Antioxidants2014, 3(4), 671-683; doi:10.3390/antiox3040671 - published 20 October 2014 Show/Hide Abstract
Abstract: The objective of the present work was to investigate the anti-oxidative potential of methanolic extract of Carissa opaca roots and its fractions in solvents of different polarities. Total phenolic (TPC) and flavonoid (TFC) contents of methanolic extract were 211.95 ± 0.78 μg/mL gallic acid equivalents (GAE) and 8.35 ± 0.21 μg/mL rutin equivalents (RE), respectively. Ethyl acetate contained the highest amounts of both (TFC, 11.8 ± 0.28 RE; TPC, 342.80 ± 0.42 GAE) followed by chloroform fraction (TFC, 7.50 ± 0.14 RE; TPC, 275.85 ± 0.50 GAE). Extract and fractions displayed remarkable DPPH radical scavenging activity. EC50 values of methanolic extract was 0.88 mg/mL, while that of hexane, chloroform, ethyl acetate, n-butanolic and aqueous fractions were 0.58, 0.38, 0.29, 0.36 and 5.83 mg/mL, respectively, ethyl acetate fraction being most potent. The ethyl acetate fraction also showed the highest activity in terms of reducing power, phosphomolybdate and ABTS assays. All the fractions showed fairly good lipid peroxidation inhibitory activity, which remained almost constant over three days. Based on the results it can be concluded that roots of Carissa opaca contains phytochemicals with exploitable antioxidant, free radical scavenging, and lipid peroxidation inhibitory potential.
Antioxidants2014, 3(4), 649-670; doi:10.3390/antiox3040649 - published 17 October 2014 Show/Hide Abstract
Abstract: Interaction between host cells and microbes is known as crosstalk. Among other mechanisms, this takes place when certain molecules of the micro-organisms are recognized by the toll-like receptors (TLRs) in the body cells, mainly in the intestinal epithelial cells and in the immune cells. TLRs belong to the pattern-recognition receptors and represent the first line of defense against pathogens, playing a pivotal role in both innate and adaptive immunity. Dysregulation in the activity of such receptors can lead to the development of chronic and severe inflammation as well as immunological disorders. Among components present in the diet, flavonoids have been suggested as antioxidant dietary factors able to modulate TLR-mediated signaling pathways. This review focuses on the molecular targets involved in the modulatory action of flavonoids on TLR-mediated signaling pathways, providing an overview of the mechanisms involved in such action. Particular flavonoids have been able to modify the composition of the microbiota, to modulate TLR gene and protein expression, and to regulate the downstream signaling molecules involved in the TLR pathway. These synergistic mechanisms suggest the role of some flavonoids in the preventive effect on certain chronic diseases.
Antioxidants2014, 3(4), 636-648; doi:10.3390/antiox3040636 - published 13 October 2014 Show/Hide Abstract
Abstract: The number of putative neuroprotective compounds with antioxidant activity described in the literature continues to grow. Although these compounds are validated using a variety of in vivo and in vitro techniques, they are often evaluated initially using in vitro cell culture techniques in order to establish toxicity and effective concentrations. Bothin vivo and in vitro methodologies have their respective advantages and disadvantages, including, but not limited to, cost, time, use of resources and technical limitations. This review expands on the inherent benefits and drawbacks of in vitro and in vivo methods for assessing neuroprotection, especially in light of proper evaluation of compound efficacy and neural bioavailability. For example, in vivo studies can better evaluate the effects of protective compounds and/or its metabolites on various tissues, including the brain, in the whole animal, whereas in vitro studies can better discern the cellular and/or mechanistic effects of compounds. In particular, we aim to address the question of appropriate and accurate extrapolation of findings from in vitro experiment-where compounds are often directly applied to cellular extracts, potentially at higher concentrations than would ever cross the blood-brain barrier—to the more complex scenario of neuroprotection due to pharmacodynamics in vivo.
Antioxidants2014, 3(3), 618-635; doi:10.3390/antiox3030618 - published 19 September 2014 Show/Hide Abstract
Abstract: The aim of this study was to determine the in vitro antioxidant activity, free radical scavenging property and the beneficial effects of extracts of various parts of Syzygium guineense in reducing oxidative stress damage in the liver. The effects of extracts on free radicals were determined on radicals DPPH, ABTS, NO and OH followed by the antioxidant properties using Ferric Reducing Antioxidant Power assay (FRAP) and hosphomolybdenum (PPMB). The phytochemical screening of these extracts was performed by determination of the phenolic content. The oxidative damage inhibition in the liver was determined by measuring malondialdehyde (MDA) as well as the activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and peroxidase. Overall, the bark extract of the ethanol/water or methanol showed the highest radical scavenging activities against DPPH, ABTS and OH radicals compared to the other extracts. This extract also contained the highest phenolic content implying the potential contribution of phenolic compounds towards the antioxidant activities. However, the methanol extract of the root demonstrated the highest protective effects of SOD and CAT against ferric chloride while the hydro-ethanol extract of the leaves exhibited the highest inhibitory effects on lipid peroxidation. These findings suggest that antioxidant properties of S. guineense extracts could be attributed to phenolic compounds revealed by phytochemical studies. Thus, the present results indicate clearly that the extracts of S. guineense possess antioxidant properties and could serve as free radical inhibitors or scavengers, acting possibly as primary antioxidants. The antioxidant properties of the bark extract may thus sustain its various biological activities.
Antioxidants2014, 3(3), 604-617; doi:10.3390/antiox3030604 - published 17 September 2014 Show/Hide Abstract
Abstract: Euphorbia tirucalli (E. tirucalli) is now widely distributed around the world and is well known as a source of traditional medicine in many countries. This study aimed to utilise response surface methodology (RSM) to optimise ultrasonic-assisted extraction (UAE) conditions for total phenolic compounds (TPC) and antioxidant capacity from E.tirucalli leaf. The results showed that ultrasonic temperature, time and power effected TPC and antioxidant capacity; however, the effects varied. Ultrasonic power had the strongest influence on TPC; whereas ultrasonic temperature had the greatest impact on antioxidant capacity. Ultrasonic time had the least impact on both TPC and antioxidant capacity. The optimum UAE conditions were determined to be 50 °C, 90 min. and 200 W. Under these conditions, the E.tirucalli leaf extract yielded 2.93 mg GAE/g FW of TPC and exhibited potent antioxidant capacity. These conditions can be utilised for further isolation and purification of phenolic compounds from E. tirucalli leaf.
Antioxidants2014, 3(3), 592-603; doi:10.3390/antiox3030592 - published 10 September 2014 Show/Hide Abstract
Abstract: A prominent feature of Friedreich’s ataxia (FRDA) is the neurodegeneration of the central and peripheral nervous systems, but little information is available about the mechanisms leading to neuronal damage in this pathology. Currently, no treatments delay, prevent, or reverse the inexorable decline that occurs in this condition. Evidence of oxidative damage has been demonstrated in Friedreich’s ataxia, and this damage has been proposed as the origin of the disease. Nevertheless, the role of oxidative stress in FRDA remains debatable. The lack of direct evidence of reactive oxygen species overproduction in FRDA cells and tissues and the failure of exogenous antioxidants to rescue FRDA phenotypes questions the role of oxidative stress in this pathology. For example, the antioxidant “idebenone” ameliorates cardiomyopathy in FRDA patients, but this therapy does not improve neurodegeneration. To date, no known pharmacological treatment with antioxidant properties cures or delays FRDA neuropathology. This review reports and discusses the evidence of oxidative stress in FRDA and focuses on the existing knowledge of the apparent ineffectiveness of antioxidants for the treatment of neuronal damage.