Antioxidant activity of almonds and their by-products in food model systems

Antioxidant activities of almond whole seed, brown skin, and green shell cover extracts, at 100 and 200 ppm quercetin equivalents, were evaluated using a cooked comminuted pork model, a β-carotene-linoleate model, and a bulk stripped corn oil system. Retention of β-carotene in a β-carotene-linoleate model system by almond whole seed, brown skin, and green shell cover extracts was 84–96, 74–83, and 71–93%, respectively. In a bulk stripped corn oil system, green shell cover extract performed better than brown skin and whole seed extracts in inhibiting the formation of both primary and secondary oxidation products. In a cooked comminuted pork model system, green shell cover and brown skin extracts inhibited the formation of TBARS, total volatiles, and hexanal more effectively than did the whole seed extract. HPLC analysis revealed the presence of caffeic, ferulic, p-coumaric, and sinapic acids as the major phenolic acids in all three almond extracts examined.     

Extraction and identification of antioxidants from the spice Aframomum danielli

Successive extractions with diethyl ether and methanol of the whole seeds of the spice Aframomum danielli yielded diethyl ether extract (ADEE), 13.9%, and methanol extract (ADM), 3.4%, respectively. Similarly, reextraction of the defatted seeds of A. danielli successively with diethyl ether and methanol yielded extracts DFADEE (7.9%) and DFADM (6.7%), respectively. When these extracts were added to refined peanut oil (PNO) at 200 ppm, they showed good antioxidative effects. The percentage antioxidant effectiveness (AE) values were as follows: DFADM (87.3) > ADM (85.3) > ADEE (83.4)=tert-butyl hydroquinone (83.4) on day 20 of storage in an oven maintained at 65±1°C. Generally, antioxidant extracts prepared from A. danielli were also more effective than butylated hydroxytoluene and α-tocopherol in stabilizing refined PNO. Antioxidant components of A. danielli were tentatively identified as phenolic compounds of the trihydroxy type with reducing properties. All extracts prepared from A. danielli showed strong ultraviolet-absorbing characteristics, and methanol was a good extracting solvent.     

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).     

Antioxidant activity of mediterranean plant leaves: Occurrence and antioxidative importance of α-tocopherol

α-Tocopherol was identified as the main antioxidant in hexane extracts of leaves of sixteen Mediterranean plant species. The α-tocopherol content was determined by a two-step procedure involving column and gas chromatography with α-tocopherol acetate as internal standard. The tocopherol content of the extracts was in the range of 0.0–4.7%, and that of the dry leaves was 0–846 ppm. The highest α-tocopherol content was found in the leaves of a Mediterranean oak,Quercus ilex. The antioxidative activity, which was previously investigated, was correlated with the α-tocopherol content. Correlation coefficients were 0.947 and 0.904 for extracts and leaves, respectively.     

Purification of Extracted Fatty Acids from the Microalgae <Emphasis Type="Italic">Spirulina</Emphasis>

The fatty acid (FA) analysis of microalgae Spirulina was studied by applying accelerated solvent extraction (ASE) and followed by purification using solid-phase extraction (SPE). The objective was to develop a sensitive and reliable purification procedure to remove pigment in lipids co-extracted from Spirulina. Four extraction solvents were used for the ASE lipids extraction. The extraction efficiency was ranked in the following order: chloroform:methanol > dichloromethane:methanol > ethanol > hexane. The major composition of fatty acids were examined. Hexane and chloroform:methanol were compared for the purification step. The amounts of sorbent (Silica gel H), sample, and the volume of eluent were optimized during SPE procedure. This purification step can successfully remove the pigments from extracted lipids. For 0.1 g algae sample, chloroform:methanol (2:1, v/v) was the optimal extraction solvent, 0.3 g silica gel was the optimal amount of sorbent, with 7 mL for the volume of eluent. For hexane as the extraction solvent, 0.5 g algae sample, 0.3 g silica gel was the optimal amount of sorbent, 5 mL was the optimal volume of eluent. The calibration curve was produced comprised from five samples that contained FAME concentrations which was ranged from 0.1 to 10 mg/L (R ² > 0.99). The recoveries of fatty acids were 67.97–134.37%, 74.20–99.13% and 98.34–115.42%, with standard deviations (SD) of three replicate detections ranged from 1.09 to 8.41%.     

Antioxidant activity of burdock (Arctium lappa Linné): Its scavenging effect on free-radical and active oxygen

The antioxidant activity and free-radical and active oxygen-scavenging activity of burdock extracts were investigated. Of the solvents used for extraction, water yielded the greatest amount of extract that exhibited the strongest antioxidant activity. Water extracts of burdock (WEB) and hot water extracts of burdock (HWEB) exhibited comparable and marked activity on inhibition of linoleic acid peroxidation, indicating that heat treatment did not alter the antioxidant activity of WEB. WEB and HWEB produced significantly lower (P<0.05) malondialdehyde (MDA) in both linoleic acid and liposome model systems than did the control. Moreover, mixtures of tocopherol (Toc), WEB, and HWEB exhibited a remarkable synergistic antioxidant effect in a liposome system; WEB and HWEB thus potentiated the action of Toc. Furthermore, WEB and HWEB displayed a marked inhibitory effect on lipid peroxidation of rat liver homogenate in vitro. WEB and HWEB exhibited an 80% scavenging effect on α,α-diphenyl-β-picrylhydrazyl radical and marked reducing power, indicating that WEB and HWEB act as primary antioxidants. Both extracts at a dose of 1.0 mg exhibited a 60.4–65.0% scavenging effect on superoxide and an 80.5% scavenging effect on hydrogen peroxide. They also showed a marked scavenging effect on the hydroxyl radical. These results revealed that WEB and HWEB are also active as oxygen scavengers and as secondary antioxidants. Based on these results, termination of free-radical reactions and quenching of reactive oxygen species in burdock extracts are suggested to be, in part, responsible for the antioxidant activity of burdock extracts.     

The Interactions Between Rapeseed Lipoxygenase and Native Polyphenolic Compounds in a Model System

The focus of the present research was to study inhibition of lipoxygenase activity by rapeseed native polyphenols and the interactions between those compounds and the enzyme. The enzyme and polyphenolic compounds (polyphenols, phenolic acids) were extracted from rapeseed (Brassica napus) varieties Aviso and PR45DO3. The total phenolic compounds concentration in tested rapeseed was 1,485–1,691 mg/100 g d.m. (dry matter) and the free phenolic acids content in both rapeseed varieties was about 76 μg/100 g d.m. The isolated proteins showed lipoxygenase activity. Prooxidant properties of phenolic compounds in the presence of lipoxygenase and linoleic acid were observed rather in the case of extracts containing a relatively high concentration of miscellaneous polyphenols. Antioxidant properties were recorded in the case of phenolic acid extracts which contain only 1.4–1.9% of phenolics present in raw phenolic extracts. We propose that the prooxidant effect of phenolic compounds comes from quinone and oxidized polyphenols formation. The observed antioxidant activity of phenolic acid extracts is probably due to their ability to scavenge free radicals formed from linoleic acid. However, reduction of lipoxygenase ferric to ferrous ions, which prevent the activation of the enzyme and inhibited its activity, was also observed.     

Antiradical activity of extracts of almond and its by-products

Antioxidant activities of ethanolic extracts of whole almond seed, brown skin, and green shell cover were evaluated using different free radical trapping assays. Trolox equivalent antioxidant capacity assay revealed that the total antioxidant capacities of brown skin and green shell cover extracts were 13 and 10 times greater than that of the whole seed extract at the same extract concentration. The free radical-scavenging activity of extracts of brown skin and green shell cover also exceeded that of the whole seed. The scavenging activity of superoxide radical by different almond extracts ranged from 76 to 97% at 100 ppm and 85 to 99% at 200 ppm. The corresponding reduction of hydrogen peroxide concentration was 59–66% (100 ppm) and 86–91% (200 ppm). The hydroxyl radical-scavenging capacities at 100 and 200 ppm were 16 and 42% for whole seed, 57 and 100% for brown skin, and 40 and 56% for green shell extracts, respectively. A 100% scavenging activity of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical was observed for brown skin and green shell extracts at 100 and 200 ppm concentrations, respectively, and whole seed extracts scavenged 21 (at 100 ppm) and 73% (at 200 ppm) of the DPPH radical.     

Nitrogen Fertilization Effects on Quality of Organic Matter in a Grassland Soil

Organic matter is important to sustain and improve soil quality and productivity. A field experiment determined the effects of 27 annual spring surface-broadcast applications of ammonium nitrate at 0, 112 and 224 kg N ha⁻¹ year⁻¹ to bromegrass (Bromus inermis Leyss) on light fraction organic matter (LFOM), total amino acids, amino acid C (AAC) and N (AAN), ammonium–N (NH₄–N) and, total organic matter (TOM) in a thin Black Chernozemic loam soil at Crossfield, Alberta, Canada. The concentration and mass of LFOM, AAC and AAN in the 0–5, 5–10 and 10–15 cm soil layers increased with N rate, with greatest increase in the 0–5 cm layer. The response to N application was much greater for LFOM than for TOM. The changes in soil LFOM, AAC, AAN, NH₄–N and TOM suggest that N application increases the quantity of light fractions and improves the quality of total organic matter in the soil.     

Chemotactic tube-foot responses of a spongivorous sea starPerknaster fuscus to organic extracts from antarctic sponges

Hexane, chloroform, and methanol extracts of 18 species of antarctic sponges were tested for their ability to induce sustained tube-foot retraction in the antarctic spongivorous sea starPerknaster fuscus. Extracts were imbedded in silicone and used to coat the tip of a glass rod, which was allowed to contact an extended tube-foot. Retraction times were measured and compared with three controls: contact with a glass rod coated with a hexane extract of fish (feeding stimulant), contact with the glass rod alone (mechanical control), and contact with the glass rod coated with silicone alone (silicone control). Only extracts of the spongeMycale acerata did not elicit significantly longer tube-foot retraction times than controls for at least one of the three organic extracts. Hexane sponge extracts elicited the lowest levels of significant tube-foot responses, with only 39% of the sponge species tested showing activity in this fraction. In contrast, chloroform and methanol extracts elicited a significant tube-foot retraction response in 73% and 78% of the species tested, respectively. This indicates that in this assay repellent metabolites are generally more polar substances. It remains to be determined that secondary metabolites are responsible for all of the tube-foot retraction responses detected in sea stars exposed to sponge extracts; bioactive secondary metabolites have been isolated from a number of these antarctic sponges. It may be of ecological significance that the two rapidly growing sponges,Homaxinella balfourensis andMycale acerata, were either not repellent or had low repellency, and thatM. acerata is the primary dietary item ofPerknaster fuscus.     

Sterols,methyl sterols,triterpene alcohols and fatty acids of the kernel fat of different malagasy mango(Mangifera indica) varieties

The kernel fat content of 16 different mango varieties collected from the Northwestern part of Madagascar island were examined. The fat content (22–54%) was determined by chloroform/methanol extraction. Investigation by gas liquid chromatography (GLC) revealed 15 fatty acids, mainly palmitic (7–12%), stearic (22–40%), oleic (41–48%) and linoleic (7–17%). Significant correlations were observed among the main fatty acids. Testing for the sterol fraction in 15 mango varieties allowed us to separate and quantitatively analyze 7 sterols by GLC. The main sterols wereβ-sitosterol (47–76%), stigmasterol (12–23%) and campesterol (7–12%). The stigmasterol/campesterol ratio (1.2:2.3) was lower in mango kernel fat than in cocoa butter. Among the 4-methyl sterol fractions, gramisterol, lophenol, obtusifoliol and citrostadienol were tentatively identified by GLC. Lupeol, cycloartenol,α- andβ-amyrins and friedelinol were tentatively identified by GLC in the triterpene alcohols fractions.     

Generation of phospholipid artefacts during extraction of developing soybean seeds with methanolic solvents

The major phospholipids of soybean cotyledons during development were phosphatidylcholine (45–55%), phosphatidylethanolamine (24–28%), and phosphatidylinositol (15–18%) when the tissue was steam-killed prior to extraction of the lipids. The only other phospholipids of any significance (4–6%) was identified as phosphatidylglycerol. Phosphatidic acid was a minor constituent (<1%), and neither N-acyl phosphatidylethanolamine norbis-phosphatidic acid were detected in appreciable (>0.1% of the total lipid phosphorus) quantities. When fresh cotyledons were rapidly homogenized in mixtures of chloroform and methanol or in methanol alone, phosphatidylmethanol was formed in variable amounts (0–20% of the total phospholipid), and when cotyledons were soaked in methanol prior to homogenizing, phosphatidylmethanol became the major phospholipid, accounting for up to 75% of the total lipid phosphorus. Phosphatidylmethanol was formed by the phospholipase D-catalyzed transphosphatidylation of phosphatidylcholine and phosphatidylethanolamine during extraction.     

Fatty Acid Composition of Turkish <Emphasis Type="Italic">Rhododendron</Emphasis> Species

This study describes work aimed at the rapid evaluation of the fatty acid (FA) composition of Turkish Rhododendron species, particularly the leaves and the flowers of the toxic plants, R. ponticum and R. luteum. The FA profiles of the available parts of three other nonpoisonous Rhododendron species were also investigated. Subtotal extracts obtained (using n-hexane, chloroform and methanol) from total chloroform:methanol (1:1) extracts were analyzed and compared to each other. Palmitic acid was found to be the most abundant FA in almost all Rhododendron extracts, and the majority of leaf and flower extracts contained significant portions of C18 unsaturated FAs (18:1n-9, 18:2n-6, 18:3n-3). The n-hexane extracts of R. ponticum leaves and R. luteum flowers were unique, as they contained an unusual series of even-chain iso FAs (C16–C24). Especially the n-hexane extracts were found to comprise uncommon FAs with odd-numbered carbons (C13–C29). Overall, n-hexane proved to be the best solvent by representing the richest FA profile, whereas chloroform or methanol appeared less suitable for FA analyses. Appreciable intra-species variations in FA compositions among the leaves as well as other anatomical parts examined were observed. This study highlights the chemotaxonomical importance of the FAs for the genus Rhododendron.     

Preparation of schiff base adducts of phosphatidylcholine core aldehydes and aminophospholipids, amino acids, and myoglobin

We have prepared Schiff base adducts of the core aldehydes of phosphatidylcholine and aminophospholipids, free amino acids, and myoglobin. The Schiff bases of the ethanolamine and serine glycerophospholipids were obtained by reacting sn-1-palmitoyl(stearoyl)-2-[9-oxo]nonanoyl-glycerophosphocholine (PC-Ald) with a twofold excess of the aminophospholipid in chloroform/methanol 2∶1 (vol/vol) for 18 h at room temperature. The Schiff bases of the amino acids and myoglobin were obtained by reacting the aldehyde with an excess of isoleucine, valine, lysine, methyl ester lysine and myoglobin in aqueous methanol for 18 h at room temperature. Prior to isolation, the Schiff bases were reduced with sodium cyanoborohydride in methanol for 30 min at 4°C. The reaction products were characterized by normal-phase high-performance liquid chromatography and on-line mass spectrometry with electrospray ionization. The amino acids and aminophospholipids yielded single adducts. A double adduct was obtained for myoglobin, which theoretically could have accepted up to 23 PC-Ald groups. The yields of the products ranged from 12 to 44% for the aminophospholipids and from 15–57% for the amino acids, while the Schiff base of the myoglobin was estimated at 5% level. The new compounds are used as reference standards for the detection of high molecular weight Schiff bases in lipid extracts of natural products. Based on presentation at the AOCS Annual Meeting & Expo in Indianapolis, Indiana, April 28–May 1, 1996.     

Effect of extraction methods on lipid yield and fatty acid composition of lipid classes containing γ-linolenic acid extracted from fungi

The effect of extraction procedures on the lipid yield and fatty acid composition of total lipid and main lipid structures (phospholipids, diacylglycerols, triacylglycerols, free fatty acids, and sterol esters) of fungal biomass (Mucor mucedo CCF-1384) containing γ-linolenic acid (GLA) was investigated. Seventeen extraction methods, divided into three groups, were tested: six with chloroform/methanol, five with hexane/alcohols, and six with common solvents or mixtures. The chloroform/methanol procedure (2∶1) was selected as standard, where lipid yield (TL/DCW, total lipid per dry cell weight) was 17.8%, considered to be 100% of lipids present. All chloroform/methanol extractions yielded more than 83% recorvey of lipids. Use of hexane/isopropanol solvent systems led to a maximum of 75% recovery. The best lipid yield was achieved by a two-step extraction with ethanol and hexane (120%). Extraction efficiency of the other solvent systems reached a maximum of 73%. Triacylglycerols were the main structures of lipid isolated; only methanol-extracted lipid contained 58.5% phospholipids. The fatty acid content of total recovered lipid was variable and depended on both the lipid class composition and the solvent system. GLA concentrations in total lipids isolated by hexane/alcohol procedures (7.3–10.7%) are comparable with classical chloroform/methanol systems (6.5–10.0%). The maximal GLA yield was obtained with chloroform/methanol/n-butanol/water/0.1 M ethylenediaminetetraacetic acid (EDTA) (2∶1∶1∶1∶0.1, by vol) and after two-step extraction with ethanol and hexane (14.3 and 13.7 g GLA/kg DCW, respectively). The highest GLA content was analyzed in the phospholipid fraction (16.1%) after using chloroform/methanol/n-butanol/water/0.1 M EDTA (2∶1∶1∶1∶0.1, by vol). Remarkably low concentrations of polyunsaturated fatty acids were determined in the free fatty acid fraction.     

Effect of meliaceous seed extracts on growth and survival ofSpodoptera frugiperda (J.E. Smith)

Hexane and ethanol extracts of seeds from 10 plant species (including neem—Azadirachta indica A. Juss.) of the family Meliaceae were incorporated into artificial diet at various doses and fed to fall armyworm [Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)] larvae in nochoice tests. All produced significant mortality, reduced larval growth rate, increased time to pupation, or all three, at some concentration. The two highest doses of all of the ethanol extracts caused 100% mortality before pupation, but the hexane extracts tended to be less effective.Aglaia cordata Hiern. ethanol extract was as potent as the comparable neem seed extract at virtually all levels, and its hexane extract was active at much lower concentrations than the neem extract was. The sublethal effects (slower growth and increased time to pupation) were usually detectable at lower doses of extract than mortality was.Mention of firm or product names does not imply recommendation or endorsement by USDA over others not mentioned.     

Quantitation by radioimmunoassay of PAF in human saliva

Approximately 75% of the PAF present in saliva is recovered on extraction of whole saliva (0.8 vol) with chloroform/methanol/water (2∶2∶1 v/v/v). PAF levels, determined by our recently developed radioimmunoassay, in saliva extracts ranged from 0.5–21 ng/mL with 59% between 2–6 ng/mL. These figures, for apparently healthy subjects, are higher than previously reported levels obtained by platelet assays. The validity of our radioimmunoassay results was checked by isolating and quantitating the PAF fraction from whole saliva. In addition, when we examined our saliva samples by platelet aggregation, low levels of PAF, comparable with the values found in the literature, were detected. Investigations revealed the presence of a substance(s) which inhibited PAF-induced platelet aggregation but which did not affect the radioimmunoassay.     

Extraction and identification of antioxidants in oats

Eight separate solvent systems were used with groats and hulls of several lines of oats to determine which system resulted in the most effective, rapid extraction of antioxidants. Antioxidant activity at room temperature was estimated by using thin-layer chromatography (TLC) along with a β-carotene spray. The greatest antioxidant activities were obtained with methanolic antioxidant extracts derived from Noble and Ogle oats and hulls. These extracts were added to soybean oil (SBO) and their effectiveness was compared with that of butylated hydroxytoluene (BHT), tertiary butyl hydroquinone (TBHQ) and a control (no additives) at 32°C, 60°C and 180°C. A petroleum ether extract of Noble oats also was tested in SBO at 180°C. Peroxide values (PV) for oils with added antioxidants during storage at 32°C and 60°C showed that the Ogle oat extract was more effective than the other oat and hull extracts or the control. There were no significant differences in effectiveness among the extracts and the control at 60°C. At 180°C, the stability of each oil was determined by measuring conjugated dienoic acid values (CD) and the relative amounts of the unoxidized fatty acid methyl esters (FAME) 18:2, 18:3 and 18:2/16:0. All oils with added oat and hull extracts had significantly lower CD and significantly higher 18:2/16:0 than oils with added BHT, TBHQ or the control during 14 days at frying temperature. Phenolic and hydroxy-phenolic antioxidant compounds with acids, alcohols, sugars or glycerides attached were tentatively identified in the oat and hull extracts by using TLC and Chromatographic sprays. To whom correspondence should be addressed at Food Science and Human Nutrition Dept., 3367 Dairy Industry Building, Iowa State University, Ames, IA 50011.     

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.     

Seasonal variation in volatile secondary compounds ofChrysothamnus nauseosus (Pallas) britt.; asteraceae ssp.hololeucus (Gray) hall. & clem. Influences herbivory

Chrysothamnus nauseosus (rubber rabbitbrush) is used by browsing animals, especially mule deer (Odocoileus hemionus), as a forage in the winter months. It is used only slightly, if at all in the summer. This dietary difference may result from changes in the secondary chemical composition of the leaves. Solvent extracts from summer and winter rabbitbrush leaves were analyzed by gas chromatography and mass spectrometry, and the volatile compounds were quantified and identified. Hexane and chloroform extracts from winter leaves exhibit a marked concentration decrease in most chemicals when compared to summer extracts. The methanol extracts revealed the presence of several chemicals in the summer leaves that were absent in winter leaves. Rubber rabbitbrush has fewer secondary volatile chemicals in the winter than in the summer. These chemical differences may influence the seasonal dietary difference observed in mule deer and other browsing animals.