Lipid characterization and antioxidant status of the seeds and meals of Camelina sativa and flax

Four different antioxidant activity assays including 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid (ABTS), 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP) and oxygen radical absorption capacity (ORAC), and thiobarbituric acid reactive substances were performed on the methanolic and ethyl acetate extracts of Camelina seeds (CS), flaxseeds (FS), Camelina meal low fat (CMLF, 9.9% fat), Camelina meal high fat (CMHF, 24.6% fat), and flaxseed meal (FSM, 2.7% fat). In addition, the fatty acid profile, and phenolic, tocopherol, flavonoid, and glucosinolate contents of CS, FS, CMLF, CMHF, and FSM were studied. The major fatty acid was α‐linolenic acid (C18:3 n‐3) which was 33.2, 29.4, 30.2, 60.1, and 39.3% in CS, CMLF, CMHF, FS, and FSM, respectively. The methanolic extract of CMLF showed the highest values of ABTS, DPPH and FRAP and the highest content of phenolic compounds, flavonoids, and glucosinolates. The methanolic and ethylacetate extracts of CMHF showed the highest values for ORAC and α‐ and γ‐tocopherols. The ethylacetate extracts of seeds and meals of Camelina sativa and flax showed lower values for antioxidant activity, phenolic compounds, and flavonoids than the methanolic extracts. In general, Camelina and FS meals showed higher antioxidant activities, and phenolic and flavonoid contents than their respective seeds. Practical applications: Camelina sativa seeds (CS) and flaxseeds (FS) are rich sources of omega 3 oils. Their by‐products after oil extraction are an attractive source of proteins, lipids, fiber, and natural bioactive compounds such as antioxidants. These by‐products may be used to improve nutritional value and prevent lipid oxidation in feed or food systems.     

Composition and Antioxidant Activity of Olive Leaf Extracts from Greek Olive Cultivars

The olive leaf phenolic composition of the Greek cultivars koroneiki, megaritiki and kalamon was determined using LC/MS. Furthermore, the antioxidant activity of olive leaf extracts from the above three cultivars, using solvents of increasing polarity (petroleum ether, dichloromethane, methanol and methanol/water: 60/40) was evaluated using the stable free radical diphenylpicrylhydrazyl (DPPH) test. Furthermore the oxidative stability index (OSI) was compared to that of the synthetic antioxidant TBHQ and commercial oleoresin (rosemary extract). The ability of phenolic compounds to inhibit the lipoxygenase (LOX) activity was also investigated. The ten main components determined in the olive tree leaf extracts for the cultivars koroneiki and kalamon were: secologanoside, dimethyloleuropein, oleuropein diglucoside, luteolin-7-O-glucoside, rutin, oleuropein, oleuroside, quercetin, ligstroside and verbascoside. Respective compounds for the cultivar megaritiki were: secologanoside, dimethyloleuropein, oleuropein diglucoside, luteolin7-O-glucoside, oleuropein, oleuroside, quercetin and ligstroside. In all three cultivars, oleuropein represented the main phenolic component. The solvent polarity influenced the total amount of the phenolic compounds determined. When methanol/water (60/40) was used, as solvent, more phenolic compounds were determined. The total amounts of phenols determined in the extracts, obtained by successive extractions using the above solvents, were 6,094, 5,579 and 6,196 mg/kg (mg gallic acid/kg dried olive leaves) for the cultivars megaritiki, kalamon and koroneiki, respectively. Among all extracts, methanol/water extracts exhibited the highest antioxidant activity as shown through the application of the DPPH and OSI methods. The OSI antioxidant activity followed the sequence: synthetic antioxidant TBHQ > commercial oleoresin > olive tree leaf extracts > control. Likewise, methanol/water olive leaf extracts significantly inhibited soybean lipoxygenase, although some small differences in the activity among the olive leaf extracts of the different cultivars were observed. The solvent polarity as well as the amount of the extract influenced the inhibitory activity. A positive correlation was shown between the antioxidant activity of leaf extracts and the total phenol content.     

Antioxidant activity of extracts from six different Sudanese plant materials

Methanolic extracts obtained by manual solvent extraction (MSE) and accelerated solvent extraction (ASE) of different Sudanese plant materials (Sclerocarya birrea leaves, Salvadora persica bark and leaves, Combretum hartmannianum leaves, Guiera senegalensis leaves and roots) were investigated for their antioxidant activity. There was no significant difference between the two extraction methods (p < 0.01) regarding the total amount of phenolic compounds expressed as gallic acid equivalents (GAE) (52.6–166.7 mg GAE/g total extractable compounds for MSE and 53.1–169.3 mg GAE/g for ASE). In comparison to a control without extract, the extracts were remarkably effective in the β‐carotene bleaching method, whereas the effectiveness was half or less in comparison to Trolox as standard antioxidant. Also using the 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) method antioxidant activity could be shown in comparison to a control, however, the extracts were less effective than Trolox. No significant difference was found between the two extraction methods. The increase of the peroxide value of sunflower oil during storage at 70°C was markedly lower after addition of the extracts in comparison to the control, but in the Rancimat test (120°C) the extracts showed only a small stabilization factor (F = 0.9–1.4) especially in comparison to Trolox (F = 5.8).     

Polyphenolic Contents and Antioxidant Potential of Stem Bark Extracts from Jatropha curcas (Linn)

We assessed the polyphenolic contents and antioxidant potential of the aqueous, ethanol and methanol stem bark extracts of Jatropha curcas. The total phenol, flavonoids, flavonols and proanthocyanidin contents of the extracts were evaluated to determine their effect on the antioxidant property of this plant, using standard phytochemical methods. The antioxidant and free radical scavenging activity of ethanol, methanol and aqueous extracts of the plant were also assessed against 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), ferric reducing, nitric oxide (NO), superoxide anion, (O(2) (-)) and hydrogen peroxide (H(2)O(2)) using spectroscopic methods and results were compared with that of butylated hydroxyl toluene (BHT) and ascorbic acid as standards. The concentrations of different classes of phenolic compounds were higher in methanol and ethanol extracts compared to aqueous extracts. There was correlation between total phenol, total flavonoids, total flavonol and total proanthocyanidins (r = 0.996, 0.978, 0.908, and 0.985) respectively. There was correlations between the amount of phenolic compounds and percentage inhibition of DPPH radicals scavenging activity of the extract (r = 0.98). Findings from the present study indicated that J. curcas is a potential source of natural antioxidants and may be a good candidate for pharmaceutical plant based products.     

Antioxidant activities of hot water extracts from various spices

Recently, the natural spices and herbs such as rosemary, oregano, and caraway have been used for the processing of meat products. This study investigates the antioxidant activity of 13 spices commonly used in meat processing plants. The hot water extracts were then used for evaluation of total phenolic content, total flavonoids content and antioxidant activities. Our results show that the hot water extract of oregano gave the highest extraction yield (41.33%) whereas mace (7.64%) gave the lowest. The DPPH radical scavenging ability of the spice extracts can be ranked against ascorbic acid in the order ascorbic acid > clove > thyme > rosemary > savory > oregano. The values for superoxide anion radical scavenging activities were in the order of marjoram > rosemary > oregano > cumin > savory > basil > thyme > fennel > coriander > ascorbic acid. When compared to ascorbic acid (48.72%), the hydroxyl radical scavenging activities of turmeric and mace were found to be higher (p < 0.001). Clove had the highest total phenolic content (108.28 μg catechin equivalent (CE)/g). The total flavonoid content of the spices varied from 324.08 μg quercetin equivalent (QE)/g for thyme to 3.38 μg QE/g for coriander. Our results indicate that hot water extract of several spices had a high antioxidant activity which is partly due to the phenolic and flavonoid compounds. This provides basic data, having implications for further development of processed food products.     

Antioxidant properties of polyphenol‐containing extract from soybean fermented with Saccharomyces cerevisiae

The antioxidant properties and total phenolic compounds of soybean extract fermented with Saccharomyces cerevisiae during 24 h were evaluated. Total polyphenolic compounds extracted in ethanol/water (1:1) solution were 789.54 mg/g dry extract, and flavonoids were 169.47 mg quercetin equivalents/g of dry extract. Reducing power (91.18%) and DPPH scavenging (79.30% at 4‐times diluted) were excellent, and so high as BHA, 92.17% and 73.8% respectively, while superoxide anion scavenging showed poor inhibition (4876 equivalent SOD U/g). Antioxidant activity in linoleic acid/water emulsion system of fermented extract measured as peroxide formation inhibition at 37 °C was the strongest (95.62%), while it exerted a moderate inhibition for conjugated dienes and thiobarbituric acid reactive substances (64.77% and 54.33%). At 80 °C the antioxidant activity assayed at a higher concentration was less effective (29.35% on CD; 74.58% on PV and 35.04% on TBARS).     

Evaluation of the effect of inner and outer bark extracts of sugar maple (Acer saccharum var. saccharum) in combination with citric acid against the growth of three common molds

The bark of trees is an abundant material for chemical by-products. The combination effects of different concentrations of Acer saccharum var. saccharum inner (IB) and outer (OB) bark acetone extracts with citric acid (CA) applied to Leucaena leucocephala wood were evaluated against the growth of three common molds (Trichoderma viride, Fusarium subglutinans, and Aspergillus niger). IB, OB, and CA solutions were prepared at 0.25% and 0.5% and their combinations were formulated in equal amounts. Acetone extracts of IB and OB were analyzed for their chemicals composition and phenolic compounds using GC/MS and PHLC, respectively. The IB acetone extract contained 4-hydroxy-4-methyl-2-pentanone (31.67%), palmitic acid (15.52%), and linoleic acid (11.14%), while the OB acetone extract contained 1,2-benzenedicarboxylic acid, bis(2-ethylhexyl) ester (9.34%), (Z,E)-9,12-tetradecadien-1-ol (8.86%), and cis-tetrahydro-6-methoxy-2H-pyran-3-ol (5.72%). The HPLC analysis indicated the presence of 14 phenolic compounds in IB extract with major constituents caffeine (362.88?µg/g extract), and p-hydroxy benzoic acid (358.06?µg/g extract), while OB contained 12 compounds with major constituents p-hydroxy benzoic acid (8950.5?µg/g extract), gallic acid (5261?µg/g extract) and salicylic acid (572.38?µg/g extract). High total phenolic content in OB (292.67?mg GAE/g) was associated with high antioxidant activity with an IC₅₀ values of 1.77 and 4.14?μg/mL, as measured by DPPH and β-Carotene-linoleic acid, respectively. The combination treatment of IB0.25%+ OB0.25%+CA0.25% produced the highest antifungal effects against growth of T. viride with an inhibition percentage (IP) of 10.37%, IB0.5%+CA0.5% (IP 16.66%) with F. subglutinans, while CA0.5% and OB0.25%, showed IP of 27.77% and 23.70% with A. niger, respectively. The combination effects of IB, OB and CA could be used as biocide agents for preventing mold growth on wood.     

Antioxidant properties of compounds isolated from wood vinegar by activity-guided and pH-gradient extraction

The chemical profile of wood vinegar (WV) was studied by gas chromatography-mass spectrometry (GC/MS), and 48 organic compounds were identified, including phenols which accounted for 2.0%. Antioxidant compounds were isolated from WV by an activity-guided isolation method for further investigation. The dichloromethane extract from WV exhibited the highest total phenolic content and demonstrated more potent antioxidant activity than the other extracts. Then, the phenols were enriched by pH gradient extraction method from the dichloromethane extract. Seven phenols were isolated from the WV using a sequence of column chromatographic purification steps over silica gel and C18 column, followed by semi-preparative HPLC and their structures were identified by ¹H NMR and ¹³C NMR spectra. All the compounds showed potent antioxidant activities in the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis (3-ethylbenzothiazoline- 6-sulphonic acid (ABTS), and ferric-reducing antioxidant power (FRAP) assays. This study demonstrates that phenols isolated from WV have the potential to be used as antioxidant agents.     

Evaluation of virgin olive oil bitterness by quantification of secoiridoid derivatives

The bitterness of the main compounds identified in the phenolic extract of virgin olive (Olea europaea L.) oils has been sensory-tested. The aldehydic form of oleuropein aglycone (AOA) was responsible for this attribute. Correlations between the sensory bitterness and concentrations of secoiridoid derivatives, analyzed separately or in different combinations, were obtained for olive oils from different olive varieties. The best correlation obtained corresponds to AOA content (r=0.96; P=1.83×10⁻¹⁷) in the concentration range of 0.03 to 0.5 mmol/kg. AOA concentrations ≥0.5 mmol/kg produce sensory saturation of this attribute. The correlation with AOA concentration was better than that with the absorbance of the phenolic extract at 225 nm. Therefore, the equation obtained allows the evaluation of the bitterness in virgin olive oils by HPLC analysis of the phenolic extract using detection at 280 nm.     

Effect of the Extraction Technique and Operational Conditions on the Recovery of Bioactive Compounds from Chestnut (Castanea sativa) Bur and Shell

The aim of this work was to study the extraction of phenolic compounds from chestnut bur and shell, both waste products of chestnut processing in the food industry. Two extraction techniques were compared—maceration with solvents and microwave-assisted extraction. The influence of the solvent used (water, 50% MeOH or 50% EtOH) and temperature (25-50-75°C) on extraction yield and extract total phenols content and FRAP, DPPH, and ABTS antioxidant activities was studied. In the conventional extraction, the yield was significantly higher for the bur (8.54–19.58%) than for the shell (2.91–13.27%); however, the shell extracts showed substantially greater properties. The best extract properties were achieved at 75°C using 50% MeOH for the bur and water for the shell and phenolic compounds with demonstrated antioxidant properties, as gallic acid esters of glucose and ellagic acid, were identified in these extracts by RP-HPLC-ESI-TOF. In addition, the aqueous extracts showed ability to inhibit the growth of gram positive and negative bacteria but not fungi. The kinetic of the extraction process was well fitted by the Peleg's model. The non-conventional microwave-assisted extraction slightly improved the chestnut bur extraction by reducing the extraction time.     

Radical scavenging activity of canola hull phenolics

Possible use of canola hulls as a source of natural anti-oxidants was explored. Cyclone canola hulls were extracted with methanol (30 to 80%, vol/vol) and acetone (30 to 80%, vol/vol). The free radical-scavenging activity of phenolic extracts so prepared was evaluated using the 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) radical ion (ABTS^o−), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, and chemiluminescence assays. The total content of phenolics in prepared extracts from canola hulls ranged from 15 to 136 mg sinapic acid equivalents per gram of extract. Higher levels of condensed tannins were detected in the acetone extracts than in the corresponding methanolic counterparts. Seventy and 80% (vol/vol) acetone extracts displayed markedly stronger antioxidant activity than any of the other extracts investigated. Statistically significant linear correlations were found between TEAC (Trolox equivalent antioxidant capacity) values (expressed in mM of Trolox equivalents per gram of extract) and total pehnolics, TEAC and total condensed tannins (i.e., determined using the modified vanillin and pronthocyanidin assays), as well as TEAC and protein precipitation activity of phenolic extracts (i.e., measured using the dye-labeled assay). The antioxidant activities of extracts as determined by the ABTS^o− radical ion assay correlated highly with those of the chemiluminescence and DPPH radical assays.     

光度法研究华芦荟叶的抗氧化活性

用不同溶剂对华芦荟叶进行超声提取,以标准抗氧化剂为对照,测定了提取液对自由基.OH和.DPPH的清除能力、铁还原能力,并采用IC50值对其抗氧化能力进行评价,实验结果表明,乙酸乙酯的提取液对.OH和.DPPH清除率均较高,其IC50值分别为4.41mg/ml dw,5.73 mg/ml dw。甲醇提取物的铁还原能力显示最高。分析华芦荟中黄酮或酚含量与FRAP的相关性,表明定华芦荟叶的抗氧化能力主要与酚含量相关。     

Oxidative stability of oils containing olive leaf extracts obtained by pressure,supercritical and solvent‐extraction

The effect of the addition of olive leaf (Olea europaea, cv. Arbequina) extracts, i.e. hydroalcoholic (ethanol–water 1:1; OHE), juice (OJ) and supercritical fluid‐CO₂ (OSFE) on the oxidative stability of vegetable oils with different unsaturation, such as soybean oil (SBO), canola oil (CO) and high oleic sunflower oil (HOSO), were studied at two concentrations (250 and 630 mg/kg oil, expressed as caffeic acid equivalent (CAE)). The extracts were characterized by the total phenolic content (Folin–Ciocalteau method), phenol chromatographic profiles (LC‐MS) and antioxidant activity (DPPH). OHE showed the highest phenol content (7.7 mg CAE/mL) while OJ and OSFE showed values of 5.4 and 2.2 mg CAE/mL, respectively. Oleuropein and its derivatives were the major phenolic compounds identified in OHE. The addition of 630 mg CAE/kg oil of OHE and OSFE to HOSO, SBO and CO showed an antioxidant effect, increasing significantly the induction time (IT) (p<0.05). That effect was highest when the system was more monounsaturated. In contrast, OJ showed a pro‐oxidant effect for all oils systems for both concentration studied. This behaviour could be attributed to the diphenol oxidase (PPO) activity.     

Chemical Characterization of the Seed and Antioxidant Activity of Various Parts of <Emphasis Type="Italic">Salvadora persica</Emphasis>

This study investigated the fatty acid, tocopherol, sterol and total phenolic compounds of Salvadora percica seeds as well as the potential antioxidant activity of the leaves, bark and seedcake extracts. Two samples of S. persica seed collected from Kordofan (sandy soil) and Gezira (heavy clay soil) states in Sudan were used. The predominant fatty acids were 14:0, 16:0 and 18:1 representing 45.50, 35.12 and 10.20% for Kordofan and 45.20, 34.49 and 10.66% for Gezira samples. Gamma-tocopherol was the predominant tocopherol in both samples representing 61.3 and 61.7% of the total tocopherols, respectively, followed by α-tocopherol at 21.1 and 20.2%, respectively. Total sterol content was 3399.6 and 3385.3 mg/kg for Kordofan and Gezira samples, respectively. Beta-sitosterol, campesterol, stigmasterol and Δ5-avenasterol were predominant. The content of total phenolic compounds was determined in S. persica bark (SPB), S. persica leaves (SPL), and S. persica seedcake (SPC) extracts of each sample according to the Folin–Ciocalteau method as 111.70, 132.60, and 66.10 mg GAE/g extract for the Kordofan sample. They were found to be 105.90, 129.10 and 62.90 mg GAE/g extract in the Gezira sample, respectively. The two samples were significantly (P < 0.05) different in total phenolic content with SPL as the highest in both samples. The methanolic extracts of SPL, SPB, and SPC in both samples were markedly effective in inhibiting the oxidation of linoleic acid and subsequent bleaching of β-carotene in comparison with the control. But they were less effective than butylated hydroxyanisole.     

Evaluation of natural and synthetic compounds according to their antioxidant activity using a multivariate approach

The antioxidant activity of natural and synthetic compounds was evaluated using five in vitro methods: ferric reducing/antioxidant power (FRAP), 2,2‐diphenyl‐1‐picrylhydradzyl (DPPH), oxygen radical absorption capacity (ORAC), oxidation of an aqueous dispersion of linoleic acid accelerated by azo‐initiators (LAOX), and oxidation of a meat homogenate submitted to a thermal treatment (TBARS). All results were expressed as Trolox equivalents. The application of multivariate statistical techniques suggested that the phenolic compounds (caffeic acid, carnosic acid, genistein and resveratrol), beyond their high antioxidant activity measured by the DPPH, FRAP and TBARS methods, showed the highest ability to react with the radicals in the ORAC methodology, compared to the other compounds evaluated in this study (ascorbic acid, erythorbate, tocopherol, BHT, Trolox, tryptophan, citric acid, EDTA, glutathione, lecithin, methionine and tyrosine). This property was significantly correlated with the number of phenolic rings and catecholic structure present in the molecule. Based on a multivariate analysis, it is possible to select compounds from different clusters and explore their antioxidant activity interactions in food products.     

Antioxidant activity of crude tannins of canola and rapeseed hulls

The antioxidant activity of crude tannins of canola and rapeseed hulls was evaluated by β-carotene-linoleate, α,α-diphenyl-β-picrylhydrazyl (DPPH) radical, and reducing power assays. Crude tannins were extracted from three samples of Cyclone canola (high-tannin) hulls and Kolner, Ligaret, and Leo Polish rapeseed (low-tannin) hulls with 70% (vol/vol) acetone. The total phenolic content in crude tannin extracts ranged between 128 and 296 mg of sinapic acid equivalents per 1 g of extract. The ultraviolet spectra of methanolic solution of canola extracts showed two absorption maxima (282 and 309 nm), whereas those of rapeseed extracts exhibited a single maximum (326 nm). Crude tannins isolated from canola hulls exerted significantly (P<0.025) greater antioxidant activity than those from rapeseed in all three assays. The scavenging effect of all crude tannins, at a dose of 1 mg, on the DPPH radical ranged from 35.2 to 50.5%. The reducing power of Cyclone canola hull extracts on potassium ferricyanide was significantly (P≤0.0025) greater than that of rapeseed hull extracts, and the observed data correlated well (r=0.966; P=0.002) with the total content of phenolics present.     

Screening the Antioxidant and Antimicrobial Properties of the Extracts from Plantain (Plantago Major L.) Leaves

Abstract

Antioxidant and antimicrobial activities of the extracts obtained by classical (maceration) and ultrasonic (40 kHz) extraction from dry Plantago major leaves were compared. The antioxidant activities of extracts obtained by ultrasonic and classical extraction were 0.87±0.02 and 0.85±0.02 µg/µg DPPH, respectively. Ultrasound positively affected the extractive substance yield and the kinetics of extraction, but the extract obtained by classical extraction contained higher total contents of phenolic compounds and flavonoids than that obtained by ultrasonic extraction. Extracts of P. major showed better antimicrobial activity against the yeasts than against the bacteria.     

Primary Metabolites and Polyphenols in Rapeseed (Brassica napus L.) Cultivars in China

Defatted meals of 10 rapeseed (Brassica napus L.) varieties were investigated for their total phenolic, phenolic acid (free, esterified, and insoluble-bound forms), and tannin contents. The antioxidant capacities (AC) of methanol extracts from samples were assessed using the 2,2′-diphenyl-1-picrylhydrazyl radical (DPPH•), Folin–Ciocalteu method and ferric reducing antioxidant power (FRAP), and β-carotene–linoleic acid tests. In the fraction of free phenolic acids, sinapic, caffeic, ferulic, syringic, gallic, and p-coumaric acids were identified. In the fraction of esterified phenolic acids, sinapine, sinapoyl glucoside, and disinapoyl gentiobiose were identified. After basic hydrolysis, sinapic, ferulic, cinnamic, and 4-hydroxybenzoic acids were identified, and sinapic acid (SA) constituted 98.3% to 99.6% of the total esterified phenolic acids. Eleven components (sinapic, protocatechuic, p-coumaric, syringic, vanillic, gallic, caffeic, ferulic, salicylic, cinnamic, and 4-hydroxybenzoic acids) in the fraction of insoluble-bound phenolic acids were identified. The AC of the samples correlated with the total phenolic content. Overall, the total phenolics showed a better correlation with AC than the individual phenolic compounds. Moreover, SA, sinapoyl glucoside, and disinapoyl gentiobiose showed a highly significant and strong positive correlation with the AC of rapeseed meals, and the derivatives of cinnamic acid showed a higher correlation with AC than the derivatives of benzoic acid. The change in the canolol content in rapeseeds under microwave irradiation is discussed. The correlation of the canolol formed with SA and its derivatives is discussed.     

Distribution and Antioxidant Activities of Free,Conjugated, and Insoluble-Bound Phenolics from Seven Species of the Genus Camellia

Free phenolic (FP), conjugated phenolic (CP), and insoluble-bound phenolic (IBP) acids were extracted from the seeds of seven species of oil-tea camellia and their antioxidant activities were evaluated. The results indicated that Camellia vietnamensis has the highest total phenolic content (TPC) (31.84 ± 0.11 g of gallic acid equivalent [GAE] kg⁻¹) and that Camellia polyodontia has the lowest TPC (12.34 ± 0.22 g GAE kg⁻¹) in the kernel. The average TPC among the species is similar in both the kernels and in the shells, and the content order of the three forms of phenolic compounds is FP > IBP > CP. HPLC-MS analysis showed the presence of 9–11 phenolic compounds in the FP, CP, or IBP extracts of the seven species of oil-tea camellia seed. Among the phenolics identified, ferulic acid, catechin, and epicatechin were the major contributors of antioxidant activity. Hierarchical cluster analysis conducted based on the phenolic properties showed that C. vietnamensis and Camellia semiserrata belong to the group characterized by high antioxidant capacities (FRAP, ferric-ion-reducing antioxidant power; ABTS assay), and Camellia chekiangoleosa and Camellia oleifera are arranged in a group with moderate phenolic properties. The other species constitute the third cluster with low phenolic content and antioxidant activity. The study demonstrated that oil-tea camellia seed contains significant amounts of phenolic acids. In addition, extracts from various parts of the seed could be interesting novel sources of natural antioxidants.     

Selection of Natural Extracts for their Antioxidant Capacity by Using a Combination of In Vitro Assays

Numerous different in vitro assays, labeled as “antioxidant assays,” are used intensively to predict the antioxidant capacity of phenolic compounds. Most of these methods give valuable information in terms of chemical reactivities but also present some weaknesses. It may be difficult to use them to predict antioxidant capacity in real conditions. Indeed, lipid oxidation is a complex reaction, with numerous paths and components, and antioxidant action can occur via a multitude of mechanisms, especially when different phases coexist in the lipid-based formulation. Yet, correctly combining selected in vitro methods to extract complementary information with respect to antioxidant behaviors would be much better and will help reducing the gap between prediction and efficacy in the finished product. Thus, we hereby propose a methodology to evaluate the antioxidant properties of 12 selected natural polyphenolic extracts based on the appropriate combination of in vitro assays. The scores obtained with the DPPH test, the measure of the chelation capacity, the evaluation of antioxidants efficiency in emulsions (CAT and VESICAT assays), or in bulk oils were submitted to a statistical treatment. This analysis allowed a ranking on their global antioxidant capacities and the creation of clusters depending on their mechanisms of action and the type of media where the tests were performed.