocynin has been widely used as an inhibitor of the nicotinamide adenine dinucleotide phosphate oxidase (NADPH-oxidase) system and shows promise as an anti-inflammatory drug. Diapocynin, the dimeric product generated by the oxidation of apocynin in the presence of myeloperoxidase (MPO), is supposed to be its active form. In this study, diapocynin has been chemically synthesized and its activity on several inflammatory mediators in LPS-stimulated RAW 264.7 macrophages and its anti-inflammatory effect on ulcerative colitis induced by dextran sodium sulfate (DSS) in mice analyzed. We found that diapocynin showed higher inhibitory activity than apocynin. The dimer reduced ROS production, TNF-α, IL-6, and IL-1β levels and inhibited iNOS and COX-2 expression as well as decreased NO and PGE₂ production induced in LPS-stimulated RAW 264.7 cells. The anti-inflammatory molecular mechanism of diapocynin was associated with the suppression of NF-κB activation. However, these results were not paralleled by in vivo studies. Oral administration of apocynin and diapocynin (100 mg/kg) three times a week exhibited similar protections against experimental inflammatory bowel disease induced by DSS; therefore, apocynin should not be considered a prodrug. However, it should be taken into account that the dimer is more potent because its dose (0.3 mmol/kg) is half that of apocynin.