不同种质鱼腥草总酚、黄酮含量及其抗氧化活性

目的：提取并测定16份鱼腥草材料(含1份峨眉蕺菜)叶片总酚和黄酮含量,研究其体外抗氧化活性。方法：以95%乙醇超声提取并测定16份综合农艺性状较好的鱼腥草材料以显色及紫外分光光度测定成分含量,DPPH、ABTS法测定抗氧化活性。结果：16份鱼腥草总酚含量变异范围为7.01～15.0mg/g;黄酮含量变异范围为3.56～11.0mg/g;DPPH法抗氧化值最小为84.7μmol/g,最大为248μmol/g;而ABTS法抗氧化能力的变幅为 78.4～218μmol/g。以总酚和黄酮含量、DPPH法以及ABTS法抗氧化能力进行聚类分析,按欧氏距离大于70可将16份鱼腥草材料分为两类。其中Ⅰ类包含11份鱼腥草材料(含峨眉蕺菜),其总酚和黄酮含量低,抗氧化能力弱。Ⅱ类包含5份鱼腥草材料,其总酚和黄酮含量高,体外抗氧化能力强。总酚、黄酮含量和体外抗氧化活性指标间相关性均达极显著水平。结论：16份鱼腥草材料总酚、黄酮含量和抗氧化活性的不同,主要是由于遗传背景所致;且总酚和黄酮含量高,体外抗氧化能力强的材料多为染色体数目大于80者。     

Phenolic Composition and Antioxidant Activities of 11 Celery Cultivars

ABSTRACT:  Eleven cultivars of celery, belonging to 2 species, were collected and analyzed for their phenolic compound composition and antioxidant activities. Major phenolic acids identified in the extracts of these celeries were caffeic acid,  p -coumaric acid, and ferulic acid, while the identified flavonoids were apigenin, luteolin, and kaempferol. The contents of total phenolics were measured using a Folin–Ciocalteu assay and the total antioxidant capacity was estimated by the 1, 1-diphenyl-2-picrylhydrazyl radical (DPPH) and 2, 2'-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS·⁺) methods. Apigenin was the major flavonoid in these samples and the most abundant phenolic acid was  p- coumaric acid. Many of the investigated cultivars had high levels of phenolics and exhibited high antioxidant capacity. Among these 11 cultivars, Shengjie celery had the highest antioxidant activity whereas Tropica had the lowest. An extremely significant positive correlation between the antioxidant activity and the contents of total flavonoids, total phenolic acids, or total phenolics was observed in this study.     

Phenolic Profiles and Total Antioxidant Capacity of Marketed Beers in Serbia

The aim of this research was to determine the total phenolic and flavonoid contents as well as to measure antioxidant activity of 24 different commercial beers consumed in Serbia. The major phenolic acids (gallic acid, protocatechuic acid, 4-hydroxybenzoic acid, 2,5-dihydroxybenzoic acid, vanillic acid, caffeic acid, syringic acid, p-coumaric acid, ferulic acid, sinapic acid, salicylic), (+)-catechin, and (-)-epicatechin were also determined by high pressure liquid chromatography method using a photodiode array detector. Gallic acid, ferulic acid, and protocatechuic acid are the most abundant phenolic acids in all samples, followed by (+)-catechin. The total phenolic content was determined using the Folin-Ciocalteu assay. The total flavonoids were measured using spectrophotometrics as the aluminum chloride assay. The results showed that the highest total phenolic and flavonoid contents were established in dark and light beer samples. 2,2-Diphenyl-1-picrylhidrazyl radical scavenging activity, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) radical cation scavenging activity, and ferric reducing/antioxidant power were used to assess the antioxidant potential of beers. These assays, based on different chemical mechanisms, were selected to take into account the wide variety and range of action of antioxidant compounds present in selected beer samples. All beers showed antioxidant power, but a wide range of antioxidant capacities was observed. Statistical differences between ferric reducing-antioxidant power and the other two antioxidant capacity assays were confirmed. This study will be useful for the appraisal of phenolic profile and antioxidant activities of various beers, and it will also be of interest for people who like drinking this beverage.     

Phytochemicals and antioxidant activity of different fruit fractions (peel,pulp, aril and seed) of Thai gac (Momordica cochinchinensis Spreng)

Three fractions (peel, pulp and aril) of gac fruit (Momordica cochinchinensis Spreng) were investigated for their phytochemicals (lycopene, beta-carotene, lutein and phenolic compounds) and their antioxidant activity. The results showed that the aril had the highest contents for both lycopene and beta-carotene, whilst peel (yellow) contained the highest amount of lutein. Two major phenolic acid groups: hydroxybenzoic acids and hydroxycinnamic were identified and quantified. Gallic acid and p-hydroxybenzoic acid were found in all fractions. Ferulic acid and p-hydroxybenzoic acid were most evident in pulp. Myricetin was the only flavonoid found in all fractions. Apigenin was the most predominant flavonoid in pulp (red), whereas rutin and luteolin gave the highest content in aril. The extracts of different fractions exhibited different levels of antioxidant activity in the systems tested. The aril extract showed the highest FRAP value. The greatest antioxidant activities of peel and pulp extracts were at immature stage, whereas those in the seed extracts increased from mature stage to ripe stage. The contents of total phenolic and total flavonoid in peel and pulp decreased during the fruit development stage (immature > ripe fruit) and subsequently displayed lower antioxidant capacity, except for the seed.     

Changes in bioactive compounds and antioxidant activity during convective drying of murta (Ugni molinae T.) berries

Murta (Ugni molinae T.) berries were air‐dried at five temperatures (40, 50, 60, 70 and 80 °C), and the changes in β‐carotene, phenolic acids, total phenolic and flavonoid contents and antioxidant capacities (DPPH and ORAC) were investigated. The berries showed a high content of β‐carotene, which decreased during drying temperature between 40 °C and 80 °C. Free and bound phenolic acids were also determined, showing gallic acid to be the prevalent phenolic acid. Total phenolic and flavonoid contents in the dried berries showed a higher decrease at lower temperature due to longer drying time. The radical‐scavenging activity also showed higher antioxidant activity at higher drying temperatures (70–80 °C) than at lower drying temperatures (40–50 °C). Total phenolic content (TPC) and flavonoids showed good correlation with antioxidant capacity. Murta berries proved to be an excellent source of antioxidants and bioactive compounds and are therefore a potential ingredient for new functional food products.     

Antioxidant capacities,procyanidins and pigments in avocados of different strains and cultivars

Avocado (Persea americana) is an important tropical fruit, but little is known about their antioxidant capacities and phytochemical composition. The objective of this research was to determine antioxidant capacities, total phenolic content and identify and quantify major antioxidant compounds in avocados of different strains and cultivars. Ripe Florida avocados from seven cultivars (Slimcado, Booth 7, Booth 8, Choquette, Loretta, Simmonds, and Tonnage) of West Indian or Guatemalan strains were separated into seeds, peels and pulp, and freeze dried. Hass avocado of Mexican strain was chosen for comparison. Samples were extracted with acetone/water/acetic acid solvent and analysed using the Folin–Ciocalteu assay for total phenolic content. Antioxidant capacities were determined by oxygen radical absorbance capacity (ORAC) and DPPH assays. Procyanidins were identified and quantified using HPLC-MSⁿ. Antioxidant pigments (chlorophylls and carotenoids) were estimated spectrophotometrically. For all varieties, seeds contained the highest antioxidant capacities, phenolic content, and procyanidins, whereas the pulp had the lowest. Procyanidins, including catechin, epicatechin, A- and B-type dimers, A- and B-type trimers, tetramers, pentamers and hexamers, were identified in peels and seeds using normal-phase HPLC–ESI-MSⁿ. Antioxidant capacities, phenolic contents and procyanidins in avocados were highly correlated, suggesting that procyanidins were the major phenolic compounds that contributed to antioxidant capacities. Carotenoids and chlorophylls were found to be concentrated in avocado peels but did not correlate with antioxidant capacities. This study suggested that avocado seeds and peels, industrial wastes of avocado processing, can be exploited as source of antioxidants.     

Liaison of phenolic acids and biological activity of escalating cultivars of Daucus carota

The objective of the present study was to analyze and compare the phenolic compounds and their antioxidant capacities of new lines of Dacus carota. The selected cultivars showed high variation in the contents of total phenolics (30.26–65.39 mg/100 g FW) and total ascorbic acid (41.12–58.36 mg/100 g FW). Analysis on RP-HPLC revealed that hydroxycinnamic acids and its derivatives were major phenolic compounds present in D. carota extracts, whereas 5-caffeolquinic acid was a major hydroxycinnamic acid (ranged from 30.26 to 65.39 mg/100 g FW). DCP cultivar showed high total antioxidant capacity (77.69 mg/100 g), 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging capacity (52.36 mg/100 g), superoxide radical scavenging capacity (53.69 mg/100 g), and hydroxyl radical scavenging capacity (51.91 mg/100 g). A linear relationship was found between total phenolic acid contents and antioxidant capacity. Both phenolic compounds and antioxidant capacities varied significantly (ρ < 0.05) among cultivars. DCP cultivar was found to be a rich source of phenolics and ascorbic acid with high antioxidant activity.     

Antioxidant activity and phenolic compounds of ginger (<Emphasis Type="Italic">Zingiber officinale</Emphasis> Rosc.) determined by HPLC-MS/MS

Oxidative stress related diseases often arise from over production of free radicals and reactive oxygen/nitrogen species. The prevention of these diseases could be possible with the use of natural antioxidant plants that could be promising as therapeutic candidates. Since antioxidant properties of a species could be stem from phenolic compounds, it is, therefore, important to evaluate antioxidant and total/individual phenolic and flavonoid content. For this purpose, we evaluated antioxidant properties of ginger (Zingiber officinale Rosc.) based on three parameters: the antioxidant capacity, total phenolic and flavonoid content as well as identification of phenolic acids of water extract (WEG) and ethanol extract (EEG) of ginger. For antioxidant capacity, we performed FRAP, CUPRAC assay, Fe²⁺ chelating ability, DPPH and DMPD radical scavenging activities. Also, total phenolic and flavonoid contents in both extracts were also measured via Folin Ciocalteu’s method. For identification of phenolic acids, HPLC-MS/MS method was performed. The results showed that EEG had generally better antioxidant activity than WEG in all assays. HPLC-MS/MS analysis showed that there are at least eight different phenolic acids found in ginger, among which pyrogallol p-hydroxybenzoic acid, ferulic acid and p-coumaric acid were more abundant in both extracts. This study clearly showed that ginger extracts demonstrated effective antioxidant properties and their consumption may reduce or delay the progression of diseases that oxidative stress take place due to lack of antioxidant supplementation.     

Changes of phenolic acids and antioxidant activities during potherb mustard (Brassica juncea, Coss.) pickling

Phenolic acids in potherb mustard (Brassica juncea, Coss.) were determined and the effects of pickling methods on the contents of total free phenolic acids, total phenolic acids, total phenolics, and antioxidant activities were investigated. Gallic acid, protocatechuic acid, p-hydroxybenzoic acid, vanillic acid, caffeic acid, p-coumaric acid, ferulic acid, and sinapic acid were identified in the present study. The contents of total free phenolic acids, total phenolic acids and total phenolics in fresh potherb mustard were 84.8 ± 0.58 μg/g dry weight (DW), 539 ± 1.36 μg/g DW, and 7.95 ± 0.28 mg/g DW, respectively. The total free phenolic acids increased during the pickling processes, but the total phenolic acids, total phenolics, and antioxidant activities decreased. However, after 5 weeks of fermentation, all the pickling methods retained over 70% of total phenolic contents and above 65% of antioxidant capacities. The results indicated that pickling processes were relatively good methods for the preservation of phenolic acids and antioxidants for potherb mustard.     

Antiproliferative and antioxidant activities of Turkish pomegranate (Punica granatum L.) accessions

The objective of this study was to assess antioxidant and antiproliferative activities of four different Turkish pomegranate varieties (Hatay, Hicaz, Adana and Antalya) using an in vitro HepG2 cancer cell model. All the pomegranate extracts employed in this study significantly diminish the proliferation of HepG2 cells in a dose‐dependent manner. The total phenolic acid, anthocyanin and flavonoid contents for each of the four varieties were determined. The Hatay pomegranate variety had the highest total phenolic acid (337.4 ± 2.34 mg/100 g) and flavonoid (58.42 ± 2.25 mg/100 g) contents of the pomegranates examined. Antioxidant activities of the pomegranates were determined using DPPH and ABTS radical scavenging assays. The lack of correlation between colour index value and antioxidant–antiproliferative activities suggested that phenolic acids and flavonoids are predominant compounds influencing pomegranate's bioactivity rather than anthocyanins. Individual phenolic acids found in Hatay pomegranates were determined, using an HPLC system, as gallic acid being the most predominant phenolic compound.     

Comparison of phenolic compound contents and antioxidant capacities of loquat (Eriobotrya japonica Lindl.) fruits

The characteristics, phenolic compound contants, and antioxidant capacities of 6 cultivars of loquat fruit grown in China were evaluated. HPLC was used to identify and quantify phenolics. Chlorogenic acid, neochlorogenic acid, 4-O-caffeoylquinic acid, protocatechuic acid, 4-hydroxybenzoic acid, caffeic acid, ferulic acid, ellagic acid, and o-coumaric acid were the main phenolic compounds of mature loquat fruits. Contents of chlorogenic acid, neochlorogenic acid, 4-hydroxybenzoic acid, protocatechuic acid, and o-coumaric acid were all significantly correlated with antioxidant capacities determined using DPPH, ABTS radical scavenging activity, and ferric reducing/antioxidant power assays. The ‘Taxiahong’ cultivar contained the highest amounts of total phenolics and flavonoids and the highest antioxidant capacity, while ‘Taipingbai’ showed the lowest. The high level of phenolic compounds and antioxidant capacities of some cultivars indicates that these cultivars can be sources of bioactive compounds that are relevant to human health.     

Comparative study of total phenolic compounds,flavonoids and antioxidant capacities in pigmented and non-pigmented rice of <Emphasis Type="Italic">indica</Emphasis> rice varieties

The total phenolic compounds and flavonoid contents of grains as well as the antioxidant capacities were determined in 15 rice varieties. A high-performance liquid chromatography method was modified for the determination of the flavonoid subgroups in rice grains. The results showed the total phenolic compounds, flavonoid contents, and antioxidant capacities of pigmented rice were higher than in non-pigmented rice. The amounts of flavanone groups ranging from 0.04 to 0.40 mg Naringenin g^?1, while flavones groups ranging from 0.08 to 0.57 mg Apigenin g^?1, flavonol groups ranging from 0.16 to 1.20 mg Quercetin g^?1 and anthocyanin groups ranging from 44.43 to 69.83 mg Cyanidin chloride g^?1 were found in pigmented rice. The total phenolic compounds and total flavonoid contents of grains were significantly correlated with their antioxidant capacities. The results indicated that pigmented rice appeared as a good source of phenolic and flavonoid compounds and had beneficial nutritive values or antioxidant substances.     

Phenolic profiles and cellular antioxidant activity of longan pulp of 24 representative Chinese cultivars

The phytochemical composition and antioxidant activity of fruits are associated with their health benefits. Longan is a traditional Chinese edible and medicinal fruit, but its varietal differences in phytochemical profiles and antioxidant activity were unknown. Twenty-four longan cultivars from southern China were investigated in this study. Their total phenolic and flavonoid contents in pulp were 22.09–132.47 mg gallic acid equivalents/100 g and 2.48–14.26 mg catechin equivalents/100 g, respectively. The mean contributions of free phenolics and ?avonoids to the total were 82.5% and 94.0%, respectively. Among 10 individual phenolics detected by HPLC, the contents of epicatechin, 4-methylcatechol, chlorogenic, and vanillic acids were relatively higher. The cellular antioxidant activity (CAA) of longan pulp showed significant varietal discrepancies and positive correlation with phenolic and flavonoid contents. Phenolics in longan pulp of 24 cultivars showed lower CAA potential than many other fruits with the CAA qualities from 0.35 to 1.21 µmol quercetin equivalent/100 µmol total phenolics. Longan cultivars were classified into six groups by hierarchical clustering analysis. Six cultivars in group 4 and 6 had higher phytochemical contents and CAA activity.     

A comparative study on free and bound phenolic acid content and their antioxidant activity in bran of rice (Oryza sativa L.) cultivars of Eastern Himalayan range

In our study, seven most prevailing but unexplored indigenous rice cultivars of northeast India, situated in the Eastern Himalayan Range, were investigated for their phenolic acid profile, total phenolic content (TPC) and antioxidant capacities in free and bound phenolic extracts of their bran. HPLC studies showed the presence of ferulic, p‐coumaric, sinapic, caffeic, chlorogenic and vanillic acids, with ferulic and p‐coumaric acids being the dominant phenolic acids in the bound form. The lower EC₅₀ values of the bound extracts than the free extracts suggested the better radical scavenging activity of the bound extracts. Significant correlations were observed between TPC and phenolic acid content (HPLC‐DAD) of bound extracts, and between Trolox equivalents antioxidant capacity (TEAC) and phenolic acid content (HPLC‐DAD) of both free and bound extracts. The findings suggest that phenolic acids in the rice cultivars investigated were exclusively present in bound form and contribute significantly towards their antioxidant capacity.     

Determination of phenolic composition and antioxidant capacity of blood orange juices obtained from cvs. Moro and Sanguinello (Citrus sinensis (L.) Osbeck) grown in Turkey

The phenolic compounds and antioxidant capacities of orange juices obtained from cvs. Moro and Sanguinello (Citrus sinensis (L.) Osbeck) were determined. A high-performance liquid chromatographic method coupled with diode-array detection was used to identify and quantify phenolic compounds of the orange juices. A total of 18 phenolic compounds were identified and quantified in Moro and Sanguinello orange juices, including hydroxybenzoic acids (2), hydroxycinnamic acids (5), flavanones (5), and anthocyanins (6). It was observed that total phenolic content of Moro juice was higher than that of Sanguinello juice. Ferulic acid was the most dominant hydroxycinnamic acid and cyanidin 3-(6″-malonyl glucoside) and cyanidin 3-glucoside were the most dominant anthocyanins in both cultivars. Antioxidant activities of orange juices were measured using the DPPH^· (2,2-diphenyl-1-picrylhydrazyl) method. According to DPPH^· assays, the antioxidant capacity of Moro juice was found to be higher than that of Sanguinello juice.     

Assessment of the antioxidant potential and fatty acid composition of four Centaurea L. taxa from Turkey

This paper focused on the assessment of antioxidant property and fatty acid composition of four Centaurea species. The antioxidant activity of its methanol extract was evaluated by several in vitro experiments including phosphomolybedum assay, DPPH assay, β-carotene/linoleic acid, ferric and cupric reducing power. Total phenolic and flavonoid contents were also evaluated. The methanol extract of Centaurea pulcherrima var. pulcherrima showed the superior free radical scavenging activity, linoleic acid inhibition capacity, reducing power and also had the highest total phenolic content. A significant relationship between antioxidant capacity and total phenolic components was found. The oils of Centaurea taxa were also analysed for fatty acid concentration by gas chromatography. The principal fatty acids in the species were palmitic acid (23.38–30.49%) and linoleic acid (20.19–29.93%). These findings suggest that the Centaurea species could be used as a potential source of new natural antioxidants and unsaturated fatty acids in food industry, cosmetics and pharmaceutical preparations.     

Variations in phenolic composition and antioxidant properties among 15 basil (Ocimum basilicum L.) cultivars

In this study, the influences of cultivar on the phenolic composition and antioxidant properties of 15 different basil varieties was determined. Cultivar had a statistically significant effect on total phenolic levels (p < 0.001) and anthocyanin concentrations (p < 0.001). Analysis of individual phenolic acid levels by high-performance liquid chromatography showed substantial variations in the phenolic acid profiles among cultivars. Rosmarinic (p < 0.001), chicoric (p = 0.002) and caffeic (p = 0.001) acid concentrations were affected by cultivar, although caftaric acid levels (p = 0.083) were not. Nine of the cultivars in this study contained chicoric acid in higher concentrations than rosmarinic acid. These are the first basil cultivars that have been identified in which rosmarinic acid is not the dominant phenolic acid. In addition, six of the cultivars in this study had caftaric and caffeic acid concentrations that were similar or higher than rosmarinic acid levels. Cultivar also had a significant impact on both FRAP (ferric reducing antioxidant power, p = 0.007) and DPPH (2,2′-diphenyl-1-picrylhydrazyl, p = 0.004) antioxidant capacities. For the basil cultivars in this study, the individual phenolic acid composition was found to be an important factor influencing the measured antioxidant capacity.     

Effect of lactic acid fermentation on antioxidant properties and phenolic acid contents of oyster (<Emphasis Type="Italic">Pleurotus ostreatus</Emphasis>) and chanterelle (<Emphasis Type="Italic">Cantharellus cibarius</Emphasis>) mushrooms

Fruiting bodies of Pleurotus ostreatus (oyster) and Cantharellus cibarius (chanterelle) mushrooms underwent acid fermentation using 3 strains of lactic acid bacteria (LAB) as starter cultures. Polyphenol contents, antioxidant activities, and phenolic acid contents in fresh, blanched, and fermented mushrooms were investigated. Fruiting bodies of oyster mushrooms exhibited higher total phenolic contents than chanterelle mushrooms. Blanching caused a decrease in polyphenol contents and antioxidant activities in both mushroom types. No important differences were observed in total phenolic compound contents (measured using Folin-Ciocalteau reagent) in mushrooms using different LAB strains. Lactobacillus plantarum was the most useful microorganism for lactic acid fermentation of fruiting bodies for reduction of the pH value. The highest concentrations of single phenolic acids: gallic, homogentisic, and ferulic acids were present in mushrooms fermented using L. plantarum.     

Phenolic Composition,Essential Oil,and Antioxidant Activity in the Aerial Part of Artemisia Herba-Alba from Several Provenances: A Comparative Study

This study characterized the phenolic, aroma compositions, and antioxidant capacities of four Artemisia herba alba accessions collected from north and center regions in Tunisia in order to select valuable origin with optimal bioactive compounds production. The total polyphenol and flavonoid contents varied between accessions with maxima contents observed in center regions. Kaempherol, apigenin, naringenin, p-coumaric, trans-cinnamic, and caffeic acids were the most abundant compounds with percentage varying depending on the considered accession. Significant changes on essential oil yields (0.4–1.2%) were found between accessions and three different oil chemotypes were distinguished: camphor, fenchol/α-thujone, and α-thujone/camphor. Cluster analysis of volatile and phenolic compositions grouped the accessions on different groups. Antioxidant activities of extracts were found to be higher than essential oils for the four provenances. The results suggested that the center regions have high potential for selecting varieties rich on essential oil, antioxidant phenolic acids, and flavonoids.     

Flavonoid constituents and their contribution to antioxidant activity in cultivars and hybrids of rabbiteye blueberry (Vaccinium ashei Reade)

Fruit from 42 blueberry (Vaccinium spp.) cultivars, including 36 rabbiteye cultivars (Vaccinium ashei Reade), three V. ashei hybrid derivatives, and three northern highbush (Vaccinium corymbosum L.) standards were evaluated for antioxidant capacity, individual flavonoid content, and the contribution of each identified phenolic compound to total antioxidant activity. Considerable variation was found in flavonoid content, antioxidant activity, and their contribution to total antioxidant activity among cultivars. Among 42 blueberry cultivars, the rabbiteye ‘Early May’ contained the highest amount of chlorogenic acid, myricetin 3-arabinoside, quercetin derivatives, and delphinidin-, cyanidin-, petunidin-, and malvidin-basis anthocyanins. ‘Early May’ cultivar also had the highest antioxidant activity (88.2 μmol TE/g fw). ‘Owen’, ‘Bluegem’, ‘Clara’, Climax’, and ‘Centurion’ were among the other rabbiteye cultivars that also had high levels of flavonoids and antioxidant activities. In contrast, the pink-fruited V. ashei hybrid, ‘Pink Lemonade’, had the lowest content of flavonoids and lowest antioxidant activity. The mean flavonoid content and antioxidant activity of rabbiteye cultivars was higher than those among northern highbush and V. ashei hybrids. The antioxidant activity of V. ashei hybrid derivatives was derived mainly from chlorogenic acid, myricetin, and quercetin, which contributed 62.5% of total antioxidant activity, whereas anthocyanins (malvidin, petunidin, delphinidin, and cyanidin) were the main contributors to the antioxidant activity of rabbiteye cultivars (76.2%) and northern highbush standards (76.8%). Blueberry cultivars identified to have high phenolic content and high antioxidant activity could be used as parents for future blueberry breeding programmes to develop new blueberry cultivars with higher antioxidant activity and further improve human health.