http://www.mdpi.com/journal/antioxidants Latest open access articles published in Antioxidants at http://www.mdpi.com/journal/antioxidants http://www.mdpi.com/2076-3921/2/2/37 The antioxidant activity and the chemical composition of methanol extracts from peel and pulp belonging to two species of Tunisian prickly pears Opuntia ficus indica (spiny and thornless forms) and Opuntia stricta have been studied. The antioxidant capacity was measured by DPPH radical scavenging activity. The total phenolic compound (TPC) and the total flavonoid content were determined by the Folin–Ciocalteu method and colorimetric method, respectively. The phenolic compounds were identified and quantified by high-performance liquid chromatography (HPLC) coupled with an electrospray ionization mass spectrometry (ESI-MS). The results showed that O. stricta fruits present the best antioxidant activities than the two forms of O. ficus indica, while the TPC was more important in O. ficus indica than in the O. stricta fruits. The peels have higher flavonoids than pulp, and the thornless variety has more flavonoid than the spiny. The RP-HPLC and ESI-MS analysis detected two classes of phenolic compounds and betalain pigments. Isorhamnetin derivatives are the dominant flavonol glycoside identified in O. ficus indica (spiny: 65.25 μg·g−1; thornless: 77.03 μg·g−1) and O. stricta peels (19.22 μg·g−1). Antioxidants 2013-04-19 2 2 Article 10.3390/antiox2020037 37 51 2076-3921 2013-04-19 doi: 10.3390/antiox2020037 Nizar Yeddes Jamila Chérif Sylvain Guyot Hélène Sotin Malika Ayadi http://www.mdpi.com/2076-3921/2/1/23 Milk thistle dietary supplements that contain silymarin are widely marketed and used in the USA and other countries for liver enhancement and recovery. More recently, silymarin has also been identified as a possible antiviral for the treatment of hepatitis C virus (HCV) infection. To assess different brands of commercially sold silymarin, 45 products were collected from local stores and analyzed for their silymarin content, antioxidant activities, and antiviral activity against HCV. Antioxidant activity was measured as radical scavenging activity using DPPH and by estimating their antioxidant capacity as trolox equivalent. Anti-HCV activity was measured in an HCV genotype 1b replication inhibition assay. Samples were found to vary widely in their silymarin content, with some samples having none or very low concentrations while silymarin represented higher than 80% of other samples. Both antioxidant and anti-HCV activity correlated with the overall level of silymarin. Antioxidants 2013-02-06 2 1 Article 10.3390/antiox2010023 23 36 2076-3921 2013-02-06 doi: 10.3390/antiox2010023 Kevin Anthony Gitanjali Subramanya Susan Uprichard Faiza Hammouda Mahmoud Saleh http://www.mdpi.com/2076-3921/2/1/11 The main objective of this study was the screening of some selected aromatic plants very popular in Greece, with respect to their total phenolic content, antioxidant capacity, reducing activity, and oxidative stability. All plants were extracted with the conventional method, reflux with methanol. The essential oils of the plants were also analyzed for their antioxidant properties. The total phenolic content was determined by the Folin-Ciocalteu method using gallic acid as the standard, while the phenolic substances were identified and quantified by High Performance Liquid Chromatography (HPLC) coupled with a multi-wavelength ultraviolet-visible (UV-vis) detector. The antioxidant capacity of the plant extracts was measured by their ability to scavenge free radicals such as (a) DPPH (2,2-diphenyl-1-picrylhydrazyl) and, (b) ABTS (2,2′-azinobis-(3-ethylbenzothiaziline-6- sulfonate). The Folin-Ciocalteu method proved the existence of antioxidants in the aromatic plant extracts. Taking into account the results of the DPPH and ABTS methods, the free radical scavenging capacity was confirmed. Eventually, all plants exhibited low but noticeable protection levels against lipid oxidation, as determined by the Rancimat test. Antioxidants 2013-01-04 2 1 Article 10.3390/antiox2010011 11 22 2076-3921 2013-01-04 doi: 10.3390/antiox2010011 Charalampos Proestos Konstantina Lytoudi Olga Mavromelanidou Panagiotis Zoumpoulakis Vassileia Sinanoglou http://www.mdpi.com/2076-3921/2/1/1 Extracts of plants from the Malaysian rainforest and other fragile habitats are being researched intensively for identification of beneficial biological actions, with assessment of antioxidant behavior being a common component of such assessments. A number of tests for antioxidant behavior are used, with the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reduction activity potential (FRAP) assays often being used in parallel, and also with measurement of total phenolics content (TPC) as a surrogate marker for antioxidant capacity. The present study investigated the possible redundancy in using all three assays to determine antioxidant capacity in 92 extracts obtained from 27 plants from the Malaysian rainforest. The results demonstrated that the assays displayed a high (R ≥ 0.82) and significant (P < 0.0001) correlation with one another, indicating a high level of redundancy if all three assays are used in parallel. This appears to be a waste of potentially valuable plant extracts. Because of problems with the FRAP assay relating to color interference and variable rates of reaction point, the DPPH assay is the preferred assay in preliminary screening of extracts of plants from the Malaysian rainforest. Antioxidants 2013-01-04 2 1 Article 10.3390/antiox2010001 1 10 2076-3921 2013-01-04 doi: 10.3390/antiox2010001 Garry Clarke Kang Ting Christophe Wiart Jeffrey Fry http://www.mdpi.com/2076-3921/1/1/33 The antioxidant activity of four species of the Malvaceae family (Sidastrum micranthum (A. St.-Hil.) Fryxell, Wissadula periplocifolia (L.) C. Presl, Sida rhombifolia (L.) E. H. L and Herissantia crispa L. (Brizicky)) were studied using the total phenolic content, DPPH radical scavenging activity and Trolox equivalent antioxidant capacity (TEAC) assays. The antioxidant activity of the crude extract, phases and two isolated flavonoids, kaempferol 3,7-di-O-α-l-rhamnopyranoside (lespedin) and kaempferol 3-O-β-d-(6''-E-p-coumaroil) glucopyranoside (tiliroside) was determined. The results showed that there is a strong correlation between total polyphenol contents and antioxidant activity of the crude extract of Sidastrum micranthum and Wissadula periplocifolia; however, this was not observed between Sida rhombifolia and Herissantia crispa. The ethyl acetate (EaF) phase showed the best antioxidant effect in the total phenolics, DPPH and TEAC assays, followed by the chloroform (CfF) phase, in most species tested. Lespedin, isolated from the EaF phase of W. periplocifolia and H. crispa may not be responsible for the antioxidant activity due to its low antioxidant activity (IC50: DPPH: 1,019.92 ± 68.99 mg/mL; TEAC: 52.70 ± 0.47 mg/mL); whereas tiliroside, isolated from W. periplocifolia, H. crispa and S. micrantum presented a low IC50 value (1.63 ± 0.86 mg/mL) compared to ascorbic acid in the TEAC assay. Antioxidants 2012-10-26 1 1 Article 10.3390/antiox1010033 33 43 2076-3921 2012-10-26 doi: 10.3390/antiox1010033 Adriana Maria Fernandes de Oliveira Lilian Sousa Pinheiro Charlane Kelly Souto Pereira Wemerson Neves Matias Roosevelt Albuquerque Gomes Otemberg Souza Chaves Maria de Fátima Vanderlei de Souza Reinaldo Nóbrega de Almeida Temilce Simões de Assis http://www.mdpi.com/2076-3921/1/1/4 High rosmarinic acid (RA) productivity has been achieved by applying jasmonic acid and yeast extract elicitors to the in vitro sprout culture of Orthosiphon aritatus (IOSC). The highest RA accumulation from three solvents was detected in IOSC after treatment with yeast extract (5 g/L). HPLC analysis clearly confirmed a drastic increase in RA subjected to yeast extract elicitation. Therefore, this yeast extract elicited IOSC was chosen for a lactic acid bacteria (LAB) fermentation study as a model system. This selected IOSC was subjected to different types of LAB fermentations (Lactobacillus plantarum ATCC 8014 and Lactobacillus acidophilus NCFM) for different periods of time 24, 48 and 72 h. The LAB fermentations consisted of solid state fermentations (SSF) and liquid state fermentations (LSF) in a Digital Control Unit (DCU) fermenter system. The aim was to determine the effect of fermentation on the antioxidant properties of the plant extract. Results indicated that all types of LAB fermentation decreased the level of RA and total phenolics, however, a slight increase in total flavonoids and flavonols was observed in SSF samples. HPLC results confirmed that the longer the fermentation, the greater the reduction in RA content. The highest reduction was obtained in the sample of LSF inoculated with L. plantarum for a period of 72 h. The temperature of fermentation (37 °C) was predicted as contributing to the declining level in RA content. The loss in RA was concomitant with a loss of total antioxidant activity (1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity, Trolox Equivalent Antioxidant Capacity (TEAC), and Superoxide Dismutase (SOD)-like activity). These results indicate that RA is the major contributor to the antioxidant activity of this plant. Antioxidants 2012-09-26 1 1 Article 10.3390/antiox1010004 4 32 2076-3921 2012-09-26 doi: 10.3390/antiox1010004 Dase Hunaefi Divine N. Akumo Heidi Riedel Iryna Smetanska http://www.mdpi.com/2076-3921/1/1/1 Antioxidants, whether from diet or pharmacological supplementation, gained significant popularity among scientists and lay public in recent years, and was claimed to protect or treat numerous ailments. [...] Antioxidants 2012-09-25 1 1 Editorial 10.3390/antiox1010001 1 3 2076-3921 2012-09-25 doi: 10.3390/antiox1010001 Stanley Omaye Nabil Elsayed