Antioxidant properties of phenyl styryl ketones

Discovery of novel (1S)-(-)-verbenone derivatives with anti-oxidant and anti-ischemic effects

A series of novel (1S)-(-)-verbenone derivatives was synthesized bearing a 4-styryl scaffold. The synthesized compounds were tested for their anti-oxidant, anti-excitotoxic, and anti-ischemic activities. These derivatives significantly reduced oxygen-glucose deprivation-induced neuronal injury and N-methyl-D-aspartic acid-evoked excitotoxicity in cortical neurons. Furthermore, compound 3f was identified as a potent anti-ischemic agent in an in vitro ischemic model, potentially due to the inhibition of N-methyl-D-aspartic acid-evoked excitotoxicity and oxidative/nitrosative stress.

Superoxide scavenging effects of some novel bis-ligands and their solvated metal complexes prepared by the reaction of ligands with aluminum, copper and lanthanum ions

Novel antioxidants have been synthesized and characterized by their chemical properties as antioxidants with high superoxide scavenging activity. (2R,3R)-diphenylethylenediamine is a spacer in antioxidants, and we synthesized targets 11a and 11b by conjugation with o-hydroquinone and p-hydroquinone at the two N-termini, respectively. Superoxide scavenging activities of the plant flavonoid-like 11a and 11b were compared with those of known antioxidants, and shown to increase in the following order: curcumin << ascorbic acid < Trolox < (+)-epicatechin < 11a < quercetin ≤ 11b. Compound 11a also formed a solvated 11a-metal complex with metal ions. The 11a-Cu²⁺ complex was shown to have higher superoxide scavenging activity than that of 11a, 11b, Cu²⁺, and the 11a-Al³⁺ and 11a-La³⁺ complexes, whereas the 11a-Al3+ complex increased rather than decreased superoxide levels. The 11a-Al³⁺ complex did not abstract one electron from the SOMO of O₂⁻· since the HOMO and LUMO phases of Al³⁺ do not exist in the center of the 11a-Al³⁺ complex. However, the SOMO of the 11a-Cu²⁺ complex distributed in the center of Cu²⁺ may abstract one electron from the SOMO of O₂⁻·. These results suggest that 11a and 11b are powerful antioxidants.

Curcumin blocks activation of pancreatic stellate cells

Activated pancreatic stellate cells (PSCs) play a pivotal role in the pathogenesis of pancreatic fibrosis and inflammation. Inhibition of activation and cell functions of PSCs is a potential target for the treatment of pancreatic fibrosis and inflammation. The polyphenol compound curcumin is the yellow pigment in curry, and has anti-inflammatory and anti-fibrotic properties. We here evaluated the effects of curcumin on the activation and cell functions of PSCs. PSCs were isolated from rat pancreas tissue and used in their culture-activated, myofibroblast-like phenotype unless otherwise stated. The effects of curcumin on proliferation, alpha-smooth muscle actin gene expression, monocyte chemoattractant protein (MCP)-1 production, and collagen expression were examined. The effect of curcumin on the activation of freshly isolated cells in culture was also assessed. Curcumin inhibited platelet-derived growth factor (PDGF)-induced proliferation, alpha-smooth muscle actin gene expression, interleukin-1beta- and tumor necrosis factor (TNF)-alpha-induced MCP-1 production, type I collagen production, and expression of type I and type III collagen genes. Curcumin inhibited PDGF-BB-induced cyclin D1 expression and activation of extracellular signal-regulated kinase (ERK). Curcumin inhibited interleukin-1beta- and TNF-alpha-induced activation of activator protein-1 (AP-1) and mitogen-activated protein (MAP) kinases (ERK, c-Jun N-terminal kinase (JNK), and p38 MAP kinase), but not of nuclear factor-kappaB (NF-kappaB). In addition, curcumin inhibited transformation of freshly isolated cells to myofibroblast-like phenotype. In conclusion, curcumin inhibited key cell functions and activation of PSCs.

Antioxidant evaluations of novel N-H and N-substituted indole esters

The anti-lipid peroxidation (LP) activity and anti-superoxide formation (SOD) of new N-H and N-substituted indole derivatives were evaluated to determine their antioxidant activity. The results showed that compounds 1, 2, 5, 9 and 12 demonstrate considerable inhibition of lipid peroxidation of mouse liver homogenate. On the other hand, compounds 5 and 12 showed anti-superoxide formation activity at a concentration of 10(-4) M. Consequently, it can be concluded that these compounds exhibit important activity compared with reference compound alpha-tocopherol (vitamin E).

Antioxidant and cytoprotective activity of indole derivatives related to melatonin

Melatonin (MLT) is known for its radical scavenger activity, which had been related to its ability to protect neuronal cells from different kinds of oxidative stress. In particular, MLT protects rat cerebellum granular cells from kainate-induced necrosis at concentrations higher than 100 microM, and is able to reduce lipoperoxidation induced by radical stress in rat brain homogenate at similar concentrations. On the other hand, MLT has nanomolar affinity for its membrane receptors (MT1 and MT2), and these are completely saturated at the high concentrations employed when the cytoprotective effect is observed. Other indole derivatives are also known to possess antioxidant and cytoprotective activity. In order to dissociate the cytoprotective effect of MLT from its receptor affinity, and to investigate the structure-activity relationships (SAR) between this effect and some potentially relevant chemical properties, we prepared a series of indole derivatives, where the structure of MLT was gradually modulated, varying the 5-methoxy group nature and position, the acylaminoethyl chain position, and by the introduction of lipophilic groups. These modifications resulted in a set of compounds having different receptor affinity and intrinsic activity, different lipophilicity, and different substitution at the indole nucleus. The compounds were tested for their antioxidant potency by the ABTS test and by inhibition of rat brain homogenate lipoperoxidation; their cytoprotective effect was also estimated from the inhibition of kainate-induced cellular death on rat cerebellum granular cells, and the results were evaluated by SAR comparison and QSAR analysis. An isomer of MLT resulted more potent and effective than MLT itself in the cytoprotection test, although it showed similar potency in the peroxidation test, and it was devoid of the ability to stimulate MT1 and MT2 receptors. This compound was selected as the lead compound for a further SAR study, devoted to the optimization of the cytoprotective effect and to the investigation on its mechanism.

Structure-activity relationships for the inhibition of lipid peroxidation and the scavenging of free radicals by synthetic symmetrical curcumin analogues

A number of ring substituted analogues of curcumin were synthesized. Their antioxidant properties were studied using three models, inhibition of lipid peroxidation, scavenging of 1,1'-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azinobis(3-ethyl-benzthiazoline-6-sulphonate radical (ABTS+.). In all the models, the phenolic analogues were more active than the non-phenolic analogues, some of which were inactive. The highest antioxidant activity was obtained when the phenolic group was sterically hindered by the introduction of two methyl groups at the ortho position. This and several other compounds were more active than the standard antioxidants alpha-tocopherol and trolox. This study has demonstrated that the phenolic group is important for the antioxidant activity of curcumin and that the structural features that enhance the antioxidant properties of phenols are optimized in curcumin to a significant extent.

Free radical scavenging ability and antioxidant efficiency of curcumin and its substituted analogue

Free radical reactions of curcumin and its ethoxy substituted derivative (C1) 1,7-bis-(4-hydroxy-3-ethoxy phenyl)-1,6-heptadiene-3,5-dione have been studied using a pulse radiolysis technique in homogeneous aqueous-organic solutions like acetonitrile-water and isopropanol-water mixtures, as well as in neutral TX-100 and cationic CTAB micellar solutions. The phenoxyl radicals of curcumin or C1 were generated by one-electron transfer to several oxidants like N(3)(.), Br(2)(-.), CCl(3)O(2)(.), glutathione radicals which exhibit absorption from a 300-600-nm wavelength region with the maximum at 490-500 nm. Other important properties of the phenoxyl radicals such as extinction coefficient, radical lifetime and their formation and decay rate constants were also determined in these systems. The antioxidant property of curcumin and C1 were estimated in terms of their ability to inhibit the lipid peroxidation in liposomes and also in terms of trolox equivalent antioxidant capacity (TEAC). The results were compared with alpha-tocopherol.

Inhibitory effects of dehydrozingerone and related compounds on 12-O-tetradecanoylphorbol-13-acetate induced Epstein-Barr virus early antigen activation

Dehydrozingerone, 4-(4-hydroxy-3-methoxyphenyl)-3-buten-2-one, is half an analog of curcumin which is known to have anti-tumor activity. The anti-tumor promoting activity of dehydrozingerone was evaluated by determining the inhibitory effect on Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA). The concentration needed for 50% inhibition of the tumor promotion (IC50) of dehydrozingerone was similar to that of curcumin. To elucidate the structure-activity relationship on the anti-tumor promoting activity, dehydrozingerone, curcumin, isoeugenol, which has no carbonyl group in the side chain, benzalacetone, which is the basic structure of dehydrozingerone, o-dehydrozingerone, which is the ortho-hydroxyl substituted compound of dehydrozingerone, and their related compounds were investigated using the in vitro short-term assay on TPA-induced EBV-EA activation. o-Dehydrozingerone showed the most potent inhibitory effect in a series of tested dehydrozingerone derivatives and their related monosubstituted benzalacetones. This suggests that the occupation at both ortho positions of the hydroxyl group enhances the anti-tumor promoting activity. Isoeugenol inhibited the tumor promoting activity at a concentration of about one-third of the IC50 of dehydrozingerone. This indicates that the carbonyl group in the side chain has a negative impact on the anti-tumor promoting activity. The inhibitory effects of the carbon-carbon bond in the side chain were studied using benzylacetone with a single bond, benzalacetone with a double bond and 4-phenyl-3-butyn-2-one with a triple bond. 4-Phenyl-3-butyn-2-one inhibited the most potent activity followed by benzalacetone and benzylacetone.

Gastroprotective effect of 1-phenyl-3-(4-hydroxy-3,5-di-tert-butylphenyl)prop-2-en-1-one in rats

1-Phenyl-3-(4-hydroxy-3,5-di-tert-butylphenyl)prop-2-en-1-one (PHP), an antioxidant, has been studied for gastroprotective activity in-vitro and in-vivo, more specifically for its capacity to inhibit in-vitro iron- and copper-driven oxidant damage at acidic pH values mimicking intragastric conditions in the clinical setting. Our studies showed significant inhibition of both iron- and copper-driven oxidant damage at pH 3.5 and 5.3. Intragastric and intraperitoneal administration of PHP (250 mg kg(-1)) reduced gastric mucosal haemorrhagic lesions in stress-induced and ethanol-induced rat models. The gastroprotective effect of PHP against ethanol was reversed significantly by prior treatment with a dose of indomethacin that inhibits prostaglandin biosynthesis, indicating a possible role of prostaglandins in its gastroprotective effect. Treatment of PHP replenished reduced levels of gastric mucosal non-protein sulphydryls in ethanol-treated rats, suggesting the mediation of its effect through sulphydryls. These results indicate that PHP was active at acidic pH. This is an interesting observation because highly acidic pH is known to be important in the development of gastric ulcers. Our study suggests that PHP might protect gastric mucosa by its capacity to scavenge free radicals.

Effect of bile acids on lipid peroxidation: the role of iron

The toxic effect of hydrophobic bile acids is claimed to be in part mediated by lipid peroxidation. Conversely, antioxidant properties of tauroursodeoxycholic acid (TUDC), a hydrophilic bile acid, have been suggested as a possible mechanism by which TUDC confers its beneficial effect in a variety of diseases. We have investigated the effect of taurodeoxycholic acid (TDC), a hydrophobic bile acid and TUDC on lipid peroxidation using a pure lipid system both in the presence and absence of iron ions. Neither TDC nor TUDC showed any effect on spontaneous lipid peroxidation of phosphatidylcholine liposomes or sodium arachidonate solution. This lack of effect excludes the possibility of direct prooxidant or antioxidant properties for TDC and TUDC. Addition of ferrous ions (0.1 mM) to the lipid system brought about a linear increase in lipid peroxidation with time. The presence of TDC caused an increase in the rate and extent of iron-stimulated lipid peroxidation. The propensity of bile acids to increase iron-induced lipid peroxidation was related to hydrophobicity of the individual bile acids, with the highest effect observed with taurolithocholic acid, whereas TUDC did not have any influence. The TDC-induced increase in the iron-stimulated lipid peroxidation was concentration dependent. Addition of TUDC (10 mM) completely abolished the effect of TDC (2 mM) on iron-induced lipid peroxidation. This finding suggests that TUDC does not function as an antioxidant per se but may prevent lipid peroxidation caused by TDC. In conclusion, only in the presence of iron ions, hydrophobic bile acids may enhance lipid peroxidation. TUDC has no antioxidant activity per se but may counter the TDC-induced increase in iron-stimulated lipid peroxidation.

New curcuminoids isolated from Zingiber cassumunar protect cells suffering from oxidative stress: a flow-cytometric study using rat thymocytes and H2O2

Effects of new complex curcuminoids (cassumunin A and cassumunin B) isolated from tropical ginger, Zingiber cassumunar, were examined in dissociated rat thymocytes suffering from oxidative stress induced by 3 mM hydrogen peroxide by using a flow cytometer and ethidium bromide. The effects were compared with those of curcumin, a natural antioxidant, whose chemical structure is included in those of cassumunins A and B. Pretreatment of rat thymocytes with the respective cassumunins at concentrations ranging from 100 nM to 3 microM dose-dependently prevented the hydrogen peroxide (H2O2)-induced decrease in cell viability. It had the same action, although less effective, against the treatment with cassumunin A or B (3 microM) immediately after or 60 min after start of the oxidative stress. Respective potencies of cassumunins A and B in protecting the cells suffering from H2O2-induced oxidative stress were greater than that of curcumin. It is suggested that cassumunins A and B may possess a potent protective action on living cells suffering from oxidative stress.