Biomedical subjects

Harold Corke

Publications and source records attributed to Harold Corke.

17 recordsLinked to original sources

PubMed2006

Rapid identification of betacyanins from Amaranthus tricolor, Gomphrena globosa, and Hylocereus polyrhizus by matrix-assisted laser desorption/ionization quadrupole ion trap time-of-flight mass spectrometry (MALDI-QIT-TOF MS).

Natural betacyanins have attracted great attention as food colorants and potential antioxidants. Matrix-assisted laser desorption/ionization quadrupole ion trap time-of-flight mass spectrometry (MALDI-QIT-TOF MS) is a new and powerful technique for the identification of low molecular weight compounds. This study is the first to employ MALDI-QIT-TOF MS to rapidly identify, within a few minutes, a great number of betacyanins in crude extracts from Amaranthus tricolor seedlings, Gomphrena globosa flowers, and Hylocereus polyrhizus fruits. The fresh crude extract samples without any purification were directly used for MALDI-QIT-TOF MS analysis with 2,5-dihydroxybenzoic acid as a matrix. The MS2 and MS3 spectrometric data acquired could provide important characteristic information for structural elucidation of the betacyanins. Fourteen free and acylated betacyanins, belonging to amaranthin-type, betanin-type, and gomphrenin-type betacyanins, respectively, were identified. However, the related isomers should be differentiated with the aid of HPLC.

Amaranthaceae↗

PubMed2005

Phenolic antioxidants (hydrolyzable tannins, flavonols, and anthocyanins) identified by LC-ESI-MS and MALDI-QIT-TOF MS from Rosa chinensis flowers.

Rosa chinensis (Yuejihua) is a well-known ornamental plant, and its flowers are commonly used in traditional Chinese medicine. Methanolic crude extracts of dried R. chinensis flowers were used for simultaneous determination of phenolic constituents by liquid chromatography-mass spectrometry (LC-MS) and matrix-assisted laser desorption/ionization quadrupole ion trap time-of-flight mass spectrometry (MALDI-QIT-TOF MS). A total of 36 known and unknown phenolics were identified as hydrolyzable tannins, flavonols, and anthocyanins, mainly including gallotannins (mono-, di-, or trigalloylglucopyranosides), ellagitannins, quercetin, quercetin/kaempferol mono- and diglycosides, and cyanidin/pelargonidin diglycosides. MALDI-QIT-TOF MS was applied not only to verify most phenolics isolated and identified by LC-MS but also to tentatively identify two ellagitannins (rugosins B and C) not isolated and unidentified by LC-MS. This study is the first to demonstrate the rapid and successful use of MALDI-QIT-TOF MS and LC-MS to directly and simultaneously identify phenolics in the crude extracts of R. chinensis flowers without any purification. The antioxidant activity of the crude extracts from R. chinensis flowers was also measured with three assay methods. The results showed that the phenolic antioxidants from R. chinensis flowers exhibited very strong radical scavenging effect and antioxidant power. High levels of flavonols and hydrolyzable tannins might be important bioactive principles in the dried R. chinensis flowers.

Anthocyanins↗

PubMed2005

Biting efficiency in relation to incisal angulation.

Previous studies suggest the orientation of the incisor teeth to the path of jaw movement pronouncedly affects their efficiency of action. To test this hypothesis, upper and lower incisal portions of a study model with ideal Asian occlusion were mounted on a mechanical tester and impressed into rectangular blocks made of 15.3% w/w starch gels or Cheddar cheese. At varying angulations of attack between the long axis of the teeth (defining the orientation of the tooth crown) and force direction, the teeth were driven into the blocks for 4-6mm until fractures had grown in the foods. Both the angle of attack and the work divided by fractured area produced in the food, termed 'work to fracture', were measured. The food type (cheese or gel), incisal type (upper or lower pair) and angle of inclination were significant effects on the works to fracture. The minimal work was for angles slightly proclined to the vertical, although only angles of proclination >40 degrees were significantly higher than all other angles. Retroclination or large angles of proclination made little difference to the work done, but produced markedly off-axis cracks. It is suggested that human incisors act most efficiently at small gapes and that orthodontic corrections will thus offer definite functional benefits.

Cheese↗

PubMed2005

Structure-radical scavenging activity relationships of phenolic compounds from traditional Chinese medicinal plants.

Traditional Chinese medicinal plants associated with anticancer contain a wide variety of natural phenolic compounds with various structural features and possessing widely differing antioxidant activity. The structure-radical scavenging activity relationships of a large number of representative phenolic compounds (e.g., flavanols, flavonols, chalcones, flavones, flavanones, isoflavones, tannins, stilbenes, curcuminoids, phenolic acids, coumarins, lignans, and quinones) identified in the traditional Chinese medicinal plants were evaluated using the improved ABTS*+ and DPPH methods. Different categories of tested phenolics showed significant mean differences in radical scavenging activity. Tannins demonstrated the strongest activity, while most quinones, isoflavones, and lignans tested showed the weakest activity. This study confirmed that the number and position of hydroxyl groups and the related glycosylation and other substitutions largely determined radical scavenging activity of the tested phenolic compounds. The differences in radical scavenging activity were attributed to structural differences in hydroxylation, glycosylation and methoxylation. The ortho-dihydroxy groups were the most important structural feature of high activity for all tested phenolic compounds. Other structural features played a modified role in enhancing or reducing the activity. Within each class of phenolic compounds, the structure-activity relationship was elucidated and discussed. This study reveals the structure-activity relationships of a large series of representative natural phenolic compounds more systematically and fully than previous work. Structure-radical scavenging activity relationships of some natural phenolics identified in the medicinal plants were evaluated for the first time.

Drugs, Chinese Herbal↗

PubMed2005

Free radical scavenging properties and phenolic content of Chinese black-grained wheat.

Free radical scavenging properties and phenolic content of extracts from a novel Chinese black-grained wheat were evaluated for comparison with selected wheat controls. Extracts of bran and whole meal were compared for their scavenging activities against the 2,2-diphenyl-1-picryhydrazyl (DPPH) free radical. The total phenolic content and phenolic acid levels were determined using colorimetric and high-performance liquid chromatography (HPLC) methods, respectively. There were significant differences in radical scavenging activities and phenolic contents among bran or whole meal samples of Chinese black-grained wheat and selected wheat controls. Chinese black-grained wheat had the strongest scavenging activity and the highest total phenolic content among the wheat samples. The scavenging activity and total phenolic content of wheat bran was generally twice as high as that of whole meal. A positive correlation was found between DPPH radical scavenging activity and total phenolic content of bran (R = 0.86) and whole meal (R = 0.96). In addition, HPLC analysis detected the presence of gallic, p-hydroxybenzoic, caffeic, syringic, p-coumaric, vanillic, gentisic, o-coumaric acid, and ferulic acids in wheat bran. Ferulic acid content was highest among the phenolic acids. Chinese black-grained wheat may be considered as a potential source of natural antioxidants given its high free radical scavenging ability and phenolic content. Additional research is needed to further investigate other phenolic compounds and evaluate their contribution to the antioxidant activity in order to understand the nutraceutical value of the novel black-grained wheat genotype.

Biphenyl Compounds↗

PubMed2005

Antioxidant capacity of 26 spice extracts and characterization of their phenolic constituents.

Total equivalent antioxidant capacity (TEAC) and phenolic content of 26 common spice extracts from 12 botanical families were investigated. Qualitative and quantitative analyses of major phenolics in the spice extracts were systematically conducted by reversed-phase high-performance liquid chromatography (RP-HPLC). Many spices contained high levels of phenolics and demonstrated high antioxidant capacity. Wide variation in TEAC values (0.55-168.7 mmol/100 g) and total phenolic content (0.04-14.38 g of gallic acid equivalent/100 g) was observed. A highly positive linear relationship (R2= 0.95) obtained between TEAC values and total phenolic content showed that phenolic compounds in the tested spices contributed significantly to their antioxidant capacity. Major types of phenolic constituents identified in the spice extracts were phenolic acids, phenolic diterpenes, flavonoids, and volatile oils (e.g., aromatic compounds). Rosmarinic acid was the dominant phenolic compound in the six spices of the family Labiatae. Phenolic volatile oils were the principal active ingredients in most spices. The spices and related families with the highest antioxidant capacity were screened, e.g., clove in the Myrtaceae, cinnamon in the Lauraceae, oregano in the Labiatae, etc., representing potential sources of potent natural antioxidants for commercial exploitation. This study provides direct comparative data on antioxidant capacity and total and individual phenolics contents of the 26 spice extracts.

Antioxidants↗

PubMed2005

Anthocyanins, flavonols, and free radical scavenging activity of Chinese bayberry (Myrica rubra) extracts and their color properties and stability.

Characterization of anthocyanins and flavonols and radical scavenging activity assays of extracts from four Chinese bayberry (Myrica rubra) varieties with different fruit colors were carried out. One dominant anthocyanin and three major flavonols were isolated by HPLC, and cyanidin-3-O-glucoside and two of three flavonols, myricetin and quercetin-3-O-rutinoside, were identified by cochromatography with authentic standards. Both DPPH* and ABTS*(+) cation assays indicated that the black varieties (Biji and Hunan) demonstrated much higher radical scavenging activities than the pink (Fenhong) and yellow (Shuijing) varieties, which may be attributed to much higher levels of anthocyanins, flavonoids, and total phenolics in the black varieties. Biji and Hunan had 6.49 and 6.52 mM Trolox equivalent antioxidant capacity (TEAC) per 100 g of fresh weight, whereas the pink (Fenhong) and yellow (Shuijing) bayberries had 1.32 and 1.31 mM TEAC/100 g. Different fruit color was reflected by the surface color and pigment extract color. Color stability of the pigment was dependent on pH, and the pigment was more stable at low pH (pH approximately 1.5). The lightness (L) increased while the chroma (C value) decreased with increase of pH until pH 5, but higher pH caused a small decrease for L and an increase for C.

Anthocyanins↗

PubMed2005

HPLC characterization of betalains from plants in the amaranthaceae.

HPLC characterization of reversed-phase (RP) high-performance liquid chromatography (HPLC) has been widely used in separation and identification of plant pigments. An effective RP-HPLC-based method is established to systematically isolate, identify, and quantitate the betalain pigments in the plants of 37 species of eight genera in the Amaranthaceae. A total of 16 betacyanins and three betaxanthins are characterized mainly using the RP-HPLC method and also with the aid of mass spectroscopy. The identified betacyanins include eight amaranthine-types, six gomphrenin-types, and two betanin-types. They are also divided into six simple (nonacylated) betacyanins and 10 acylated betacyanins. Acylated betacyanins are identified as betanidin 5-O-beta-glucuronosylglucoside or betanidin 6-O-beta-glucoside acylated with ferulic, p-coumaric, or 3-hydroxy-3-methylglutaric acids. Three betaxanthins were separated from Celosia species in the Amaranthaceae and identified to be immonium conjugates of betalamic acid with dopamine, 3-methoxytyramine, and (S)-tryptophan; the latter two are found to be new betaxanthins from plants.

Amaranthaceae↗

PubMed2004

Antioxidant phenolic constituents in roots of Rheum officinale and Rubia cordifolia: structure-radical scavenging activity relationships.

The phenolic constituents in the roots of Rheum officinale and Rubia cordifolia were identified with the aid of high-performance liquid chromatography and liquid chromatography-mass spectrometry and by comparison with authentic standards. A total of 17 hydroxyanthraquinones, gallic acid, and tannins were separated, and 14 of them were identified, being the main phenolic constituents present. Their antioxidant activity (Trolox equivalent antioxidant capacity) was evaluated using the improved 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt method. Hydroxyanthraquinones were the predominant antioxidant phenolic constituents in the roots of R. cordifolia, and tannins and gallic acid were the predominant antioxidant phenolic constituents in the roots of R. officinale. The structure-radical scavenging activity relationships of the tested hydroxyanthraquinones were systematically demonstrated as follows: Hydroxy groups on one benzene ring of the anthraquinone structure were essential for hydroxyanthraquinones to show activity, the ortho-dihydroxy structure in the hydroxyanthraquinone molecules could greatly enhance their radical scavenging effect, and glycosylation of the hydroxyanthraquinones reduced activity.

Anthraquinones↗

PubMed2004

Hypoglycemic and hypolipidemic effects and antioxidant activity of fruit extracts from Lycium barbarum.

The hypoglycemic and hypolipidemic effects of Lycium barbarum fruit water decoction, crude polysaccharide extracts (crude LBP), and purified polysaccharide fractions (LBP-X) in alloxan-induced diabetic or hyperlipidemic rabbits were investigated through designed sequential trials and by measuring blood glucose and serum lipid parameters. Total antioxidant capacity was also assessed using trolox equivalent antioxidant capacity (TEAC) and oxygen radical absorbance capacity (ORAC) assay. It was found that the three Lycium barbarum fruit extracts/fractions could significantly reduce blood glucose levels and serum total cholesterol (TC) and triglyceride (TG) concentrations and at same time markedly increase high density lipoprotein cholesterol (HDL-c) levels after 10 days treatment in tested rabbits, indicating that there were substantial hypoglycemic and hypolipidemic effects. Hypoglycemic effect of LBP-X was more significant than those of water decoction and crude LBP, but its hypolipidemic effect seemed to be weaker. Total antioxidant capacity assay showed that all three Lycium barbarum extracts/fractions possessed antioxidant activity. However, water and methanolc fruit extracts and crude polysaccharide extracts exhibited stronger antioxidant activity than purified polysaccharide fractions because crude extracts were identified to be rich in antioxidants (e.g., carotenoids, riboflavin, ascorbic acid, thiamine, nicotinic acid). Lycium barbarum polysaccharides (glycocojugates), containing several monosaccharides and 17 amino acids, were major bioactive constituents of hypoglycemic effect. Both polysaccharides and vitamin antioxidants from Lycium barbarum fruits were possible active principles of hypolipidemic effect.

Animals↗

PubMed2004

Antioxidant activity and phenolic compounds of 112 traditional Chinese medicinal plants associated with anticancer.

Cancer prevention and treatment using traditional Chinese medicines have attracted increasing interest. This study characterizes antioxidant activity and phenolic compounds of traditional Chinese medicinal plants associated with anticancer, comprising 112 species from 50 plant families. The improved ABTS(*+) method was used to systematically assess the total antioxidant capacity (Trolox equivalent antioxidant capacity, TEAC) of the medicinal extracts. The TEAC values and total phenolic content for methanolic extracts of herbs ranged from 46.7 to 17,323 micromol Trolox equivalent/100 g dry weight (DW), and from 0.22 to 50.3 g of gallic acid equivalent/100 g DW, respectively. A positive, significant linear relationship between antioxidant activity and total phenolic content (all R(2) values>/=0.95) showed that phenolic compounds were the dominant antioxidant components in the tested medicinal herbs. Major types of phenolic compounds from most of the tested herbs were preliminarily identified and analyzed, and mainly included phenolic acids, flavonoids, tannins, coumarins, lignans, quinones, stilbenes, and curcuminoids. These medicinal herbs exhibited far stronger antioxidant activity and contained significantly higher levels of phenolics than common vegetables and fruits. Traditional Chinese medicinal plants associated with anticancer might be potential sources of potent natural antioxidants and beneficial chemopreventive agents.

Antineoplastic Agents, Phytogenic↗

PubMed2003

Supercritical carbon dioxide extraction of oil and squalene from amaranthus grain.

Supercritical carbon dioxide (SC CO(2)) was used for the extraction of oil and squalene from Amaranthus grain. Very small amounts of oil could be extracted by SC CO(2) from undisrupted grains, although SC CO(2) possesses higher diffusivity. Grinding increased the extraction rate and oil yield, and smaller particle size gave higher extraction rate. The oil yield and initial extraction rate increased linearly with the increasing SC CO(2) flow rate from 1 to 2 L/min. Increasing the flow rate of SC CO(2) above 2 L/min resulted in only a slight increase of oil yield and extraction rate. In the pressure range of 150-250 bar, extraction decreased with increasing temperature at a constant pressure, whereas at a pressure of 300 bar, the extraction yield increased with increasing temperature. Possible reasons for this are discussed. Effects of temperature and pressure on squalene yield were different from those on oil yield. A good oil yield (4.77 g of oil/100 g of grain) was obtained at 40 degrees C and 250 bar. The highest squalene yield (0.31 g of squalene/100 g of grain) and concentration (15.3% in extract) were obtained at 50 degrees C and 200 bar, although the oil yield under this condition was low (2.07 g of oil/100 g of grain). The moisture content within 0-10% had little influence on yields of oil and squalene at 40 degrees C and 250 bar. Finally, the oil yield and the squalene concentration in the extracts by SC CO(2) were compared to those by solvent extraction.

Amaranthus↗

PubMed2003

Oil and squalene in amaranthus grain and leaf.

Amaranthus grain of 104 genotypes from 30 species was investigated for oil and squalene contents and fatty acid profiles. The overall average oil content in Amaranthus grain was 5.0%, ranging from 1.9 to 8.7%. Squalene concentration in extracted oils ranged from trace to 7.3%, with an average concentration of 4.2%. The average contents of three major fatty acids in Amaranthus grain were 22.2, 29.1, and 44.6% for palmitic, oleic, and linoleic, respectively. The average fat content in dried mature leaves of 45 Amaranthus genotypes was 1.63%, ranging from 1.08 to 2.18%. The squalene concentration in leaf lipid extracts averaged 0.26%, ranging from trace to 0.77%, which is much lower than that from seeds. The major fatty acids of leaf extracts were linolenic, linoleic, and palmitic. Linolenic ranged from 56.5 to 62.0% of total fatty acids; linoleic, from 15.5 to 24.7%; and palmitic acid, from 13.5 to 15.5%. As for the fatty acid compositions at different growth stages, fatty acid content in leaf lipid was lower in mature leaves than in young leaves. The saturated/unsaturated ratio decreased when the leaf grew to maturity. Principal component analysis (PCA) was carried out on compositional characteristics of grain. The first two components accounted for 70% of the total variance (38.3 and 21.7%, respectively). There was a positive correlation between oil content and squalene yield, and a negative correlations were found between linoleic and either of the other two major fatty acids, palmitic and oleic. The taxonomic relationship among the species was also elucidated by PCA.

Amaranthus↗

PubMed2003

Physical properties of octenyl succinic anhydride modified rice, wheat, and potato starches.

The physical properties of octenyl succinic anhydride (OSA) starches prepared from rice, wheat, and potato starches were studied. Rice and wheat OSA starches had significantly higher peak viscosity (PV), hot paste viscosity (HPV), and cool paste viscosity (CPV), but potato OSA starch had only significantly higher CPV, relative to the native starch. The gel hardness was higher with lower degree of substitution (DS) but lower with higher DS OSA compared to native starch. The swelling volumes (SV) of rice and wheat OSA starches were significantly higher compared to native starch, but the SV of potato OSA starch was slightly lower at high DS. The gelatinization temperature (GT) of rice OSA starches was sharply lower at low DS; for wheat OSA starch it was slightly lower even at high DS, but potato OSA starches had higher GT than the native starch. The enthalpy of all the OSA starches decreased gradually with increased DS. This study showed that the magnitude of changes in physical properties of OSA-modified starches depends not only on their DS but also on the botanical origin of the native starches.

Chemical Phenomena↗

PubMed2003

Antioxidant activity of betalains from plants of the amaranthaceae.

Antioxidant activity of betalain pigments (seven pure compounds and four combined fractions) from plants of the family Amaranthaceae was evaluated using the modified DPPH(*) (1,1-diphenyl-2-picrylhydrazyl) method. All tested betalains exhibited strong antioxidant activity. Their EC(50) values ranged from 3.4 to 8.4 microM. Gomphrenin type betacyanins (mean = 3.7 microM) and betaxanthins (mean = 4.2 microM) demonstrated the strongest antioxidant activity, 3-4-fold stronger than ascorbic acid (13.9 microM) and also stronger than rutin (6.1 microM) and catechin (7.2 microM). Antioxidant activity of the tested betalains decreased in the following order: simple gomphrenins > acylated gomphrenins > dopamine-betaxanthin > (S)-tryptophan-betaxanthin > 3-methoxytyramine-betaxanthin > betanin/isobetanin > celosianins > iresinins > amaranthine/isoamaranthine. This study also investigated and discussed the relationship between the chemical structure and the activity of the betalains. The free radical scavenging activity of the betalains usually increased with the numbers of hydroxyl/imino groups and, moreover, depended on the position of hydroxyl groups and glycosylation of aglycones in the betalain molecules.

Amaranthaceae↗

PubMed2002

Pasting properties of gamma-irradiated rice starches as affected by pH.

Changes in the viscosity properties of gamma-irradiated rice starches (from 1 to 25% amylose content) from four genotypes (JY293, Jiayu 293; XS, Xiushui; ZF504, Zhefu 504; and ZXN, Zaoxiannuo) during pasting in water (pH 7) or in different pH solutions were studied using a rapid visco analyzer. Peak viscosity (PV) of all native rice starches was little affected at pH 4 and 10, while hot paste viscosity (HPV) and cool paste (final) viscosity (CPV) were generally lower at pH 4 and higher at pH 10 as compared with that at pH 7. The PV, HPV, and CPV of gamma-irradiated starches were higher at pH 4 and lower at pH 10 than pH 7. All viscosity characteristics of native rice starches were reduced in stronger alkali (pH 11.5) or acidic (pH 2.5) solutions. However, the gamma-irradiated starches were substantially higher at pH 2.5 but lower at pH 11.5, indicating that the effect of irradiation was highly pH dependent. The swelling volume of irradiated ZF504 and JY293 starch at all irradiation levels was higher at pH 4 than pH 7, while the values were lowest at pH 2.5. The irradiated ZXN and XS starches had higher swelling volumes at pH 4 and pH 2.5 than pH 7. Differential scanning calorimetry analysis showed that gamma-irradiation caused progressively lower gelatinization peak temperature (T(p)) and higher gelatinization range (T(r)) at pH 7. T(p) was higher and T(r) was lower at a much stronger acidic condition (pH 1) for both native and irradiated starches. The possibility of using viscosity changes in low pH for the detection of irradiated starch was discussed.

Gamma Rays↗

PubMed2002

Extraction and purification of squalene from amaranthus grain.

Grain amaranth has been suggested as an alternative to marine animals as a natural source of squalene. Oil contents, squalene contents, and fatty acid profiles were determined in 11 genotypes of four grain amaranth species. Although the oil contents of grain amaranth were low (from 5.1% in Amaranthus tricolor to 7.7% in Amaranthus cruentus) as compared to other oil-containing grains, high concentrations of squalene were found in total lipids, ranging from 3.6% in Amaranthus hypochondriacus to 6.1% in A. tricolor. The major fatty acids in Amaranthus oil consisted of palmitic acid (19.1-23.4%), oleic acid (18.7-38.9%), and linoleic acid (36.7-55.9%). A high degree of unsaturation was observed in Amaranthus oils, with S/U ratios of 0.26-0.32. A method to isolate and purify the squalene from Amaranthus oil was developed. After the saponification of K112, the squalene content increased from 4.2% in the crude oil to 43.3% in the unsaponifiables by the removal of the saponifiables. The unsaponifiables were fractionated by silica gel column chromatography to get highly purified squalene. The squalene purity in certain fractions was as high as 98%. Combining the fractions rich in squalene gave a 94% squalene concentrate, with a yield of 90%. The structure of squalene in the purified sample was confirmed by comparison of its ultraviolet spectrum with a standard and from its nuclear magnetic resonance spectra.

Amaranthus↗