Finding more active antioxidants and cancer chemoprevention agents by elongating the conjugated links of resveratrol

Compounds from Agathis dammara exert hypoglycaemic activity by enhancing glucose uptake: lignans, terpenes and others

In this study, two new kaurane diterpenes (16, 17), together with 12 lignans (1-12), a triterpene (15), and two other compounds (13, 14) were isolated from the woods of Agathis dammara. The structure of the new compound was determined by HR ESIMS and 1D/2D NMR spectroscopy, and its absolute configuration was determined by electronic circular dichroism (ECD) exciton chirality method. Compounds 5, 11, 14 exhibit significant hypoglycaemic activity in zebrafish, and their mechanism of action is to enhance glucose uptake in zebrafish.

Cardiovascular risk of dietary trimethylamine oxide precursors and the therapeutic potential of resveratrol and its derivatives

Overall diet, lifestyle choices, genetic predisposition, and other underlying health conditions may contribute to higher trimethylamine N-oxide (TMAO) levels and increased cardiovascular risk. This review explores the potential therapeutic ability of RSV to protect against cardiovascular diseases (CVD) and affect TMAO levels. This review considers recent studies on the association of TMAO with CVD. It also examines the sources, mechanisms, and metabolism of TMAO along with TMAO-induced cardiovascular events. Plant polyphenolic compounds, including resveratrol (RSV), and their cardioprotective mechanism of regulating TMAO levels and modifying gut microbiota are also discussed here. RSV's salient features and bioactive properties in reducing CVD have been evaluated. The close relationship between TMAO and CVD is clearly understood from currently available data, making it a potent biomarker for CVD. Precise investigation, including clinical trials, must be performed to understand RSV's mechanism, dose, effects, and derivatives as a cardioprotectant agent.

Resveratrol and Its Analogue 4,4′-Dihydroxy-trans-stilbene Inhibit Lewis Lung Carcinoma Growth In Vivo through Apoptosis, Autophagy and Modulation of the Tumour Microenvironment in a Murine Model

Lung cancer is the most prevalent cancer worldwide. Despite advances in surgery and immune-chemotherapy, the therapeutic outcome remains poor. In recent years, the anticancer properties of natural compounds, along with their low toxic side effects, have attracted the interest of researchers. Resveratrol (RSV) and many of its derivatives received particular attention for their beneficial bioactivity. Here we studied the activity of RSV and of its analogue 4,4′-dihydroxystilbene (DHS) in C57BL/6J mice bearing cancers resulting from Lung Lewis Carcinoma (LLC) cell implantation, considering tumour mass weight, angiogenesis, cell proliferation and death, autophagy, as well as characterization of their immune microenvironment, including infiltrating cancer-associated fibroblasts (CAFs). C57BL/6J mice started treatment with RSV or DHS, solubilised in drinking water, one week before LLC implantation, and continued for 21 days, at the end of which they were sacrificed, and the tumour masses collected. Histology was performed according to standard procedures; angiogenesis, cell proliferation and death, autophagy, infiltrating-immune cells, macrophages and fibroblasts were assessed by immunodetection assays. Both stilbenic compounds were able to contrast the tumour growth by increasing apoptosis and autophagy in LLC tumour masses. Additionally, they contrasted the tumour-permissive microenvironment by limiting the infiltration of tumour-associated immune-cells and, more importantly, by counteracting CAF maturation. Therefore, both stilbenes could be employed to synergise with conventional oncotherapies to limit the contribution of stromal cells in tumour growth.

Separation and Identification of Resveratrol Butyrate Ester Complexes and Their Bioactivity in HepG2 Cell Models

Resveratrol butyrate ester (RBE) complexes have demonstrated higher antioxidant capacity and anti-fat accumulation activity in previous studies. In this study, silica gel, high-performance liquid chromatography, and 1H nuclear magnetic resonance were used for separation and identification of RBE complex components. With the exception of resveratrol, five different structures of ester derivatives were separated from silica gel: 3,4′-di-O-butanoylresveratrol (ED2, 18.8%), 3-O-butanoylresveratrol (ED4, 35.7%), 4′-O-butanoylresveratrol (ED5, 4.4%), 3,5,4′-tri-O-butanoylresveratrol (ED6, 1.5%), and 3,5-di-O-butanoylresveratrol (ED7, 0.7%). Among the ester derivatives obtained, ED2 and ED4 were the main ester derivatives in the RBE complex. Thus, the cellular antioxidant activities of the RBE mixture, ED2, and ED4 were evaluated. Results showed that the antioxidant capacity of ED2 and ED4 was higher than that of the RBE mixture, demonstrating that the number and position of butyrate esterification sites are related to cell survival rate and antioxidant capacity. This study is the first to report the successful isolation, structural identification, and cellular biological antioxidant activity of RBE complex derivatives, which are key characteristics for the potential practical application of RBE complexes.

Design and Synthesis of π-Extended Resveratrol Analogues and In Vitro Antioxidant and Anti-Inflammatory Activity Evaluation

The research on resveratrol (1) has been conducted intensively over a long time due to its proven antioxidant activity and disease-fighting capabilities. Many efforts have also been made to increase these biological effects. In the present study, six new extended aromatic resveratrol analogues containing naphthalene (2) and its bioisosteres quinoline (3 and 4), isoquinoline (5) quinoxaline (6) and quinazoline (7) scaffolds were designed and synthesized using an annulation strategy. The antioxidant and anti-inflammatory activities of these compounds were investigated. All compounds showed better antioxidant activity than resveratrol in ABTS assay. As for the anti-inflammatory test, 5 and 7 exhibited better activity than resveratrol. It is worth noting that nitrogen substitution on the extended aromatic resveratrol analogues has a significant impact on cell viability. Taking the antioxidant activities and NO inhibition activities into consideration, we conclude that isoquinoline analogue 5 may qualify for the further investigation of antioxidant and anti-inflammatory therapy. Furthermore, our study results suggest that in order to improve the biological activity of polyphenolic compounds, extended aromaticity and nitrogen substitution strategy could be a viable method for the design of future drug candidates.

Antiradical Properties of trans-2-(4-substituted-styryl)-thiophene

2-substituted thiophene compounds with electron donating and electron withdrawing p-phenyl substitution were synthesized and studied their radical scavenging properties using DPPH assay and DFT method. It is shown that p-hydroxy and p-amino phenyl substituted compound exhibit radical scavenging activity. From DFT and radical scavenging studies, a correlation between IC₅₀ with the bond dissociation enthalpy, proton affinity, ground state dipole moment and optical band gap of compound is found. Compounds 1-3 with electron withdrawing substituent (NO₂, CN, Cl) do not show any radical scavenging properties, whereas compounds 6-7 with electron donating substituent (OH, NH₂) show antiradical properties. Further, the antiradical activity is reduced drastically by replacing the -OH and -NH₂ with methoxy and -N-alkylating group respectively in 6 and 7. The compound with p-hydroxy phenyl substitution, exhibits stronger antiradical activity as compared to the p-amino phenyl substitution due to smaller O-H bond dissociation energy as compared to the N-H bond. From DPPH and DFT studies, it is suggested that the radical scavenging activity in 2-substituted thiophene is occurred through proton transfer mechanism. The other possible SET, SPLET mechanisms are also corroborated. Graphical Abstract Antiradical properties of trans-2-(4-substituted-styryl)-thiophene Anamika Gusain, Naresh Kumar, Jagdeep Kumar, Gunjan Pandey, Prasanta Kumar Hota.

Inhibiting NF-κB-Mediated Inflammation by Catechol-Type Diphenylbutadiene via an Intracellular Copper- and Iron-Dependent Pro-Oxidative Role

Chronic inflammation mediated by nuclear factor-κB (NF-κB) plays a crucial role in the development of cancer. As part of our continuous efforts placed on investigating anticancer mechanisms of dietary catechols, we further applied catechol-type diphenylbutadiene (3,4-DHB) as a model molecule to probe whether it inhibits inflammation by its pro-oxidative role. Employing lipopolysaccharide-stimulated RAW264.7 cells as a model of inflammation, we validated that benefiting from its catechol moiety, 3,4-DHB inhibited significantly the LPS-induced formation of NO (11.48 ± 0.39 μM) compared with the only LPS-stimulated group (31.8 ± 1.78 μM) with an inhibitory rate of 64% at 5 μM, expression of iNOS and COX-2 proteins, phosphorylation of IkB kinase and IkBα, and nuclear translocation of NF-κB. Noticeably, its inhibitory activity against the NF-κB-mediated inflammation can be obviously revised by pretreatment of the cells with dithiothreitol (a quencher of both electrophilic o-quinone and ROS), neocuproine (a specific chelating agent for copper ions), and deferoxamine (a specific chelating agent for iron ions). The above results support that depending on intracellular copper and iron ions, 3,4-DHB, a pro-electrophile, can be converted into its corresponding o-quinone electrophile together with the generation of ROS, a pro-oxidative event that mediates its inhibitory activity against NF-κB signaling and inflammation. The copper- and iron-dependent inhibition against inflammation supports that dietary catechols are probably pro-oxidative anti-inflammatory agents.

Interactions between bioactive components determine antioxidant, cytotoxic and nutrigenomic activity of cocoa powder extract

Numerous studies have shown, rather disappointingly, that isolated bioactive phytochemicals are not as biologically effective as natural plant products. Such a discrepancy may be explained by the concept of food synergy, which was verified in this research for cocoa extract versus its major components with regard to cancer chemoprevention. The evaluation embraced the relationship between redox properties evaluated in cell-free systems with the aid of free radicals scavenging method and differential pulse voltammetry, and redox associated anticarcinogenic activities (cellular antioxidant activity, cytotoxicity, nutrigenomic activity) in human colon adenocarcinoma cell line exposed to either cocoa powder extract or artificial mixtures of cocoa bioactives at matching concentrations. In contrast to expectations, our results showed that the stepwise enrichment with antioxidants caused no gradual increase in the antioxidant activity of the model mixtures; also, these model mixtures did not reach the reducing potential of cocoa in the cell-free systems or cellular model employed. Further, the biological activities examined in colon adenocarcinoma cells did not alter in a stepwise manner that could reflect the gradual changes in composition of bioactive ingredients. In conclusion, the experiments presented here showed that the growing complexity of a mixture of phytochemicals seems to create a new redox bioactive substance rather than enrich the mixture with new activities, characteristic of the compound added. It follows that no simple, predictable relationship can be expected between the chemopreventive potential and the composition of real food items containing a complicated set of non-toxic redox active ingredients. Our observations suggest that the interactions between different bioactive compounds and food matrix components are cooperating factors determining the final bioactivity of foods.

Exploring Diverse-Ring Analogues on Combretastatin A4 (CA-4) Olefin as Microtubule-Targeting Agents

Combretastatin-4 (CA-4) as a tubulin polymerization inhibitor draws extensive attentions. However, due to its weak stability of cis-olefin and poor metabolic stability, structure modifications on cis-configuration are being performed. In this work, we constructed a series of novel CA-4 analogues with linkers on olefin containing diphenylethanone, cis-locked dihydrofuran, α-substituted diphenylethanone, cyclobutane and cyclohexane on its cis-olefin. Cytotoxic activity of all analogues was measured by an SRB assay. Among them, compound 6b, a by-product in the preparation of diphenylethanone analogues, was found to be the most potent cytotoxic agents against HepG2 cells with IC₅₀ values of less than 0.5 μM. The two isomers of 6b induced cellular apoptosis tested by Annexin V-FITC and propidium iodide (PI) double staining, arrested cells in the G2/M phase by PI staining analysis, and disrupted microtubule network by immunohistochemistry study in HepG2 cells. Moreover, 6b-(E) displayed a dose-dependent inhibition effect for tubulin assembly in in vitro tubulin polymerization assay. In addition, molecular docking studies showed that two isomers of 6b could bind efficiently at colchicine binding site of tubulin similar to CA-4.

Antioxidant properties of ethenyl indole: DPPH assay and TDDFT studies

Ethenyl indole exhibits antioxidant activity in a substituent dependent manner. Ethenyls bearing strong electron withdrawing substituents show weak or no antioxidant activities, whereas ethenyls with electron donating substituents exhibit antioxidant properties comparable to vitamin E.

Duchesnea indica extract attenuates oral cancer cells metastatic potential through the inhibition of the matrix metalloproteinase-2 activity by down-regulating the MEK/ERK pathway

BACKGROUND

Duchesnea indica (Andr.) Focke, an herb in folk medicine used extensively in traditional Chinese medicine, has cytostatic properties as well as antioxidant and antimetastasis activities in various cancer cells. However, the effects and underlying mechanisms of Duchesnea indica extracts (DIEs) on human oral squamous cell carcinoma (OSCC) metastases remain unclear.

PURPOSE

In this study, we posit the hypothesis that DIE possesses antimetastatic effects on human OSCC cells.

METHODS

The effects of DIE on cell viability, motility, migration, and invasion were investigated. Gelatin zymography, Western blotting, migration and invasion assays were used to further study the underlying mechanisms involved in the antimetastatic effects of DIE in OSCC cells.

RESULTS

The results from MTT assay revealed that DIE did not affect the cell viability of OSCC cells. Moreover, DIE significantly attenuated OSCC cells' motility, migration, and invasion by reducing the MMP-2 protein expression and MMP-2 activity in a dose-dependent manner. In addition, DIE reduced the phosphorylation of both ERK1/2 and its upstream kinase but had no effect on the phosphorylation of p38 and JNK.

CONCLUSION

DIE triggers the antimetastatic activity in OSCC cells by suppressing the MMP-2 activity via the MEK/ERK signaling pathways. Therefore, these findings are promising for the use of DIE antimetastatic activity in oral cancer metastasis treatment.

Identification of Catechol-Type Diphenylbutadiene as a Tyrosinase-Activated Pro-oxidative Chemosensitizer against Melanoma A375 Cells via Glutathione S-Transferase Inhibition

Glutathione S-transferases (GSTs) play an active role in the development of drug resistance by numerous cancer cells, including melanoma cells, which is a major cause of chemotherapy failure. As part of our continuous effort to explore why dietary polyphenols bearing the catechol moiety (dietary catechols) show usually anticancer activity, catechol-type diphenylbutadiene (3,4-DHB) was selected as a model of dietary catechols to probe whether they work as pro-oxidative chemosensitizers via GST inhibition in melanoma cells. It was found that, in human melanoma A375 cells, 3,4-DHB is easily converted to its ortho-quinone via copper-containing tyrosinase-mediated two-electron oxidation along with generation of reactive oxygen species (ROS) derived from the oxidation; the resulting ortho-quinone and ROS are responsible for its ability to sensitize the cisplatin-resistant cells by inhibiting GST, followed by induction of apoptosis in an ASK1-JNK/p38 signaling cascade and mitochondria-dependent pathway. This work provides further evidence to support that dietary catechols exhibit antimelanoma activity by virtue of their tyrosinase-dependent pro-oxidative role and gives useful information for designing polyphenol-inspired GST inhibitors and sensitizers in chemotherapy against melanoma.

A promising redox cycle-based strategy for designing a catechol-type diphenylbutadiene as a potent prooxidative anti-melanoma agent

Developing anti-melanoma agents with increased activity and specificity is highly desirable due to the increasing incidence, highly metastatic malignancy, and high mortality rate of melanoma. Abnormal redox characteristics such as higher levels of tyrosinase, NAD(P)H: quinone oxidoreductase-1 (NQO1) and reactive oxygen species (ROS) observed in melanoma cells than in other cancer cells and normal cells illustrate their redox vulnerability and have opened a window for developing prooxidative anti-melanoma agents (PAAs) to target the vulnerability. However, how to design PAAs which promote selectively the ROS accumulation in melanoma cells remains a challenge. This work describes a promising redox cycle-based strategy for designing a catechol-type diphenylbutadiene as such type of PAA. This molecule is capable of constructing an efficient catalytic redox cycle with tyrosinase and NQO1 in melanoma B16F1 cells to induce selectively the ROS (mainly including hydrogen peroxide, H₂O₂) accumulation in the cells, resulting in highly selective suppression of melanoma B16F1 cells over tyrosinase-deficient HeLa and normal L-02 cells.

Targeting redox vulnerability of cancer cells by prooxidative intervention of a glutathione-activated Cu(II) pro-ionophore: Hitting three birds with one stone

Altered redox homeostasis including higher levels of copper, reduced glutathione (GSH) and reactive oxygen species (ROS) in cancer cells than in normal cells illustrates their redox vulnerability, and has opened a window for developing prooxidative anticancer agents (PAAs) to hit this status. However, how to design PAAs with high selectivity in killing cancer cells over normal cells remains a challenge. Herein we designed a 3-hydroxyflavone-inspired copper pro-ionophore (PHF) as a potent PAA based on the GSH-mediated conversion of 2,4-dinitrobenzenesulfonates to enols. Mechanistic investigation reveals that it is capable of exploiting increased levels of GSH in cancer cells to in situ release an active ionophore, 3-hydroxyflavone, inducing redox imbalance (copper accumulation, GSH depletion and ROS generation) and achieving highly selective killing of cancer cells upon specific transport of small amounts of Cu(II). To the best of our knowledge, it is the first example of Cu(II) pro-ionophore type of PAA which hits (changes) the three birds (abnormal copper, GSH and ROS levels in cancer cells) with one stone (PHF) in terms of its ability to induce preferentially redox imbalance of cancer cells by copper accumulation, GSH depletion and ROS generation.

Hybrid of Resveratrol and Glucosamine: An Approach To Enhance Antioxidant Effect against DNA Oxidation

Resveratrol exhibits various pharmacological activities, which are dependent upon phenolic hydroxyl groups. In this work, glucosamine, lipoic acid, or adamantanamine moiety was applied for attaching to ortho-position of hydroxyl group in resorcinol moiety of resveratrol (known as position-2). Antioxidant effects of the obtained hybrids were characterized using DNA oxidative systems mediated by ^•OH, Cu²⁺/glutathione (GSH), and 2,2'-azobis(2-amidinopropanehydrochloride) (AAPH), respectively. The glucosyl-appended imine and amine at position-2 of resveratrol were found to show higher inhibitory effects than other resveratrol derivatives against AAPH-induced DNA oxidation. The antioxidative effect was quantitatively expressed by stoichiometric factor ( n, the number of radical-propagation terminated by one molecule of antioxidant). The stoichiometric factors of glucosyl-appended imine and amine of resveratrol increased to 4.74 (for imine) and 4.97 (for amine), respectively, higher than that of resveratrol (3.70) and glucoside of resveratrol (3.49). It was thereby concluded that the combination of resveratrol with glucosamine at position-2 represented a novel pathway for modifying resveratrol structure in the protection of DNA against peroxyl radical-mediated oxidation.

Structural basis, chemical driving forces and biological implications of flavones as Cu(II) ionophores

A main biochemical property of cancer cells, compared with normal cells, is altered redox status including increased levels of copper to maintain their malignant phenotypes. Thus, increasing copper accumulation, by using ionophores, to disrupt abnormal redox homeostasis of cancer cells may be an important anticancer strategy. Naturally occurring molecules with extraordinarily diverse chemical scaffolds are an important source of inspiration for developing copper ionophores. Dietary flavonoids are well-characterized copper chelators and show cancer chemopreventive potential, but their ionophoric role for redox-active copper and the related biological implications have remained unknown. This study reports, for the first time, the structural basis, chemical driving forces and biological implications of flavones (a widely distributed subgroup of flavonoids) as Cu(II) ionophores, and also provides new insights into cancer chemopreventive mechanism of flavones bearing 3(or 5)-hydroxy-4-keto group. 3-Hydroxyflavone surfaced as a potent Cu(II) ionophore to induce the mitochondria-dependent apoptosis of cancer cells in a redox intervention fashion via sequential proton-loss Cu(II) chelation, GSH-driving releasing of copper and protonation-dependent efflux of the neutral ligand.

Designing piperlongumine-directed anticancer agents by an electrophilicity-based prooxidant strategy: A mechanistic investigation

Piperlongumine (PL), a natural electrophilic alkaloid bearing two α, β-unsaturated imides, is a promising anticancer molecule by targeting the stress response to reactive oxygen species (ROS). Considering that ROS generation depends on electrophilicity of PL, PL-CL was designed as its analog by introducing the α-substituent chlorine on the lactam ring to increase moderately its electrophilicity. In comparison with the parent molecule, this molecule was identified as a stronger ROS (O2(∙-) and H2O2) inducer and cytotoxic agent, and manifested more than 15-fold selectivity toward A549 cells over normal WI-38 cells. Mechanistic study uncovers for the first time that the selenoprotein thioredoxin reductase (TrxR) is one of the targets by which PL-CL promotes the ROS generation. Stronger intracellular TrxR inhibition and higher accumulation of ROS (O2(∙-) and H2O2) are responsible for more effective S-phase arrest and mitochondria-mediated apoptotic induction of A549 cells by PL-CL than PLvia p53-p21-cyclinA/CDK2 and ASK1-JNK/p38 signaling cascade pathways, respectively. This work provides an example of successfully designing PL-directed anticancer agent by an electrophilicity-based prooxidant (ROS-generating agent) strategy and gives added confidence for extending this strategy to other natural products.

Chain elongation analog of resveratrol as potent cancer chemoprevention agent

Resveratrol is identified as a natural cancer chemoprevention agent. There has been a lot of interest in designing and developing resveratrol analogs with cancer chemoprevention activity superior to that of parent molecule and exploring their action mechanism in the past several decades. In this study, we have synthesized resveratrol analogs of compounds A-C via conjugated chain elongation based on isoprene unit retention strategy. Remarkably, cytotoxic activity analysis results indicated that compound B possesses the best proliferation inhibition activity for NCI-H460 cells in all the test compounds. Intriguingly, compound B displayed a higher cytotoxicity against human non-small cell lung cancer cells (NCI-H460) compared to normal human embryonic lung fibroblasts (MRC-5). Afterward, flow cytometry analysis showed that compound B would induce cell apoptosis. We further researched the action mechanism. When NCI-H460 cells were incubated by compound B for 6 or 9 h, respectively, the intracellular reactive oxygen species (ROS) level was enhanced obviously. With elevation of intracellular ROS level, flow cytometry measurement verified mitochondrial transmembrane potential collapse, which was accompanied by the up-regulation of Bax and down-regulation of Bcl-2. More interestingly, compound B increased the expression of caspase-9 and caspase-3, which induced cell apoptosis. Moreover, compound B arrested cell cycle in G0/G1 phase. These are all to provide useful information for designing resveratrol-based chemoprevention agent and understanding the action mechanism.

Resveratrol analogue 4,4'-dihydroxy-trans-stilbene potently inhibits cancer invasion and metastasis

We investigated the preventive effects of resveratrol analogue 4,4′-dihydroxy-trans-stilbene (DHS) on cancer invasion and metastasis. Two different in vivo approaches of mouse and zebrafish lung cancer invasion models were employed in our study. The in vitro results showed that DHS displays potent inhibition on anchorage-dependent or -independent cell growth of LLC cells, leading to impairment of the cell cycle progression with reduction of cell numbers arresting at the G1 phase, an evident accumulation of pre-G1 events correlated with apoptotic behaviour. In addition, DHS induces a marked inhibition of LLC cell migration and matrigel invasion. In a murine lung cancer model, tumour volume, cell proliferation, and tumour angiogenesis were significantly inhibited by DHS. Importantly, liver metastatic lesions were significantly reduced in DHS-treated mice. Similarly, DHS significantly inhibits lung cancer cell dissemination, invasion and metastasis in a zebrafish tumour model. These findings demonstrate that DHS could potentially be developed as a novel therapeutic agent for treatment of cancer and metastasis.

Toward an understanding of the role of a catechol moiety in cancer chemoprevention: The case of copper- and o-quinone-dependent Nrf2 activation by a catechol-type resveratrol analog

SCOPE

Catechol moieties are commonly present in dietary natural products that exert cancer chemopreventive activity. While the oxidative conversion of catechols into their corresponding o-quinones is generally considered to contribute to their cancer chemopreventive effects, the mechanism of the intracellular conversion has not been fully elucidated.

METHODS AND RESULTS

Among resveratrol and its hydroxylated analogs examined, only 3,4-dihydroxy-trans-stilbene exerted cytoprotective effects against t-butylhydroperoxide-induced death of HepG2 cells. This resveratrol analog activated the nuclear factor erythroid-2-related factor 2 (Nrf2) pathway through stimulating phosphorylation of Akt and inducing keap1 modification, thereby resulting in its nuclear translocation and subsequent transcriptional induction of phase II detoxifying enzymes. Its cytoprotective effect through Nrf2 activation was largely abrogated by pretreatment of cells with DTT, a sulfhydryl-containing nucleophile, and neocuproine, a specific chelating agent for copper ions.

CONCLUSION

We identified 3,4-dihydroxy-trans-stilbene as a novel Nrf2 activator that is converted intracellularly into its corresponding o-quinone electrophile by copper ions. The copper-mediated oxidation was required for the Nrf2 activation, subsequent transcriptional induction of phase II detoxifying enzymes and ultimately for cytoprotection. The findings demonstrate a previously underrecognized role for intracellular copper ions in the cancer chemopreventive effects of catechol-containing dietary natural products.

Hexamethoxylated Monocarbonyl Analogues of Curcumin Cause G2/M Cell Cycle Arrest in NCI-H460 Cells via Michael Acceptor-Dependent Redox Intervention

Curcumin, derived from the dietary spice turmeric, holds promise for cancer prevention. This prompts much interest in investigating the action mechanisms of curcumin and its analogues. Two symmetrical hexamethoxy-diarylpentadienones (1 and 2) as cucumin analogues were reported to possess significantly enhanced cytotoxicity compared with the parent molecule. However, the detailed mechanisms remain unclear. In this study, compounds 1 and 2 were identified as the G2/M cell cycle arrest agents to mediate the cytotoxicity toward NCI-H460 cells via Michael acceptor-dependent redox intervention. Compared with curcumin, they could more easily induce a burst of reactive oxygen species (ROS) and collapse of the redox buffering system. One possible reason is that they could more effectively target intracellular TrxR to convert this antioxidant enzyme into a ROS promoter. Additionally, they caused up-regulation of p53 and p21 and down-regulation of redox-sensitive Cdc25C along with cyclin B1/Cdk1 in a Michael acceptor- and ROS-dependent fashion. Interestingly, in comparison with compound 2, compound 1 displayed a relatively weak ability to generate ROS but increased cell cycle arrest activity and cytotoxicity probably due to its Michael acceptor-dependent microtubule-destabilizing effect and greater GST-inhibitory activity, as well as its enhanced cellular uptake. This work provides useful information for understanding Michael acceptor-dependent and redox-mediated cytotoxic mechanisms of curcumin and its active analogues.

Plant derived and dietary phenolic antioxidants: anticancer properties

In this paper, a review of the literature on the phenolic compounds with anticancer activity published between 2008 and 2012 is presented. In this overview only phenolic antioxidant compounds that display significant anticancer activity have been described. In the first part of this review, the oxidative and nitrosative stress relation with cancer are described. In the second part, the plant-derived food extracts, containing identified phenolic antioxidants, the phenolic antioxidants isolated from plants and plant-derived food or commercially available and the synthetic ones, along with the type of cancer and cells where they exert anticancer activity, are described and summarized in tables. The principal mechanisms for their anti-proliferative effects were also described. Finally, a critical analysis of the studies and directions for future research are included in the conclusion.

Theoretical study of complexation of resveratrol with cyclodextrins and cucurbiturils: structure and antioxidative activity

The inclusion complexation of resveratrol with cyclodextrins and cucurbiturils and the influence of complexation on the antioxidative activity of resveratrol have been theoretically studied.

Influence of side chain structure changes on antioxidant potency of the [6]-gingerol related compounds

[6]-Gingerol and [6]-shogaol are the major pungent components in ginger with a variety of biological activities including antioxidant activity. To explore their structure determinants for antioxidant activity, we synthesized eight compounds differentiated by their side chains which are characteristic of the C1-C2 double bond, the C4-C5 double bond or the 5-OH, and the six- or twelve-carbon unbranched alkyl chain. Our results show that their antioxidant activity depends significantly on the side chain structure, the reaction mediums and substrates. Noticeably, existence of the 5-OH decreases their formal hydrogen-transfer and electron-donating abilities, but increases their DNA damage- and lipid peroxidation-protecting abilities. Additionally, despite significantly reducing their DNA strand breakage-inhibiting activity, extension of the chain length from six to twelve carbons enhances their anti-haemolysis activity.

An effective strategy to develop active cinnamic acid-directed antioxidants based on elongating the conjugated chains

To optimize antioxidant activity and lipophilicity of cinnamic acid derivatives (CAs) including ferulic acid, sinapic acid, 3,4-dimethoxycinnamic acid, and p-hydroxycinnamic acid, four analogs bearing an additional double bond between their aromatic ring and propenoic acid moiety were designed and synthesized based on the conjugated chain elongation strategy. The antioxidant performance of the CAs were investigated by 2,2'-diphenyl-1-picrylhydrazyl (DPPH)-scavenging, ferric reducing/antioxidant power, cyclic voltammetry, DNA strand breakage-inhibiting and anti-haemolysis activity assays. It was found that CAs with elongation of conjugated chains display increased DPPH-scavenging, DNA strand breakage-inhibiting and anti-haemolysis activities as compared to their parent molecules, due to their improved hydrogen atom-donating ability and lipophilicity. Overall, this work highlights an effective strategy to develop potential CA-directed antioxidants by elongating their conjugated chain.

Influence of glucuronidation and reduction modifications of resveratrol on its biological activities

Resveratrol (3,5,4'-trihydroxystilbene, RES), a star among dietary polyphenols, shows a wide range of biological activities, but it is rapidly and extensively metabolized into its glucuronide and sulfate conjugates as well as to the corresponding reduced products. This begs the question of whether the metabolites of RES contribute to its in vivo biological activity. To explore this possibility, we synthesized its glucuronidation (3-GR and 4'-GR) and reduction (DHR) metabolites, and evaluated the effect of these structure modifications on biological activities, including binding ability with human serum albumin (HSA), antioxidant activity in homogeneous solutions and heterogeneous media, anti-inflammatory activity, and cytotoxicity against various cancer cell lines. We found that 1) 4'-GR, DHR and RES show nearly equal binding to HSA, mainly through hydrogen bonding, whereas 3-GR adopts a quite different orientation mode upon binding, thereby resulting in reduced ability; 2) 3-GR shows comparable (even equal) ability to RES in FRAP- and AAPH-induced DNA strand breakage assays; DHR, 3-GR, and 4'-GR exhibit anti-hemolysis activity comparable to that of RES; additionally, 3-GR and DHR retain some degree activity of the parent molecule in DPPH.-scavenging and cupric ion-initiated oxidation of LDL assays, respectively; 3) compared to RES, 4'-GR displays equipotent ability in the inhibition of COX-2, and DHR presents comparable activity in inhibiting NO production and growth of SMMC-7721 cells. Relative to RES, its glucuronidation and reduction metabolites showed equal, comparable, or some degree of activity in the above assays, depending on the specific compound and test model, which probably supports their roles in contributing to the in vivo biological activities of the parent molecule.

Plant phytochemicals as new potential drugs for immune disorders and cancer therapy: really a promising path?

Plant phytochemicals represent an exciting opportunity to maintain best health conditions through a balanced and properly administered daily nutrition or dietary supplement and have often been considered a good option for obtaining a few promising, expensive new drugs from plants. Several polyphenolic compounds, such as resveratrol, tea catechins and flavonoids, which are commonly found in vegetables, fruits and plant-derived juices or beverages, exert well-evidenced cardioprotective, neuroprotective, chemopreventive and anti-inflammatory properties, but, nevertheless, further clinical and epidemiological research is required. Most of these botanical byproducts are produced as noxious components by plants, in order to prevent pathogen colonization, insect-mediated damage and also to discourage animals from eating them. An evolutionary theory of stress adaptation would explain how these toxic substances from nature act as protective molecules. A future challenge to achieve a rather complete understanding of these chemical phenol derivatives for human health should deal with the complexity of cellular signalling networks, the epigenetic machinery endowment of the cell and the nonlinear relationship between dose and effectiveness.

Hypohalous acid-mediated halogenation of resveratrol and its role in antioxidant and antimicrobial activities

The reactions of resveratrol with proinflammatory oxidants including hypochlorous and hypobromous acids in phosphate-buffered saline/methanol solution were carried out and eight halogenated resveratrol derivatives differing in the number and position of halogen atoms, and the configuration of double bond were obtained. Halogenation of resveratrol took place only at the aromatic A ring, and interestingly, the halogenation increased antioxidant activity of this parent molecule in the 2,2'-azobis(2-amidinopropane) hydrochloride-induced RBC haemolysis model. Additionally, antimicrobial activity of the derivatives against Gram-positive bacteria, Gram-negative bacteria and fungi were tested, and toward Candida albicans, 2-chloro-resveratrol and 2-bromo-resveratrol were more active than the unmodified form and the reference compound fluconazole.

Synthesis and biological evaluation of hydroxylated 3-phenylcoumarins as antioxidants and antiproliferative agents

Based on the observed biological activities of coumarins and resveratrol, we synthesized fourteen hydroxylated 3-phenylcoumarins (stilbene-coumarin hybrids) including six novel ortho-hydroxy-methoxy substituted derivatives, 1-14, by Perkin reaction. We characterized these compounds concerning their antioxidant activity against 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)-induced pBR322 DNA strand breakage, and their antiproliferative effects on human promyelocytic leukemia HL-60 and human lung adenocarcinoma epithelial A549 cells. Structure-activity relationship information suggests that the introduction of ortho-hydroxy-methoxy groups and ortho-dihydroxy groups on the aromatic A ring could efficiently improve antiproliferative activity. Interestingly, a new derivative, 6-methoxy-7-hydroxy-3-(4'-hydroxyphenyl)coumarin, 9, behaved as a poor antioxidant but appeared to be the most potent antiproliferative agent among the compounds examined, and this activity was mediated by deregulation in cell cycle and induction of apoptosis.