Antioxidative stress activity of oligophosphopeptides derived from hen egg yolk phosvitin in Caco-2 cells

The protective effects of hen egg yolk phosvitin phosphopeptides (PPPs) against hydrogen peroxide (H2O2)-induced oxidative stress were evaluated in an in vitro assay using human intestinal epithelial cells. Caco-2 cells were stimulated with 1 mM H2O2 for 6 h, and the secretion of IL-8, a proinflammatory mediator, was determined by ELISA as a biomarker of oxidative stress. The inhibition of H2O2-induced IL-8 secretion from Caco-2 cells was observed by pretreatment for 2 h with PPPs, but not with phosvitin. PPPs also suppressed the formation of malondialdehyde in H2O2-treated Caco-2 cells. Furthermore, intracellular glutathione levels and glutathione reductase activity were elevated by the addition of PPPs. The protective effects of PPPs against H2O2-induced oxidative stress were almost the same as that of glutathione, and PPPs with a high content of phosphorus exhibited higher protective activity than PPPs without phosphorus; however, phosphoserine itself did not show any significant antioxidative stress activity. These findings suggest that oligophosphopeptides from hen egg yolk phosvitin possess novel antioxidative activity against oxidative stress in intestinal epithelial cells and that phosphorus and peptide structure seem to have a key role in the activity.     

Antioxidative activity of amino acids on tissue oxidative stress in human intestinal epithelial cell model

The protective effects of amino acids against H 2O 2-induced oxidative stress were investigated in an in vitro assay using human intestinal epithelial cells. Caco-2 cells were pretreated with amino acids (1, 2, and 5 mM) for 2 h and then stimulated with 1 mM H 2O 2 for 6 h. The secretion of IL-8, a proinflammatory mediator, was determined by ELISA as an indicator of tissue oxidative stress. The inhibition of H 2O 2-induced IL-8 secretion from Caco-2 cells was observed by pretreatment with Cys, Val, Ile, Leu, Trp, His, Lys, and Ala. Cys enhanced glutathione (GSH) biosynthesis enzyme activity and increased cellular GSH levels. Branched-chain amino acids such as Val, Ile, and Leu elevated activities of GSH S-transferase (GST) and catalase. Trp, His, and Lys caused increases in GST activity. Ala enhanced GSH reductase activity. These data suggest that specific amino acids exert protective effects against tissue oxidative stress in intestinal epithelial cells based on the structure.     

Specific immunomodulatory and secretory activities of stevioside and steviol in intestinal cells

Stevioside, isolated from Stevia rebaudiana, is a commercial sweetener. It was previously demonstrated that stevioside attenuates NF-kappaB-dependent TNF-alpha and IL-1beta synthesis in LPS-stimulated monocytes. The present study examined the effects of stevioside and its metabolite, steviol, on human colon carcinoma cell lines. High concentrations of stevioside (2-5 mM) and steviol (0.2-0.8 mM) decreased cell viability in T84, Caco-2, and HT29 cells. Stevioside (2 mM) potentiated TNF-alpha-mediated IL-8 release in T84 cells. However, steviol (0.01-0.2 mM) significantly suppressed TNF-alpha-induced IL-8 release in all three cell lines. In T84 cells, steviol attenuated TNF-alpha-stimulated IkappaB --> NF-kappaB signaling. Chloride transport was stimulated by steviol (0.1 mM) > stevioside (1 mM) at 30 min. Two biological effects of steviol in the colon are demonstrated for the first time: stimulation of Cl(-) secretion and attenuation of TNF-alpha-stimulated IL-8 production. The immunomodulatory effects of steviol appear to involve NF-kappaB signaling. In contrast, at nontoxic concentrations stevioside affects only Cl(-) secretion.     

Antiproliferative effects of dietary phenolic substances and hydrogen peroxide

There has been controversy as to whether the antiproliferative activity of dietary phenolic substances on cancer cells is due to the bioactivities of phenolics or the generation of hydrogen peroxide (H2O2) in media as an artifact. This study was to investigate whether the formation of H2O2 by different phenolics induces acute toxicity and carcinogenicity in normal rat liver epithelial cells. Gallic acid, one of the major antioxidants present in fruits and vegetables, dose-dependently generated considerably more H2O2 in DMEM media without cells than did quercetin. Gallic acid exerted stronger antiproliferative activity than quercetin on both Caco-2 human colon cancer cells (Caco-2 cells) and WB-F344 normal rat liver epithelial cells (WB cells) cultured in DMEM media, and the effect was partially reduced by catalase. Furthermore, gallic acid (but not quercetin) also inhibited gap-junction intercellular communication (GJIC; a carcinogenic phenomenon), which was in part protected by the addition of catalase. Exogenous H2O2 addition also inhibited the proliferation of both Caco-2 cells and WB cells and inhibited GJIC in a dose-dependent manner, but these effects were almost abolished by the treatment with catalase. From these results it is concluded that the antiproliferative effects of some antioxidants on cancer cells are partially due to their prooxidant actions.     

Deodorization with ku-ding-cha containing a large amount of caffeoyl quinic acid derivatives

Caffeoyl quinic acid (CQA) derivatives in ku-ding-cha, mate, coffee, and related plants were determined by HPLC. One ku-ding-cha contained a large amount of 3,5-dicaffeoylquinic acid (3,5-diCQA, 10.6% in dry weight) as well as 3-CQA (1.7%), 4-CQA (1.1%), 5-CQA (6.3%), 3,4-diCQA (1.8%), and 4,5-diCQA (4.3%). In this ku-ding-cha, the total caffeic acid moiety was 90.3 mmol/100 g of dry weight. The leaves of Ilex latifolia, which is one original species of ku-ding-cha, and another plant of the same genus, I. rotunda, also contained 3,5-diCQA (9.5 and 14.6%), 3-CQA (4.3 and 1.9%), and 5-CQA (4.8 and 3.8%), respectively, whereas raw coffee bean contained 5.5% 5-CQA and other low CQA derivatives. 3,5-DiCQA and 5-CQA with an apple acetone powder (AP) containing polyphenol oxidase showed high capturing activities toward thiols, and two addition compounds between 3,5-diCQA and methane thiol were also identified. Ku-ding-cha indicated extremely strong capturing activities toward methanethiol, propanethiol, and 2-propenethiol in the presence of apple AP. Furthermore, drinking ku-ding-cha reduced the amount of allyl methyl sulfide gas, well-known to persist as malodorous breath long after the ingestion of garlic.     

Effect of 2alpha-hydroxyursolic acid on NF-kappaB activation induced by TNF-alpha in human breast cancer MCF-7 cells

Apples are one of the largest contributors of fruit phenolics of all fruits consumed by Americans and contain a variety of bioactive compounds, which have health benefits. Consumption of apples has been linked to reduced risk of chronic diseases such as cancer and cardiovascular disease. Apple extracts have been shown to have the capabilities of inhibiting NF-kappaB activation in human breast cancer MCF-7 cells. 2Alpha-hydroxyursolic acid is one of the major triterpenoids isolated from apple peels, and its effects on cell proliferation and TNF-alpha-induced NF-kappaB activation in MCF-7 cells were examined. 2Alpha-hydroxyursolic acid significantly inhibited MCF-7 cell proliferation at doses of 20 microM (p < 0.05). Preincubation with 2alpha-hydroxyursolic acid suppressed TNF-alpha-induced NF-kappaB activation in a dose-dependent manner and significantly inhibited the activation at a dose of 20 microM of 2alpha-hydroxyursolic acid (p < 0.05). 2Alpha-hydroxyursolic acid treatment did not affect the phosphorylation level of NF-kappaB inhibitor (IkappaB-alpha), but proteasome activity in MCF-7 cells was inhibited significantly at doses of 10 and 20 microM ( p < 0.05). These results suggest that 2alpha-hydroxyursolic acid has antiproliferative activities against MCF-7 cells and capabilities inhibiting NF-kappaB activation induced by TNF-alpha partially by suppressing proteasome activities.     

Oligophosphopeptides derived from egg yolk phosvitin up-regulate gamma-glutamylcysteine synthetase and antioxidant enzymes against oxidative stress in Caco-2 cells

Previously, we have found phosphopeptides (PPPs) from hen egg yolk phosvitin possess a potent antioxidative activity against oxidative stress in human intestinal epithelial cells, Caco-2. However, their biological activity at the cellular level has not yet fully understood. The objective of this study is to evaluate the regulation of glutathione (GSH) biosynthesis-associated and antioxidant enzymes against oxidative stress in Caco-2 cells using an in vitro model. Treatment of 1 mM H2O2-induced Caco-2 cells with PPPs increased cellular GSH levels, concomitant with a significant increase in gamma-glutamylcysteine synthetase (gamma-GCS) activity and the expression of gamma-GCS heavy subunit mRNA. Furthermore, intracellular glutathione reductase, glutathione S-transferase, and catalase activities were elevated by PPPs. In addition, PPPs with high content of phosphorus showed higher induction of these enzyme activities than PPPs without phosphorus. These data indicate that oligophosphopeptides from hen egg yolk phosvitin can up-regulate cellular GSH biosynthesis-associated enzymes activity and antioxidative activities, which play key roles against tissue oxidative stress in the human intestinal epithelial cells.     

Chlorogenic acid in coffee can prevent the formation of dinitrogen trioxide by scavenging nitrogen dioxide generated in the human oral cavity

Coffee contains antioxidants like chlorogenic acid and its isomers. In this report, effects of coffee on the nitrite-induced N2O3 formation were studied using whole saliva and bacterial fraction prepared from the saliva. The formation of N2O3 was measured by fluorescence increase due to the transformation of 4,5-diaminofluorescein to triazolfluorescein. Coffee inhibited the nitrite-induced fluorescence increase, and 50% inhibition was observed at several microg of coffee/mL in bacterial fraction of saliva as well as whole saliva. During the inhibition of the fluorescence increase, concentration of chlorogenic acid and its isomers decreased. It is discussed that the reduction of NO2 by chlorogenic acid and its isomers contributed to the coffee-dependent inhibition of the fluorescence increase as N2O3 is formed from NO and NO2. When coffee was added to whole saliva, chlorogenic acid and its isomers bound to cells in the saliva. The rate of the fluorescence increase in bacterial fraction, which was prepared at defined periods after the ingestion of coffee, was increased to the rate before the ingestion of coffee with a half-time of about 1 h. This result suggests that chlorogenic acid and its isomers remained in the oral cavity for a few hours after ingestion of coffee. The significance of coffee drinking and rinsing of the mouth with coffee for the health of the oral cavity is proposed.     

Identification of hen egg yolk-derived phosvitin phosphopeptides and their effects on gene expression profiling against oxidative stress-induced Caco-2 cells

Oxidative stress is involved in the initiation and propagation of chronic intestinal pathologies. Bioactive peptides such as egg yolk-derived phosvitin phosphopeptides (PPP3) have been previously shown to reduce in vitro oxidative stress by up-regulating glutathione synthesis and antioxidant enzyme activities. Peptide and gene expression profile analysis of the PPP3 peptides can provide insight into structures involved in signal transduction mechanisms in the antioxidative stress response. The objectives of this research were to identify the PPP3 amino acid sequences before and after simulated gastrointestinal digestion and to assess the genes influenced by PPP3. Peptide sequences were analyzed using ESI Q-TOF-MS/MS, and the expression profile of 84 human oxidative stress and antioxidant defense genes were analyzed. Undigested PPP3 was composed of three main peptides: GTEPDAKTSSSSSSASSTATSSSSSSASSPNRKKPMDE (phosvitin-PV residues 4-41), NSKSSSSSSKSSSSSSRSRSSSKSSSSSSSSSSSSSSKSSSSR (PV residues 155-197), and EDDSSSSSSSSVLSKIWGRHEIYQ (PV residues 244-257) and their fragments. There was limited degradation of PPP3 after gastrointestinal digestion as deduced from the fragment sizes of digested PPP3, which ranged from 5 to 32 amino acids. These fragments were rich in contiguous serines and, in some cases, monoesterified with phosphate. Both undigested and digested PPP3 significantly reduced IL-8 secretion in H(2)O(2)-induced Caco-2 cells, indicating that antioxidative stress bioactivity is retained upon digestion. After PPP3 pretreatment, antioxidant genes associated with oxygen and reactive oxygen species (ROS) metabolism and cellular responses to chemical stimulus, oxidative stress, and ROS are up-regulated in the presence and absence of oxidative stress, thereby contributing to the prevention of intestinal oxidative stress and the promotion of gut health.     

Caffeic acid disturbs monocyte adhesion onto cultured endothelial cells stimulated by adipokine resistin

Adipokines have been implicated in the pathogenesis of atherosclerosis via pro-inflammatory mechanisms contributing to insulin resistance. The adipokine resistin causes endothelium dysfunction, which plays an important role in sustaining atherogenesis. This study investigated whether resistin induced expression of cell adhesion molecules and integrins in endothelial cells and THP-1 monocytes and whether such induction was attenuated by 1-20 μM caffeic acid. Resistin enhanced endothelial expression of vascular cell adhesion molecule 1 (VCAM-1), intercellular cell adhesion molecule 1 (ICAM-1), and E-selectin and monocyte expression of β1, β2, and α4 integrins. The enhancement of these proteins was diminished by caffeic acid with reduced THP-1 cell adhesion on activated endothelium. Caffeic acid at ≤20 μM demoted resistin-stimulated interleukin 8 (IL-8) production responsible for ICAM-1 and β2 integrin induction. The endothelial up-regulation of IL-8 secretion by resistin entailed toll-like receptor 4 (TLR4) activation, but caffeic acid diminished IL-8 production and TLR4 induction. Furthermore, caffeic acid encumbered resistin-activated nuclear factor κB (NF-κB) signaling. These results demonstrate that caffeic acid blocked monocyte trafficking to resistin-activated endothelium via disturbing NF-κB signaling responsive to IL-8. Therefore, caffeic acid may have therapeutic potential in preventing obesity-associated atherosclerosis.     

Pharmacokinetic study of caffeic and rosmarinic acids in rats after oral administration

p-Coumaric and ferulic acid are actively taken up by monocarboxylic acid transporter (MCT), whereas gallic acid, caffeic acid (CA), and rosmarinic acid (RA) are absorbed by paracellular diffusion in human intestinal Caco-2 cells, although CA has low affinity for MCT. We previously demonstrated that p-coumaric acid has a much higher absorption efficiency than gallic acid in rats, owing to the MCT-mediated absorption of p-coumaric acid in vivo (J. Agric. Food Chem. 2004, 52, 2527-2532). Here, absorption of orally administered CA and RA in rats has been studied to investigate their intestinal absorption characteristics and pharmacokinetics in vivo and to compare the results with those of p-coumaric and gallic acids obtained under identical conditions. Rats were given 100 micromol/kg body weight of CA and RA, and blood was collected from the portal vein and abdominal artery after administration. CA, RA, and their metabolites were quantified by a coulometric detection method using HPLC-ECD. The serum concentration of intact CA and RA in the portal vein peaked at 10 min after administration, with a C(max) of 11.24 micromol/L for CA and 1.36 micromol/L for RA. The area under the curve (AUC) for intact CA and RA in the portal vein was calculated from the serum concentration-time profile to be 585.0 and 60.4 micromol min L-1, respectively. The absorption efficiency of CA was about 9.7-fold higher than that of RA. Overall, the absorption efficiency of these compounds in vivo increases in the order: gallic acid = RA < CA < p-coumaric acid, which is in good agreement with results obtained in Caco-2 cells in vitro.     

Antiproliferative activity of apples is not due to phenolic-induced hydrogen peroxide formation

Anticancer compound screening of natural products using tumor cell lines has been commonly used to identify anticancer drugs. Two highly significant anticancer drugs, paclitaxel (Taxol) and camptothecin, were discovered using tumor cell lines by the U.S. National Cancer Institute (NCI) screening program of plants. It has been recently reported that the inhibition of cancer cell proliferation by fruit extracts was indirectly caused by phenolic-induced H(2)O(2) production in the cell culture media, suggesting that many previously reported effects of flavonoids and phenolic compounds on cultured cells might be from an artifact of H(2)O(2)-induced oxidative stress. The objective of the present study was to determine if apple extracts induced H(2)O(2) formation in common cell culture media and to investigate if the antiproliferative activity of apple extracts was due to phenolic-induced H(2)O(2) formation. It is reported here that apple extracts did not induce H(2)O(2) formation in WME, DMEM, or DMEM/Ham F12 media with the cell culture conditions tested. These same extracts inhibited proliferation of HepG(2) and Caco-2 cells. Therefore, antiproliferative activity of apple extracts was not due to the phenolic-induced H(2)O(2) production in cell culture media. In addition, H(2)O(2) added to the culture medium at 100 microM did not cause inhibition of cell proliferation in either HepG(2) liver cancer cells or Caco-2 colon cancer cells in vitro.     

Uptake of quercetin and quercetin 3-glucoside from whole onion and apple peel extracts by Caco-2 cell monolayers

Evidence suggests that regular consumption of fruits and vegetables may reduce the risk of chronic diseases, and phytochemicals from fruits and vegetables may be responsible for this health benefit. However, there is limited knowledge on the bioavailability of specific phytochemicals from whole fruits and vegetables. This study used Caco-2 cells to examine uptake of quercetin aglycon and quercetin 3-glucoside as purified compounds and from whole onion and apple peel extracts. Pure quercetin aglycon was absorbed by the Caco-2 cells in higher concentrations than quercetin 3-glucoside (p < 0.05). Caco-2 cells treated with quercetin 3-glucoside accumulated both quercetin 3-glucoside and quercetin. Caco-2 cells absorbed more onion quercetin aglycon than onion quercetin 3-glucoside (p < 0.05), and the percentage of onion quercetin absorbed was greater than that of pure quercetin, most likely due to enzymatic hydrolysis of quercetin 3-glucoside and other quercetin glucosides found in the onion by the Caco-2 cells. Caco-2 cells absorbed low levels of quercetin 3-glucoside from apple peel extracts, but quercetin aglycon absorption was not detected. Caco-2 cell homogenates demonstrated both lactase and glucosidase activities when incubated with lactose and quercetin 3-glucoside, respectively. This use of the Caco2 cell model appears to be a simple and useful system for studying bioavailability of whole food phytochemicals and may be used to assess differences in bioavailability between foods.     

Intestinal absorption of p-coumaric and gallic acids in rats after oral administration

Ferulic acid (FA) and p-coumaric acid (CA) are absorbed by the monocarboxylic acid transporter (MCT) in Caco-2 cells, although gallic acid (GA) is not. Therefore, the MCT is selective for certain phenolic acids. Absorption of orally administered CA and GA in rats was studied to obtain serum pharmacokinetic profiles and to investigate their intestinal absorption characteristics in vivo. Rats were administered 100 micromol/kg body weight of CA and GA, and blood was collected from the portal vein and abdominal artery after administration. CA, GA, and their metabolites were quantified with a highly selective and sensitive coulometric detection method using high-performance liquid chromatography-electrochemical detection. Ingested CA was rapidly absorbed in the gastrointestinal tract in an intact form. The serum concentration of intact CA in the portal vein peaked 10 min after dosing (C(max) was 165.7 micromol/L). In contrast, GA was slowly absorbed, with a t(max) for intact GA of 60 min and a C(max) of 0.71 micromol/L. The area under the curve for intact CA and GA was calculated from the serum concentration profile in the portal vein to be 2991.3 and 42.6 micromol min L(-)(1), respectively. The relative bioavailability of CA against GA was about 70. This is the first demonstration that absorption efficiency of CA is much higher than that of GA in vivo. The absorption characteristics of CA are clearly different from those of GA. These findings are in good agreement with the results obtained in vitro using a Caco-2 cell system.     

The antioxidant and chlorogenic acid profiles of whole coffee fruits are influenced by the extraction procedures

Commercial whole coffee fruit extracts and powder samples were analyzed for chlorogenic acids (CGA), caffeine and antioxidant activities. CGA and caffeine were characterized by LC-MS(n) and HPLC accordingly, and quantified by UV absorbance. ORAC, HORAC, NORAC, SORAC and SOAC (antioxidant capacities) were assessed. Three caffeoylquinic acids, three feruloylquinic acids, three dicaffeoylquinic acids, one p-coumaroylquinic acid, two caffeoylferuloylquinic acids and three putative chlorogenic lactones were quantified, along with a methyl ester of 5-caffeoylquinic acid (detected in one sample, the first such report in any coffee material). Multistep whole coffee fruit extracts displayed higher CGA content than single-step extracts, freeze-dried, or air-dried whole raw fruits. Caffeine in multistep extracts was lower than in the single-step extracts and powders. Antioxidant activity in whole coffee fruit extracts was up to 25-fold higher than in powders dependent upon the radical. Total antioxidant activity of samples displayed strong correlation to CGA content.     

Absorption and bioavailability of artepillin C in rats after oral administration

Artepillin C (AC), an active ingredient of Brazilian propolis, permeates intact across Caco-2 cells by transcellular passive diffusion. The permeation of AC across Caco-2 cells is as efficient as that of phenolic acids and the microbial metabolites of poorly absorbed polyphenols, which are actively absorbed by the monocarboxylic acid transporter (MCT) (Biochim. Biophys. Acta 2005, 1713, 138-144). Here, the absorption of orally administered AC in rats has been studied to evaluate its pharmacokinetics and bioavailability in vivo in comparison with those of p-coumaric acid (CA), a substrate of MCT. Rats were given 100 micromol/kg of body weight of AC or CA, and blood was subsequently collected from the portal vein and abdominal artery. AC, CA, and their metabolites were quantified by coulometric detection using HPLC-ECD. The serum concentration of intact AC and CA in the portal vein peaked at 5-10 min after administration, with a C(max) of 19.7 micromol/L for AC and 74.8 micromol/L for CA. The area under the curve (AUC) for intact AC and CA in the portal vein was calculated from the serum concentration as 182.6 and 3057.3 micromol.min.L(-1), respectively. The absorption efficiency of CA was about 17-fold higher than that of AC. Furthermore, the bioavailability of CA was about 278-fold higher than that of AC, and the ratio of AUC in the abdominal artery to AUC in the portal vein was 0.04 and 0.70, for AC and CA, respectively. Thus, AC is likely to be more susceptible to hepatic elimination than is CA. The bioactive compound of AC in vivo should be investigated further.     

1-MCP负压渗透处理对鲜枣贮藏期间生理及抗氧化能力的影响

以山东大瓜枣为试材,研究1-甲基环丙烯（1-MCP）负压渗透处理对鲜枣贮藏期间生理指标及抗氧化能力的影响。结果表明：1-MCP处理可以维持鲜枣果实体内较低的活性氧水平（H2O2）,提高果实自身抗氧化能力（T-AOC、OH·、O2·-、DPPH）,维持果实自身的抗氧化物质抗坏血酸（AsA）及总酚含量;1-MCP处理对果实过氧化氢酶（CAT）呈现抑制表达作用,而对于抗坏血酸过氧化物酶（APX）、超氧化物歧化酶（SOD）、多酚氧化酶（PPO）和过氧化物酶（POD）则有一定的激活作用。     

Microbial metabolites of ingested caffeic acid are absorbed by the monocarboxylic acid transporter (MCT) in intestinal Caco-2 cell monolayers

It was previously reported that m-coumaric acid, m-hydroxyphenylpropionic acid (mHPP), and 3,4-dihydroxyphenylpropionic acid (DHPP) are major metabolites of ingested caffeic acid formed by gut microflora and would be transported by the monocarboxylic acid transporter (MCT). We have directly measured their absorption characteristics in Caco-2 cells using a coulometric detection method involving HPLC-ECD. The proton-coupled directional transport of m-coumaric acid, mHPP, and DHPP was observed, and the transport was inhibited by an MCT substrate. The permeation of m-coumaric acid and mHPP was concentration-dependent and saturable: The Michaelis constant for m-coumaric acid and mHPP was 32.5 and 12.9 mM, respectively, and the maximum velocity for m-coumaric acid and mHPP was 204.3 and 91.2 nmol (min)(-1) (mg protein)(-1), respectively. By contrast, the permeation of DHPP was nonsaturable even at 30 mM and was inversely correlated with the paracellular permeability of Caco-2 cells. Our results demonstrate that these compounds are absorbed by the MCT, although DHPP is mainly permeated across Caco-2 cells via the paracellular pathway. MCT-mediated absorption of phenolic compounds per se and their colonic metabolites would exert significant impact on human health.     

壳聚糖和抗坏血酸复合处理提高台湾青枣采后保鲜效果

为了延长台湾青枣(Ziziphus mauritiana Lam.)的采后保鲜时间,基于抗坏血酸(ascorbic acid,As A)可提高果实抗氧化能力,壳聚糖涂膜处理能防止果实失水和微生物侵染,该文探讨抗坏血酸、壳聚糖涂膜及抗坏血酸和壳聚糖复合处理对台湾青枣(Ziziphus mauritiana Lam.)采后保鲜效果的影响.果实采收后当天,分别用30.0mmol/L抗坏血酸浸泡处理、8g/L壳聚糖涂膜以及30.0mmol/L抗坏血酸浸泡后并用8g/L壳聚糖涂膜复合处理,以双蒸水浸泡处理为对照,处理结束后,置于(25±1)℃和90%~95%相对湿度下贮藏,定期测定果实相关生理参数,扫描电镜观察果皮果实组织结构.结果表明,与对照相比,抗坏血酸或壳聚糖单独处理虽然对台湾青枣保鲜有一定效果,但复合处理后保鲜效果更好.表现为显著减少果实失水率和相对电导率(P<0.05),抑制果皮叶绿素降解及果实果胶酶和多聚半乳糖醛酸酶活性增加,降低原果胶分解成可溶性果胶的速率(P<0.05),使果实硬度和细胞完整性得以维持;延缓果实超氧化物歧化酶(superoxide dismutase,SOD)和过氧化氢酶(catalase,CAT)活性下降,降低膜脂氧化速率,果实过氧化氢和膜脂过氧化产物丙二醛含量显著下降(P<0.05);维持果实较高的可溶性固形物(total soluble solids,SS)、可溶性总糖(total soluble sugar,TSS)、可滴定酸(titratable acidity,TA)、谷胱甘肽(glutathione,GSH)及抗坏血酸含量.研究结果说明,抗坏血酸和壳聚糖复合处理可提高台湾青枣贮藏过程中的抗氧化能力,降低氧化伤害;降低果实失水率,减缓果皮叶绿素降解速率,延缓细胞降解和软化速率,维持果实细胞完整性,降低果实的腐烂率,从而达到延长采后果实保鲜的效果.