Studies on antioxidants: their carcinogenic and modifying effects on chemical carcinogenesis

Antioxidant and hepatoprotective potential of essential oils of coriander (Coriandrum sativum L.) and caraway (Carum carvi L.) (Apiaceae)

Essential oils of Coriandrum sativum L. and Carum carvi L. fruits were analyzed by gas chromatography-mass spectrometry and assayed for their in vitro and in vivo antioxidant activity and hepatoprotective effect against carbon tetrachloride (CCl(4)) damage. The in vitro antioxidant activity was evaluated as a free radical scavenging capacity (RSC), measured as scavenging activity of the essential oils on 2,2-diphenyl-1-picrylhydrazyl (DPPH(*)) and OH radicals and effects on lipid peroxidation (LP) in two systems of induction. Some liver biochemical parameters were determined in animals pretreated with essential oils and later intoxicated with CCl(4) to assess in vivo hepatoprotective effect. Tested essential oils were able to reduce the stable DPPH(*) in a dose-dependent manner and to neutralize H(2)O(2), reaching 50% neutralization with IC(50) values of <2.5 microL/mL for Carvi aetheroleum and 4.05 microL/mL for Coriandri aetheroleum . Caraway essential oil strongly inhibited LP in both systems of induction, whereas coriander essential oil exhibited prooxidant activity. In vivo investigation conferred leak of antioxidative capacity of coriander essential oil, whereas the essential oil of caraway appeared promising for safe use in folk medicine and the pharmaceutical and food industries.

Total phenolic contents and antioxidant capacities of selected chinese medicinal plants

Antioxidant capacities of 56 selected Chinese medicinal plants were evaluated using the Trolox equivalent antioxidant capacity (TEAC) and ferric reducing antioxidant power (FRAP) assays, and their total phenolic content was measured by the Folin-Ciocalteu method. The strong correlation between TEAC value and FRAP value suggested that the antioxidants in these plants possess free radical scavenging activity and oxidant reducing power, and the high positive correlation between antioxidant capacities and total phenolic content implied that phenolic compounds are a major contributor to the antioxidant activity of these plants. The results showed that Dioscorea bulbifera, Eriobotrya japonica, Tussilago farfara and Ephedra sinica could be potential rich sources of natural antioxidants.

Differentiation between phenol- and amino-substances in voltammetry determination of synthetic antioxidants in oils

The paper describes a method of voltammetric determination of antioxidants in lubricating oils developed with the use of Linear Sweep Voltammetry (LSV) and Fast Scan Differential Pulse Voltammetry (FSDPV). Experimental conditions have been found for simultaneous determination of phenol-based antioxidants and amino-antioxidants: the phenols can be electrochemically oxidized using the polarisation of gold disc electrode (AuDE) in the potential range of 0–1400 mV in 0.2 M H2SO4 in the presence of ethanol and acetonitrile at the ratio of 3:1. Secondary aromatic amines can be determined directly in this supporting electrolyte; the presence of phenolic antioxidants does not interfere with this analysis. On the other hand, secondary aromatic amines interfere with the determination of phenolic substances; therefore, the amines present have to be eliminated in a suitable way. A procedure for masking the aromatic amines using their reaction with nitrous acid has been suggested and optimised. The nitrosamines thus formed can be used for sensitive and selective determination of amino-antioxidants by means of cathodic reduction on the hanging mercury drop electrode (HMDE) using Fast Scan Differential Pulse Voltammetry. The method was applied in analysis of real samples of lubricating oils.

Evaluation of functional stability and batch-to-batch reproducibility of a Castanea sativa leaf extract with antioxidant activity

A growing body of evidence suggests that free radicals are generated by UV irradiation being responsible for skin injury. In this regard, the topical use of formulations composed of plant extracts with antioxidant activity could represent a useful strategy for the prevention of photoaging and oxidative-stress-mediated diseases. The aim of this study was to assess the reproducibility of the extraction method and the functional stability of a Castanea sativa leaf extract in view of its application as topical antioxidant. Measurements of 1,1-diphenyl-2-picryl hydrazyl (DPPH) scavenging activity, total phenols (measured by the Folin Ciocalteu assay) and phenolic composition (high-performance liquid chromatography unit coupled to a UV detector) were carried out on three different batches. The influence of pH and temperature on the extract's DPPH scavenging activity was assessed in aqueous and glyceric solutions (0.025% w/v) over a 3-month period. Minor differences were found between the three extract batches for all the evaluated parameters, and therefore the reproducibility of the extraction method can be inferred. pH presented a great influence in the extract functional stability. Major antioxidant activity decrease was found at pH 7.1, while lower changes were observed at pH 5. Glyceric solutions were stable throughout the test period. At 40 degrees C and pH 5, a marked decrease of activity was observed. Again, glyceric solutions were the most stable, even at 40 degrees C. Proper selection of pH and solvent is mandatory to ensure the stability of the studied extract after being incorporated in semisolid forms. In view of these results, glycerine is proposed as the best vehicle for topical formulations incorporating C. sativa leaf extract, which should have a pH around 5.

Factors to consider in the use of stem cells for pharmaceutic drug development and for chemical safety assessment

Given the reality of the inadequacies of current concepts of the mechanisms of chemical toxicities, of the various assays to predict toxicities from current molecular, biochemical, in vitro and animal bioassays, and of the failure to generate efficacious and safe chemicals for medicines, food supplements, industrial, consumer and agricultural chemicals, the recent NAS Report, "Toxicity Testing in the 21st Century: A Vision and a Strategy", has drawn attention to a renewed examination of what needs to be done to improve our current approach for better assessment of potential risk to human health. This "Commentary" provides a major paradigm challenge to the current concepts of how chemicals induce toxicities and how these various mechanisms of toxicities can contribute to the pathogenesis of some human diseases, such as birth defects and cancer. In concordance with the NAS Report to take "... advantage of the on-going revolution in biology and biotechnology", this "Commentary" supports the use of human embryonic and adult stem cells, grown in vitro under simulated "in vivo niche conditions". The human being should be viewed "as greater than the sum of its parts". Homeostatic control of the "emergent properties" of the human hierarchy, needed to maintain human health, requires complex integration of endogenous and exogenous signaling molecules that control cell proliferation, differentiation, apoptosis and senescence of stem, progenitor and differentiated cells. Currently, in vitro toxicity assays (mutagenesis, cytotoxicity, epigenetic modulation), done on 2-dimensional primary rodent or human cells (which are always mixtures of cells), on immortalized or tumorigenic rodent or human cell lines do not represent normal human cells in vivo [which do not grow on plastic and which are in micro-environments representing 3 dimensions and constantly interacting factors]. In addition, with the known genetic, gender, and developmental state of cells in vivo, any in vitro toxicity assay will need to mimic these conditions in vitro. More specifically, while tissues contain a few stem cells, many progenitor/transit cells and terminally differentiated cells, it should be obvious that both embryonic and adult stem cells would be critical "target" cells for toxicity testing. The ultimate potential for in vitro testing of human stem cells will to try to mimic a 3-D in vitro micro-environment on multiple "organ-specific and multiple genotypic/gender "adult stem cells. The role of stem cells in many chronic diseases, such as cancer, birth defects, and possibly adult diseases after pre-natal and early post-natal exposures (Barker hypothesis), demands toxicity studies of stem cells. While alteration of gene expression ("toxico-epigenomics") is a legitimate endpoint of these toxicity studies, alteration of the quantity of stem cells during development must be serious considered. If the future utility of human stem cells proves to be valid, the elimination of less relevant, expensive and time-consuming rodent and 2-D human in vitro assays will be eliminated.

Differential regulation of the hydrogen-peroxide-induced inhibition of gap-junction intercellular communication by resveratrol and butylated hydroxyanisole

The present study was performed to evaluate the effects of two different phenolic antioxidants, resveratrol (3,5,4'-trihydroxystilbene) and butylated hydroxyanisole (BHA), on the hydrogen peroxide (H2O2)-induced inhibition of gap-junction intercellular communication (GJIC) in WB-F344 rat liver epithelial cells (WB-F344). Resveratrol is a naturally occurring polyphenolic antioxidant; on the other hand, BHA is a synthetic phenolic compound. We found that only resveratrol protects WB-F344 cells from H2O2-induced inhibition of GJIC, and BHA has no effect. The extracellular-signal-regulated protein kinase 1/2 (ERK1/2)-connexin 43 (Cx43) signaling pathway is crucial for the regulation of GJIC in rat liver epithelial cells, and resveratrol, but not BHA, blocked the H2O2-induced phosphorylation of Cx43, a critical regulator of GJIC, and ERK1/2 in WB-F344 cells. Resveratrol appears to attenuate the H2O2-mediated ERK1/2-Cx43 signaling pathway and consequently reverses H2O2-mediated inhibition of GJIC. DPPH and ABTS radical-scavenging assays revealed that the protective effect of resveratrol on the H2O2-mediated inhibition of GJIC was not mediated through its free radical-scavenging activity.

Purification, structural characterization, and antioxidant activity of antioxidant substance from the red seaweed Gloiopeltis tenax

An antioxidant substance (AOS) obtained from an enzymatic extract of the red seaweed Gloiopeltis tenax was purified by DEAE-Sephadex CL-6B and Sephadex G-100 column chromatography. The purification yield of AOS was 14.3%. The AOS predominantly contained fucose, mannose, and galactose but also contained a sulfate group. The structure of AOS was investigated by periodate oxidation, desulfation, Fourier transform-infrared spectroscopy, and nuclear magnetic resonance spectroscopy. AOS was mainly composed of alternating units of beta-D-Glc(1 --> 2)alpha-D-Man(1 --> 4)beta-D-Gal(1 --> 4)alpha-D-Man(1 --> 4)beta-D-Gal alpha-D-Man (1 --> 4) beta-D-Glc (or Xyl)- and branched linkage of alpha-D-Man(1 --> 3) alpha-D-Fuc. In addition, the fucose residues were shown to be 2-O- and 4-O-sulfated and, therefore, were either terminal or 3-linked. The antioxidative activity of AOS was measured using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay and the beta-carotene-linoleate assay systems and was compared with those of butylated hydroxytoluene and ascorbic acid (AscA). The results showed that AOS exhibited higher antioxidative activity than AscA in the DPPH assay model and in the beta-carotene-linoleate assay system at all of the four concentration levels tested (from 50 to 200 microg/mL). These results suggested that AOS from the red seaweed G. tenax is an efficient novel antioxidant.

Antioxidant activities of extracts and main components of Pigeonpea [Cajanus cajan (L.) Millsp.] leaves

Antioxidant activities of the aqueous and ethanol extracts of pigeonpea [Cajanuscajan (L.) Millsp.] leaves, as well as petroleum ether, ethyl acetate, n-butanol and water fractions and the four main compounds separated from the ethanol extract, i.e. cajaninstilbene acid (3-hydroxy-4-prenylmethoxystilbene-2-carboxylic acid), pinostrobin, vitexin and orientin, were examined by a DPPH radical-scavenging assay and a β-carotene-linoleic acid test. In the DPPH system, the antioxidant activity of the ethanol extracts was superior to that of the aqueous extracts, with IC₅₀ values were 242.01 and 404.91 µg/mL, respectively. Among the four fractions, the ethyl acetate one showed the highest scavenging activity, with an IC₅₀ value of 194.98 µg/mL. Cajaninstilbene acid (302.12 µg/mL) and orientin (316.21 µg/mL) showed more efficient radical-scavenging abilities than pinostrobin and vitexin. In the β-carotene-linoleic acid test, the inhibition ratio (%) of the ethyl acetate fraction (94.13%±3.41%) was found to be the highest, being almost equal to the inhibition capacity of the positive control BHT (93.89%±1.45%) at 4 mg/mL. Pinostrobin (>500 µg/mL) and vitexin (>500 µg/mL) showed insignificant antioxidant activities compared with cajaninstilbene (321.53 µg/mL) and orientin (444.61 µg/mL). In general, the ethyl acetate fraction of the ethanol extract showed greater activity than the main compounds in both systems, such results might be attributed to the synergistic effects of the components. The antioxidant activities of all the tested samples were concentration-dependent. Based on the results obtained, we can conclude that the pigeonpea leaf extracts may be valuable natural antioxidant sources and are potentially applicable in both medicine and the healthy food industry.

PRODUCTION OF NATURAL BUTYLATED HYDROXYTOLUENE AS AN ANTIOXIDANT BY FRESHWATER PHYTOPLANKTON(1)

Butylated hydroxytoluene (BHT) is one of the synthetic antioxidant agents commonly used for food additives. In the present study, we determined that four freshwater phytoplankton, including a green alga (Botryococcus braunii Kütz.) and three cyanobacteria [Cylindrospermopsis raciborskii (Wolłosz.) Seenaya et Sabba Raju, Microcystis aeruginosa (Kütz.) and Oscillatoria sp.] were capable of producing this compound. Hexane extracts from all the studied species exhibited various degrees of antioxidative properties when they were tested with the β-carotene-linoleate (β-CL) assay and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free-radical-scavenging assay. The highest antioxidant activity was observed in the crude extracts of M. aeruginosa and B. braunii, which displayed a similar activity to synthetic BHT. Gas chromatography/mass spectroscopy (GC-MS) analysis of the purified fractions revealed that the active compound was identical to synthetic BHT. Culturing under various irradiances gave rise to different magnitudes of BHT production in cyanobacterial cells, showing that more BHT was produced in the cells irradiated with a higher light intensity, and its production was irradiance dependent. Moreover, the quantity of cellular BHT displayed a positive correlation with the antioxidative activity of the tested species. The present study confirms the production of BHT in all four of the studied freshwater phytoplankton and suggests that these species constitute a potential source for producing natural BHT.

Oak leaf extract as topical antioxidant: free radical scavenging and iron chelating activities and in vivo skin irritation potential

The topical application of antioxidants may be beneficial for the protection of the skin against UV damage. An extract of Quercus robur leaves was prepared and evaluated considering its putative application as topical antioxidant. The solvent and extractive method selection was monitored by 1,1-diphenyl-2-picryl hydrazyl (DPPH) free radical scavenging activity and polyphenols extraction (measured by the Folin Ciocalteu assay). Iron chelating activity and the phenolic composition (HPLC/DAD) were assessed on the extract obtained under optimized conditions. Skin irritation potential was investigated by performing an in vivo patch test in 19 volunteers. The extraction solvent which resulted in the highest activity was ethanol:water (4:6) and thus it was selected for further preparation of this extract. The IC50s for the iron chelation and DPPH scavenging assays were 153.8 +/- 26.3 microg x mL-1 and 7.53 +/- 0.71 microg x mL-1 (mean +/- SD), respectively. The total phenolic content was found to be 346.3 +/- 6.7 mg gallic acid equivalents (GAE)/g extract (mean +/- SD). Three phenolic compounds were identified in the extract namely: ellagic acid, rutin and hyperoside. The major identified component was ellagic acid. The patch test carried out showed that the extract can be regarded as safe for topical application.

Chemical composition and antioxidant property of holy basil (Ocimum sanctum L.) leaves, stems, and inflorescence and their in vitro callus cultures

In this study, the chemical constituents and antioxidant property of holy basil (Ocimum sanctum Linn.) field-grown plant parts (leaves, stems, and inflorescence) were compared with those of respective callus cultures induced from each explant in in vitro. The callus cultures were successfully initiated on Murashige and Skoog (MS) medium supplemented with 2,4-dichlorophenoxy acetic acid (2,4-D) (1 mg/L) combined with different concentrations (0.1-0.5 mg/L) of kinetin as plant growth regulators. The distribution of phenolic compounds in these extracts was analyzed using reverse phase high-performance liquid chromatography with reference standards. Interestingly, rosmarinic acid (RA) was found to be the predominant phenolic acid in all callus extracts in comparison with field-grown plant parts. In this study, the antioxidant activity of the extracts was evaluated with six different in vitro antioxidant-testing systems. Their activities of scavenging superoxide anion radicals, 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH), hydroxyl radicals, hydrogen peroxide, chelating ferrous iron, and ferric ion reducing potential were assessed. The antioxidant activity was increased in all testing systems with increasing amounts of extract. However, at the same concentration, the callus extracts exhibited higher antioxidant activity in all of the testing systems than the extract obtained from field-grown plant parts. The data obtained from this study suggested the possibility of the isolation of a high content of RA from in vitro callus cultures rather than field-grown plant organs of holy basil.

Evaluation of two methods for the extraction of antioxidants from medicinal plants

The efficiencies of two traditional extraction methods used in Chinese medicine (the decoction method and the maceration method) were evaluated for the extraction of antioxidants from medicinal plants. A group of medicinal plants possessing nutritious and tonic functions were chosen as model plants. A commonly used extraction method was used as a reference method. The antioxidant capacities and total phenolic contents of the extracts were measured by ferric-reducing antioxidant power and Trolox equivalent antioxidant capacity assays as well as the Folin-Ciocalteu method, respectively. The results obtained indicated that the two traditional extraction methods could effectively extract antioxidants from medicinal plants. These extraction methods can be applied to the analysis and purification of antioxidants in plants, respectively. At home, people can use these methods to extract antioxidants from plants for consumption. In the food industry, these methods could be utilized to prepare crude extracts from plants containing antioxidants for use as food additives.