Antioxidant activities of selected oriental herb extracts

Antioxidant activities of methanol extracts of 180 Oriental herbs were studied by determining the peroxide values of linoleic acid during storage at 50°C. Among the herb extracts tested, 44 species showed strong antioxidant activities on the oxidation of linoleic acid. The antioxidative effects of these 44 selected herb extracts were studied further in a methyl linoleate system during storage for 35 d. Among the 44 species tested, 11 species had particularly high antioxidative effects. The effects of type of extraction solvent (methanol, petroleum ether and ethyl acetate) on the antioxidant activities of the 11 species were studied. Antioxidant activities of most herb extracts were greatly dependent on the extraction solvent used; however, some of the extracts showed strong antioxidant activities regardless of the solvents used for the extraction. Among the 11 herbs selected, based on the antioxidant activity of their methanol extracts, two (i.e.,Psoralea corylifolia L. andSorphora angustifolia Sieb. & Zucc.) were selected for further study in lard held at 75°C for 7 d. The methanol extracts ofP. corylifolia L. andS. angustifolia Sieb. & Zucc. greatly decreased the peroxide formation of lard during storage. Treatment with 0.20% methanolic extract ofP. corylifolia L. exhibited significantly stronger antioxidant effect on the oxidation of lard than treatment with 0.02% butylated hydroxyanisole (P<0.05).     

Response Surface Optimized Ultrasonic-Assisted Extraction of Quercetin and Isolation of Phenolic Compounds From Hypericum perforatum L. by Column Chromatography

The effects of ultrasonic-assisted extraction factors for the main phenolic compound (quercetin) from Hypericum perforatum L. were optimized using the Box–Behnken design (BBD) combined with response surface methodology. The BBD was employed to evaluate the effects of extraction temperature (30–70°C), extraction time (20–80 min), methanol concentration (20–80%, v/v), and HCl concentration (0.8–2.0 M) on the content of one of the major phenolic compounds of quercetin. The extracts were analyzed by high performance liquid chromatography (HPLC). The major phenolic compounds of H. perforatum were isolated and the antioxidant capacity and total phenol content were determined in crude extract and fractions. The optimum conditions were determined as extraction temperature 67°C, extraction time 67 min, methanol concentration 77% (v/v), and HCl concentration 1.2 M. The predicted content of quercetin was 10.81 mg/g dried plant under the optimal conditions and the subsequent verification experiment with 11.09 mg/g dried plant confirmed the validity of the predicted model. The isolated compounds were identified as quercetin, cyanidin, protocatechuic acid, and kaempferol.     

Flavonoids released by carrot (Daucus carota) seedlings stimulate hyphal development of vesicular-arbuscular mycorrhizal fungi in the presence of optimal CO2 enrichment

Carbon dioxide has been previously identified as a critical volatile factor that stimulates hyphal growth ofGigaspora margarita, a vesiculararbuscular mycorrhizal fungus, and we determined the optimal concentration at 2.0%. The beneficial effect of CO₂ on fungal development is also visible in the presence of stimulatory (quercetin, myricetin) or inhibitory (naringenin) flavonoids. Sterile root exudates from carrot seedlings stimulate the hyphal development ofG. margarita in the presence of optimal CO₂ enrichment. Three flavonols (quercetin, kaempferol, rutin or quercetin 3-rutinoside) and two flavones (apigenin, luteolin) were identified in carrot root exudates by means of HPLC retention time. Flavonols like quercetin and kaempferol are known to have stimulatory effects on hyphal growth ofG. margarita.     

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).     

Flavonoids as stabilizers of fish oil: An alternative to synthetic antioxidants

The antioxidant activities against fish oil oxidation of six commercially available flavonoids and of five flavonoids purified from two Chilean native plants were compared to those ofdl-α-tocopherol and of two synthetic antioxidants, butylated hydroxytoluene and butylated hydroxyanisole. Among the commercial flavonoids, catechin, morin and quercetin showed a higher activity when fish oil oxidation (either spontaneous or Fe²⁺-induced) was assessed from the formation of peroxides or thiobarbituric acid-reactive substances. Among the native flavonoids, the 5,3′,4′-trihydroxy-7-methoxy flavanone (designated as Pt-2) showed the highest antioxidant activity. Mixtures of quercetin or of Pt-2 withdl-α-tocopherol produced better inhibitory effects when compared to that of each substance assayed by itself. Also, when Pt-2 and quercetin were assayed in combination (0.3 g/kg oil and 0.7 g/kg oil, respectively), a synergistic antioxidant effect was observed. Results indicate that several flavonoids could be used as natural antioxidants as a means to replace those synthetic antioxidants, the use of which has been questioned.     

Stoichiometric and kinetic studies on Ginkgo biloba extract and related antioxidants

Owing to increasing evidence showing the importance of lipid peroxidation in oxidative stress in vivo, the role and evaluation of antioxidants have received much attention. Ginkgo biloba extract (GBE), well-known as an efficient drug against diseases induced by free radicals, has been suggested to exert its effect by antioxidant action. A method was established to determine the activity of GBE as a hydrogen donor by stoichiometric and kinetic studies, and GBE was compared with several other antioxidants such as α-tocopherol, propyl gallate, and two kinds of flavonoids which are found in GBE, quercetin, and kaempferol. It was found that there were 6.62×10¹⁹ active hydrogens in 1g of GBE. Stoichiometric studies showed that one molecule of α-tocopherol reacted with one molecule of galvinoxyl radical. For quercetin, kaempferol and propyl gallate, the experimental stoichiometric numbers were 4.0, 1.9, and 3.1, respectively. The rates of reaction of antioxidants with galvinoxyl in ethanol were determined spectrophotometrically, using a stopped-flow technique. The second-order rate constant, k ₂, obtained at 25°C was 0.13 (g/l)⁻¹s⁻¹ for GBE and 5.9×10³, 2.1×10³, 1.2×10⁴, and 2.4×10³ M⁻¹s⁻¹ for quercetin, kaempferol, propyl gallate, and α-tocopherol, respectively. The second-order rate constant, k ₂′, on the molar basis of active hydroxyl groups in the tested substances obtained at 25°C decreased in the order of propyl gallate > α-tocopherol> quercetin>GBF∼kaempferol. This is the first study on GBE as an antioxidant which reports both stoichiometric and kinetic results.     

Management of Surface Drying Temperature to Increase Antioxidant Capacity of Thyme Leaf Extracts (Thymus vulgaris L.)

Thyme leaves are an important source of essential oils with antioxidant activity; these compounds are located in trichomes on the leaf surface. The drying conditions affect not only the drying time but also the antioxidant activity. In the literature, a drying temperature of 70°C appears to be the best for drying thyme leaves according to their antioxidant capacity. Considering drying periods at different temperatures also could be beneficial. With these considerations, the goal of this work was to establish a drying strategy with which to manage a drying temperature on the leaf surface that will enable the drying time to be shortened and improve the antioxidant capacity (AC) of the extract of dried thyme leaves. The drying strategy consisted of two consecutive drying periods in order to manage the drying temperature on the leaf surface. The first drying period was carried out at 80°C (T _a1) until the sample surface reached a temperature of 70°C, and the temperature was then immediately set to 70, 60, 50, and 40°C (second drying period, T _a2) at different air velocities (v; 1 and 2 m s^?1). Compared to constant drying conditions, two consecutive drying periods were found to improve the drying kinetics: the AC increased from 10.5 to 27.4% while reducing the drying time by 14.5 to 39.2%. The use of this drying strategy was found to be an interesting means of intensifying the convective drying of thyme leaves and its application should be considered when drying similar materials with bioactive compounds on the surface.     

Chia seeds as a source of natural lipid antioxidants

Chia (Salvia sp) seeds were investigated as a source of natural lipid antioxidants. Methanolic and aqueous extracts of defatted chia seeds possessed potent antioxidant activity. Analysis of 2 batches of chia-seed oils demonstrated marked difference in the fatty acid composition of the oils. In both batches, the oils had high concentrations of polyunsaturated fatty acids. The major antioxidant activity in the nonhydrolyzed extract was caused by flavonol glycosides, chlorogenic acid (7.1 × 10⁻⁴ mol/kg of seed) and caffeic acid (6.6 × 10⁻³ m/kg). Major antioxidants of the hydrolyzed extracts were flavonol aglycones/kaempferol (1.1 × 10⁻³ m/kg), quercetin (2.0 × 10⁻⁴ m/kg) and myricetin (3.1 × 10⁻³ m/kg); and caffeic acid (1.35 × 10⁻² m/kg). Two methods were used to measure antioxidant activities. Both were based on measuring bleaching ofβ-carotene in the coupled oxidation ofβ-carotene and linoleic acid in the presence of added antioxidants.     

Antioxidant Activity of Rambutan (Nephelium lappaceum L.) Peel Extract in Soybean Oil during Storage and Deep Frying

Rambutan (Nephelium lappaceum L.) peel (RBP) is discarded as the main by‐product during processing of the fruit. Increasing attention is now paid to the valorization of RBP for the recovery of valuable compounds. Geraniin, ellagic acid, quercetin, and rutin are the main phenolic compounds found in methanolic RBP extract. Extracted rambutan peel powder (ERPP) is used to evaluate the oxidative stability of soybean oil stored at 4 and 30 °C in the dark and light and deep fried with potatoes at 160 °C. Tert‐butylhydroquinone (100 µg g^?1 oil, TBHQ) serves as positive control. Oil supplemented with ERPP of 1000 µg gallic acid equivalents (GAE) g^?1 of oil shows positive effects on the retardation of the oxidation process during storage in comparison with oil without addition. During deep frying, either ERPP (1000 µg GAE g^?1) or TBHQ retards the lipid oxidation of oil. Levels of thiobarbituric acid reactive substances of potatoes fried in oil fortified with the extract and TBHQ (0.4–0.59 µg g^?1) are much lower than those without the extract (1.31 ± 0.10 µg g^?1) (p < 0.05). Therefore, RBP extract exhibits favorable antioxidant effects and can be used for effectively inhibiting lipid oxidation in oil during storage and deep frying. Practical Applications: An extract from rambutan fruit peel containing phenolic compounds, that is, geraniin, ellagic acid, rutin, and quercetin showed promising results to be used as potential antioxidants in soybean oil during deep frying. Both oxidation of the frying oil as well as the oxidation of the food product, that is, potatoes were inhibited. These results demonstrated that rambutan fruit peel extract can be used as a natural antioxidant in frying oil to replace synthetic antioxidants, that is, TBHQ.     

Antioxidant Activities of Free and Liposome-Encapsulated Green tea extracts on canola oil oxidation stability

In the present study, green tea extract was encapsulated in liposomes based on the Mozafari method (with no organic solvents) and characterized for its physicochemical properties (encapsulation efficiency, particle size, and Z-potential). Encapsulation efficiency, particles size, and Z-potential were determined to be 51.34, 419 nm, and -57 mV, respectively. Total polyphenol content of the green tea by Folin-Ciocalteu's phenol reagent was measured as 164.2 mg gallic acid/g extract. Free radical scavenging activities of free and liposomal extracts were 90.6 and 93.4%, respectively, using the DPPH method. Antioxidant activity of the ethanolic extract of green tea in free and liposomal forms with concentrations of 200, 600, and 1000 mg L⁻¹ were assessed on oxidative stability of the canola oil at 60 °C for 0, 4, 8, 12, 16, 20, 24, 28, and 32 days. Results were compared to results of synthetic antioxidant butylated hydroxytoluene at 200 mg L⁻¹. To assess antioxidant activity on canola oil stability, peroxide, thiobarbitoric acid, and anisidine values were assessed as well as the total oxidation value and rancimat test. Results showed that the liposomal green tea extract was more effective than the free extract. Furthermore, a 600 mg L⁻¹ concentration of the green tea extract showed a significant antioxidant activity, compared to other extract concentrations. Increasing storage time and various concentrations of the ethanolic green tea extracts included significant effects on canola oil stability (P ≤ 0.05). Results demonstrated that the green tea extract could be used as an effective antioxidant. Free and liposomal extract (at 600 mg L⁻¹) resulted in stronger functionality than the synthetic antioxidant butylated hydroxytoluene.     

Partial purification and characterization of acylester hydrolase from Lupinus mutabilis

An alkaline acylester hydrolase was partially purified from germinated seeds of Lupinus mutabilis. Hydrolytic activity was absent in the crude extract of ungerminated lupine seed, but it increased and peaked at the fourth day in the germinating seedling. The purification scheme involved homogenization, centrifugation, acetone precipitation, anion exchange chromatography, pH precipitation, and hydrophobic interaction chromatography. The acylester hydrolase was purified 126-fold, and the overall activity yield was 10%. The molecular weight estimated by sodium dodecylsulfate-polyacrylamide gel electrophoresis was 60 kDa. The enzyme had an isoelectric point of 6.2 and showed maximal activity at pH 8.0. The enzyme showed good stability between pH 5.0 and 9.0. In the pH range 7.0–7.5, enzyme precipitation was observed. The enzyme was stable from 0 to 25°C for 5 h and at 45°C lost 50% of its activity in the same period of time. At higher temperatures, the enzyme showed low thermal stability. However, the highest initial activity was found to be at 45°C. Nonionic surfactants and cholic acid enhanced the activity of the enzyme. The activity was reduced by the addition of toluene and isooctane and increased by the addition of diethyl ether, acetonitrile, methanol, and pyridine. The activity was reduced by 37% in the presence of 1 mM Cu²⁺ ions. The enzyme-hydrolyzed triolein showing no positional specificity.     

The kinetics of hydrolysis ofNigella sativa (black cumin) seed oil catalyzed by native lipase in ground seed

Kinetics of the lipolysis ofNigella sativa oil catalyzed by native lipase in crushed seed were studied between 20 and 90°C. Data fitted the pseudo first-order rate equation at 20, 30 and 40°C; and the pseudo second-order equation at 50, 60 and 70°C, but neither equation fit at 80 and 90°C. Lipolysis approximated first-order with respect to water.     

Biosynthesis of Quercetin Palmitate Esters and Evaluation of their Physico-Chemical Properties and Stability

Quercetin was acylated with palmitic acid, catalyzed by either Candida antarctica lipase B (CAL-B) or Pseudomonas cepacia lipase C (PCL-C) to produce quercetin palmitate esters. The effects of various operating factors including incubation temperature, reaction duration, and molar ratio of substrates on the bioconversion yield, initial rate of reaction, and regioselectivity of the reactions were investigated. Three new esters were identified: quercetin 4′-palmitate (C₃₁H₄₀O₈, 540 g mol⁻¹), quercetin 3′,4′-dipalmitate (C₄₇H₇₀O₉, 778 g mol⁻¹), and quercetin 7,3′,4′-tripalmitate (C₆₃H₁₀₀O₁₀, 1016 g mol⁻¹). The effects of incubation temperature, reaction duration, and molar ratio of substrates on bioconversion yields varied across the conditions. However, the highest bioconversion yield of 27.72 ± 1.64% was obtained with PCL-C, at day 7, incubation temperature of 60 °C, quercetin:palmitic acid molar ratio of 1:20. The initial rate of reaction was significantly higher with PCL-C. However, regioselectivity was similar for both PCL-C- and CAL-B-catalyzed reactions with acylation occurred successively at 4´-OH, 3´-OH, and 7-OH. Thin-layer chromatography analysis showed that the three quercetin palmitate esters possessed enhanced lipophilicity (134% higher than quercetin). Besides, in silico investigation showed that quercetin 4′-palmitate had a higher partition coefficient (log P) value than the parent compounds, indicating improved solubility. During gastrointestinal tract simulation, quercetin palmitate esters were recovered in the range of 71.03% to 79.36% after digestion, which were significantly higher than quercetin at 40.43 ± 8.71%. Quercetin 4′-palmitate was also found stable over 28 days of storage. Due to improved lipophilicity, solubility, and stability, quercetin 4′-palmitate has the potential to be used in topical applications.     

Purification and characterization of a thermophilic chitinase produced by <Emphasis Type="Italic">Aeromonas</Emphasis> sp. DYU-Too7

An extracellular chitinase, produced by Aeromonas sp. DYU-Too7, was purified in the following procedures: ammonium sulfate precipitation, ultrafiltration, chromatographic separation of DEAE-sepharose CL-6B and sephacrylS-100HR. The resulting chitinase has a molecular mass of 36 kDa, an optimal reaction pH of 5.0, and an optimal reaction temperature of 70°C. It retains almost 100% activity in the pH range of 5.0–8.0. This chitinase has a high thermal tolerance and retained 90% of its activity at 50°C and 75% at 60°C. Enzyme activity was inhibited by Ba²⁺, Hg²⁺, Mg²⁺ and Ag⁺ cations, but was not substantially inhibited by the K⁺ cation nor the chelating agent EDTA. The K _m and V _mα , using colloidal chitin as a substrate, are 6.3 g/L and 18.69 μmol/min/mg-protein, respectively. The 36 kDa chitinase of Aeromonas sp. DYU-Too7 is an exo-type enzyme, because chitobiose was the main hydrolysate in hydrolysis of colloidal chitin.     

Effect of temperature and chainlength on the densities and molal volumes ofn-alkyl chlorides

The densities ofn-alkyl chlorides from pentyl chloride to hexadecyl chloride were determined at temperatures between 15–80°C at 5°C intervals. The densities increase linearly with temperature and chainlength. A four-constant equation, V=n/(−3.6640 × 10⁻⁵ T+0.07151)+1/(−5.6526 × 10⁻⁵ T+0.04243), was formulated. This formula accurately predicted the molal volume and, hence, the density for all then-alkyl chlorides at any temperature within the range.     

Chemical composition and antioxidant activity of extracts from <Emphasis Type="Italic">Daphne gnidium</Emphasis> L.

Members of the Daphne genus have been of interest owing to their excellent medicinal value. In this work, we describe the results of phytochemical analysis and the antioxidant activity of the methanol extracts from leaves and stems of D. gnidium L. grown wild in Sardinia, Italy. Four coumarins (daphnetin, daphnin, acetylumbelliferon, and daphnoretin), nine flavonoids (apigenin, luteolin, quercetin, orientin, isoorientin, luteolin 7-O-glucoside, apigenin 7-O-glucoside, genkwanin, and 5-O-β-d-primeverosyl genkwanine), and α-tocopherol were isolated. We investigated the ability of the two extracts and five pure compounds (daphnetin, daphnoretin, apigenin, luteolin, and α-tocopherol) to protect linoleic acid against free radical attack in simple in vitro systems by autoxidation and iron- or EDTA-mediated oxidation. Pure compounds were the most active antioxidants. During autoxidation, daphnetin, luteolin, and α-tocopherol were effective at a molar ratio of 1∶1600, 1∶2500, and 1∶2000, respectively. Daphnoretin was active only at high concentrations. During the iron-catalyzed oxidation of linoleic acid, all the materials tested showed activity in the following order: luteolin>daphnetin>α-tocopherol >leaf extract>stem extract>daphnoretin. Apigenin was not active in any of the experimental systems used.     

Antioxidant properties of myricetin and quercetin in oil and emulsions

The effect of quercetin and myricetin on the stability of sunflower oil and oil-in-water emulsions was studied by storage experiments monitored by measurement of peroxide values, conjugated dienes, and headspace volatile analysis. Myricetin showed strong antioxidant activity in oils stored at 60 or 30°C and in oil-in-water emulsions stored at 30°C, whether tocopherols or citric acid were present or not; however, quercetin showed similar antioxidant activity in stripped sunflower oil but no activity in oils that contained tocopherols and citric acid. This showed that myricetin is effective owing to strong radical scavenging and metal-chelating properties, whereas quercetin has weaker radical scavenging activity, although it is also active by metal-chelation. The effects of copper and iron salts on the antioxidant activity of myricetin and quercetin were studied in sunflower oil and oil-in-water emulsions. Quercetin and myricetin enhanced the prooxidant effect of cupric chloride in oil-in-water emulsions (pH 7.4), but this effect was not observed with cupric stearate. The addition of myricetin to emulsions that contained ferric chloride at pH 5.4 also produced a strong prooxidant effect, and small prooxidant effects of flavonols were also detected in the presence of cupric chloride under these conditions. However, myricetin and quercetin reduced the prooxidant effect of ferric palmitate in oils. Myricetin also showed a strong antioxidant effect in oil that contained cupric stearate, although quercetin had no significant effect on the oxidative stability of this system. It therefore appears that flavonols may exert a prooxidant effect in the presence of metal salts, but the nature of the metal salt is important in determining whether a prooxidant effect occurs.     

Antioxidant activity of tea extracts in lipids and correlation with polyphenol content

The present study examined the antioxidative activity of water and ethanol extracts of green and black tea leaves against the oxidation of heated sunflower oil and lard. Oxidation was conducted at 110 °C in the Rancimat test. Total polyphenols and catechin contents in tea extracts were measured. The research showed that the total polyphenol content in green and black tea leaves was 205.2 and 148.7 mg/g, respectively. In tea leaves extracts, it ranged between 245.9 mg/g and 837.7 mg/g and depended on the extraction solvent and the kind of tea used (p <0.001). The highest polyphenol content was observed in samples extracted with 95% ethanol, lower contents were found with the use of water. Results showed that the highest antioxidant activity, measured as an induction period, with 1000 ppm green tea ethanol extract, was comparable to á‐tocopherol activity in sunflower oil. In lard, the longest induction period was measured with 500 and 1000 ppm of green tea ethanol extract. Other tea extract concentrations were significantly less active. Statistical analysis of the tea extract antioxidant activity in lipids in the Rancimat test showed an essential influence of the catechin contents. Further statistical analysis also showed an influence of (?)‐epicatechin gallate (ECG), (?)‐epicatechin (EC), and (+)‐catechin (C) contents in the tea extracts on the antioxidant activity in lipids. It was stated that the antioxidant activity was higher in tea extracts containing high levels of ECG, EC, and C.     

Antioxidative Wirkung von Pflanzenextrakten auf Futterfette

Antioxidative Activity of Extracts of Plants on Feed Fats The antioxidative activity of ethanol extract from unripe Madura-fruits (Madura aurantiaca) Nutt./Osage orange) as well as extracts from overground plant parts was investigated. Tallow and lard (prepared by wet procedure) at 60° C and in Rancimat apparatus were used as substrates. The comparison was made with BHA as synthetic antioxidant. The plant extracts from Asclepias syriaca L. (sample A), Chenopodium ambrosiodes L. (sample B). Thymus marschallianus Willd, (sample C) showed only a moderate antioxidative activity with substrates tempered to 60^OC. which was not confirmed by the results obtained with Rancimat apparatus. The extract of unripe Maclura-fruits shows a very strong antioxidative activity, which is comparable with pure BHA and extends inductive period at applied substrates many times. The addition of citric and malic acid shows synergetic effect. Additionally, the experiments were made with application of pulver of unripe Maclura-fruits. The use of 0.1 -0.2% of this pulver at applied substrates (tallow, lard, heated to 60⁰Cj induces a very high prolongation of induction period, similar as by 0.01 % BHA. The measurements with Rancimat apparatus showed the same relations of prolongation of induction period of substrates for application of extract or pulver of Maclura-fruits.     

Antioxidants from a heated histidine-glucose model system. I: Investigation of the antioxidant role of histidine and isolation of antioxidants by high-performance liquid chromatography

The radical-combining activity of Maillard reaction products [MRP_(aq)], produced by heating d-glucose and l-histidine (3:1) in a 0.1 M phosphate buffer for 10 h at 105°C (final pH 6.53), was estimated directly by means of a diphenylpicrylhydrazyl radical (DPPH^·) method. Additionally, the indirect methods of peroxide values changes (oven test), hexanal formation, and protection factors (Rancimat method) were determined on a lipid model system that consisted of sunflower seed oil/water (1:2), emulsified with 3% (w/w) Tween 40. Results from the DPPH^· method showed a potential antioxidant activity of MRP_(aq), which was confirmed by the indirect methods. Surprisingly, histidine in solution alone (heated or not) exhibited an antioxidant activity greater than or similar to the MRP_(aq) activity in the indirect methods with the lipid model system, in contrast to the results from the DPPH^· method. The suitability of various solvents for extraction of potential antioxidant compounds from freeze-dried MRP_(aq) was examined, and ethanol extracts showed the greatest activity by the DPPH^· method. Consequently, the ethanol extract of freeze-dried MRP_(aq) was separated by means of preparative reverse-phase high-performance liquid chromatography (HPLC) with a 0.05 M phosphate buffer (pH 4.4)/water/acetonitrile gradient system. The antioxidant activity of the eluate was measured through the DPPH^· method, and a fraction (Fraction A) with antiradical activity was further purified by preparative HPLC. Fraction B was collected, and its freeze-dried residue exhibited potent antiradical activity, significantly greater than that of the same level of n-propyl gallate.