Triterpenoids isolated from apple peels have potent antiproliferative activity and may be partially responsible for apple's anticancer activity

Bioactivity-guided fractionation of apple peels was used to determine the chemical identity of bioactive constituents. Thirteen triterpenoids were isolated, and their chemical structures were identified. Antiproliferative activities of the triterpenoids against human HepG2 liver cancer cells, MCF-7 breast cancer cells, and Caco-2 colon cancer cells were evaluated. Most of the triterpenoids showed high potential anticancer activities against the three human cancer cell lines. Among the compounds isolated, 2alpha-hydroxyursolic acid, 2alpha-hydroxy-3beta-{[(2E)-3-phenyl-1-oxo-2-propenyl]oxy}olean-12-en-28-oic acid, and 3beta-trans-p-coumaroyloxy-2alpha-hydroxyolean-12-en-28-oic acid showed higher antiproliferative activity toward HepG2 cancer cells. Ursolic acid, 2alpha-hydroxyursolic acid, and 3beta-trans-p-coumaroyloxy-2alpha-hydroxyolean-12-en-28-oic acid exhibited higher antiproliferative activity against MCF-7 cancer cells. All triterpenoids tested showed antiproliferative activity against Caco-2 cancer cells, especially 2alpha-hydroxyursolic acid, maslinic acid, 2alpha-hydroxy-3beta-{[(2E)-3-phenyl-1-oxo-2-propenyl]oxy}olean-12-en-28-oic acid, and 3beta-trans-p-coumaroyloxy-2alpha-hydroxyolean-12-en-28-oic acid, which displayed much higher antiproliferative activities. These results showed the triterpenoids isolated from apple peels have potent antiproliferative activity and may be partially responsible for the anticancer activities of whole apples.     

基于流变特性的不同品种苹果果皮质地评价

为探究苹果果皮表面碎裂损伤的原因和评价不同品种果皮的质地。采用电子万能试验机对丹霞、红富士和新红星苹果果皮进行拉伸松弛和蠕变特性试验,得到了果皮松弛的初始应力、残余应力、应变保持和蠕变的初始应变、应力保持、蠕变量;建立了苹果果皮松弛和蠕变的数学模型,对松弛和蠕变特性参数进行了相关性和主成分分析。结果表明:松弛和蠕变试验结果揭示出不同品种果皮的流变特性和内部组织结构存在差异。不同品种果皮的初始应力较大时,松弛平衡后的残余应力较大;初始应变较大时,蠕变量较小。新红星果皮的弹性因子贡献率较高,而红富士果皮的黏性因子贡献率较高,反映出红富士果皮表面中较新红星和丹霞果皮表面容易碎裂损伤,在采收、运输等过程中红富士的果皮较新红星和丹霞的果皮易受机械损伤。研究结果可为苹果品种的优育及其质地评价体系的建立和完善提供参考。     

Phytochemicals of apple peels: isolation, structure elucidation, and their antiproliferative and antioxidant activities

Bioactivity-guided fractionation of Red Delicious apple peels was used to determine the chemical identity of bioactive constituents, which showed potent antiproliferative and antioxidant activities. Twenty-nine compounds, including triterpenoids, flavonoids, organic acids and plant sterols, were isolated using gradient solvent fractionation, Diaion HP-20, silica gel, and ODS columns, and preparative HPLC. Their chemical structures were identified using HR-MS and 1D and 2D NMR. Antiproliferative activities of isolated pure compounds against HepG2 human liver cancer cells and MCF-7 human breast cancer cells were evaluated. On the basis of the yields of isolated flavonoids (compounds 18- 23), the major flavonoids in apple peels are quercetin-3-O-beta-D-glucopyranoside (compound 20, 82.6%), then quercetin-3-O-beta-D-galactopyranoside (compound 19, 17.1%), followed by trace amounts of quercetin (compound 18, 0.2%), (-)-catechin (compound 22), (-)-epicatechin (compound 23), and quercetin-3-O-alpha-L-arabinofuranoside (compound 21). Among the compounds isolated, quercetin (18) and quercetin-3-O-beta-D-glucopyranoside (20) showed potent antiproliferative activities against HepG2 and MCF-7 cells, with EC 50 values of 40.9 +/- 1.1 and 49.2 +/- 4.9 microM to HepG2 cells and 137.5 +/- 2.6 and 23.9 +/- 3.9 microM to MCF-7 cells, respectively. Six flavonoids (18-23) and three phenolic compounds (10, 11, and 14) showed potent antioxidant activities. Caffeic acid (10), quercetin (18), and quercetin-3-O-beta-D-arabinofuranoside (21) showed higher antioxidant activity, with EC 50 values of <10 microM. Most tested flavonoids and phenolic compounds had high antioxidant activity when compared to ascorbic acid and might be responsible for the antioxidant activities of apples. These results showed apple peel phytochemicals have potent antioxidant and antiproliferative activities.     

Antioxidant activity of grains

Epidemiological studies have shown that consumption of whole grains and grain-based products is associated with reduced risk of chronic diseases. The health benefits of whole grains are attributed in part to their unique phytochemical composition. However, the phytochemical contents in grains have been commonly underestimated in the literature, because bound phytochemicals were not included. This study was designed to investigate the complete phytochemical profiles in free, soluble conjugated, and insoluble bound forms, as well as their antioxidant activities in uncooked whole grains. Corn had the highest total phenolic content (15.55 +/- 0.60 micromol of gallic acid equiv/g of grain) of the grains tested, followed by wheat (7.99 +/- 0.39 micromol of gallic acid equiv/g of grain), oats (6.53 +/- 0.19 micromol of gallic acid equiv/g of grain), and rice (5.56 +/- 0.17 micromol of gallic acid equiv/g of grain). The major portion of phenolics in grains existed in the bound form (85% in corn, 75% in oats and wheat, and 62% in rice), although free phenolics were frequently reported in the literature. Ferulic acid was the major phenolic compound in grains tested, with free, soluble-conjugated, and bound ferulic acids present in the ratio 0.1:1:100. Corn had the highest total antioxidant activity (181.42 +/- 0.86 micromol of vitamin C equiv/g of grain), followed by wheat (76.70 +/- 1.38 micromol of vitamin C equiv/g of grain), oats (74.67 +/- 1.49 micromol of vitamin C equiv/g of grain), and rice (55.77 +/- 1.62 micromol of vitamin C equiv/g of grain). Bound phytochemicals were the major contributors to the total antioxidant activity: 90% in wheat, 87% in corn, 71% in rice, and 58% in oats. Bound phytochemicals could survive stomach and intestinal digestion to reach the colon. This may partly explain the mechanism of grain consumption in the prevention of colon cancer, other digestive cancers, breast cancer, and prostate cancer, which is supported by epidemiological studies.     

Antioxidant activity of capsinoids

Hot peppers are a good source of dietary antioxidants, encompassing, apart from widespread compounds (flavonoids, phenolic acids, carotenoids, vitamin A, ascorbic acid, tocopherols), also specific constituents such as the pungent capsaicinoids (capsaicin, dihydrocapsaicin, and related analogues). We have shown that capsinoids also show remarkable antioxidant activity. These benign analogues of capsaicin could protect linoleic acid against free radical attack in simple in vitro systems, inhibiting both its autoxidation and its iron- or EDTA-mediated oxidation. These properties were retained in some simple synthetic analogues (vanillyl nonanoate and its dimerization products). Capsiate, dihydrocapsiate, and their analogues were devoid of pro-oxidant activity and showed a highly significant antioxidant activity in all systems investigated. Vanillyl nonanoate, a simple capsinoid mimic, was also tested on cell cultures for cytotoxic activity and the capacity to inhibit FeCl(3)-induced oxidation.     

Antioxidant activity of dodecyl gallate

Dodecyl (C12) gallate exhibits both potent chain-breaking and preventive antioxidant activity. The pyrogallol moiety is responsible for both activities. Dodecyl (lauryl) gallate prevents generation of superoxide radicals by xanthine oxidase, and this activity comes from its ability to inhibit the enzyme. The inhibition kinetics analyzed by Lineweaver-Burk plots found that dodecylgallate is a noncompetitive inhibitor for the generation of superoxide anion. Dodecyl gallate also inhibits formation of uric acid. The inhibition kinetics analyzed by Lineweaver-Burk plots found that dodecyl gallate is a competitive inhibitor for this oxidation. Mitochondrial lipid peroxidation induced by Fe(III)-adenosine 5'-diphosphate/reduced nicotinamide adenine dinucleotide was inhibited by dodecyl gallate while its parent compound, gallic acid, did not show this inhibitory activity. Dodecyl gallate protected mitochondrial functions and human red blood cells against oxidative stresses, but gallic acid showed little effect. The hydrophobic dodecyl group is largely associated with the preventive antioxidative activity.     

Antioxidant activity of Glossogyne tenuifolia

Glossogyne tenuifolia is a native traditional anti-inflammatory herb in Taiwan. It has previously been shown that the ethanol extract of G. tenuifolia (GT) inhibited the LPS-induced inflammatory mediator release from murine macrophage cell line and human whole blood. In the present work, the ethanol extracts of G. tenuifolia and its major constituent, luteolin-7-glucoside, were shown to be scavengers of 1,1-diphenyl-2-picrylhydrazyl, superoxide, and hydroxyl radicals. Moreover, copper-induced low-density lipoprotein oxidation was suppressed by GT and luteolin-7-glucoside as measured by decreased formation of malondialdehyde and conjugated diene as well as reduced electrophoretic mobility. GT and luteolin-7-glucoside were also against N-formyl-methionyl-leucyl-phenylalanine-induced reactive oxygen species (ROS) production in human polymorphonuclear neutrophils and peripheral blood mononuclear cells. In summary, these data indicated that GT is a potential ROS scavenger and may prevent atherosclerosis via inhibiting LDL oxidation or ROS production in human leukocytes. Moreover, luteolin-7-glucoside may serve as the active principal of GT.     

Antioxidant activity of protein-bound quercetin

Bovine serum albumin (BSA) was derivatized by covalent attachment of different amounts of quercetin [ratios of BSA to quercetin were 20:1, 10:1, 7:1, 5:1, and 2:1 (w/w)]. The antioxidant activity of the protein-phenol derivatives was investigated using a modified TEAC assay. The results show that the covalent attachment of quercetin to BSA decreases the total antioxidant activity in comparison to an equivalent amount of free quercetin depending on the degree of derivatization. The derivative with the highest amount of covalently bound quercetin (the 2:1 derivative) showed an antioxidant activity of only 79% compared to an equivalent amount of free quercetin. After the enzymatic proteolysis of the BSA-quercetin derivatives with trypsin, the total antioxidant activity of the degradation products increases in comparison to the respective undigested derivatives but does not reach the activity of an equivalent amount of free quercetin. Even after 240 min of tryptic degradation, there is still a lack in antioxidant activity (for the 7:1 derivative nearly 33%) as compared to free quercetin.     

Antiangiogenic activity of nasunin, an antioxidant anthocyanin, in eggplant peels

Nasunin, delphinidin-3-(p-coumaroylrutinoside)-5-glucoside, an antioxidant anthocyanin isolated from eggplant peels, was demonstrated as an angiogenesis inhibitor. Nasunin at higher 10 microM suppressed microvessel outgrowth in an ex vivo angiogenesis assay using a rat aortic ring. The effect of nasunin was examined in various in vitro angiogenesis models using human umbilical vein endothelial cells (HUVECs). Nasunin suppressed HUVEC proliferation in a dose-dependent manner (50-200 microM); however, it had no significant effect on HUVEC chemotaxis in a Boyden chamber assay and HUVEC tube formation on a reconstituted basement membrane. These results imply that nasunin with both antioxidant and antiangiogenic activities might be useful to prevent angiogenesis-related diseases.     

Effect of heat treatment on the antioxidant activity of extracts from citrus peels

The effect of heat treatment on the antioxidant activity of extracts from Citrus unshiu peels was evaluated. Citrus peels (CP) (5 g) were placed in Pyrex Petri dishes (8.0 cm diameter) and heat-treated at 50, 100, or 150 degrees C for 10, 20, 30, 40, 50, and 60 min in an electric muffle furnace. After heat treatment, 70% ethanol extract (EE) and water extract (WE) (0.1 g/10 mL) of CP were prepared, and total phenol contents (TPC), radical scavenging activity (RSA), and reducing power of the extracts were determined. The antioxidant activities of CP extracts increased as heating temperature increased. For example, heat treatment of CP at 150 degrees C for 60 min increased the TPC, RSA, and reducing power of EE from 71.8 to 171.0 microM, from 29.64 to 64.25%, and from 0.45 to 0.82, respectively, compared to non-heat-treated control. In the case of WE from CP heat-treated at the same conditions (150 degrees C for 60 min), the TPC, RSA, and reducing power also increased from 84.4 to 204.9 microM, from 15.81 to 58.26%, and from 0.27 to 0.96, respectively. Several low molecular weight phenolic compounds such as 2,3-diacetyl-1-phenylnaphthalene, ferulic acid, p-hydroxybenzaldoxime, 5-hydroxyvaleric acid, 2,3-diacetyl-1-phenylnaphthalene, and vanillic acid were newly formed in the CP heated at 150 degrees C for 30 min. These results indicated that the antioxidant activity of CP extracts was significantly affected by heating temperature and duration of treatment on CP and that the heating process can be used as a tool for increasing the antioxidant activity of CP.     

Antioxidant activity of indigenous edible mushrooms

The current study was undertaken to measure the antioxidant potential from water and methanolic extracts of fruiting bodies of 23 species of mushrooms naturally grown in different geographic locations of India. The antioxidant ability of each species was analyzed for the total antioxidative status, employing multimechanistic antioxidative assays such as inhibition of lipid peroxidation, determination of reducing power, and free radical scavenging ability, in addition to determination of total phenolics and identification of phenolic acids by HPLC analysis, because the phenolics are known to contribute largely to antioxidant potential. The antioxidant potential of these varieties of mushrooms was determined by summing the antioxidative activity (AOA) of each variety by varied antioxidant assays followed by determining the relative percent of AOA defined as the "antioxidant index" (AI). On the basis of the AI, the mushroom species were graded as very high, high, moderate, and low. Termitomyces heimii was identified as the best variety, which showed 100% AI with 37 mg of phenolics/g of sample, 418 units of reducing power ability (RPA)/g, and an IC50 of approximately 1.1 mg (dry weight)/mL, free radical scavenging activity (FRS) in the water extract followed by 11.2 mg of phenolics/g, 275 units of RPA/g, and an IC50 of approximately 2.7 mg (dry weight)/mL of FRS in the methanolic extract. Following T. heimii, Termitomyces mummiformis exhibited an AI of 86% within the "very high" group. Potent inhibitions of lipid peroxidation of approximately 100 and 69% was also observed in T. heimii and T. mummiformis, respectively. Water extracts ranged from 34 to 49% and methanolic extracts varied from 20 to 32% on dry weight of mushroom fruiting body. Total phenolic compounds were higher in the water extracts (2-37 mg/g) than in methanolic extract (0.7-11.2 mg/g). The AOA measured in the water extract was better than that from the methanolic extract. HPLC analysis of phenolic acids in the two mushroom species, namely, T. heimii and T. mummiformis, displaying maximum AOA potential indicated a preponderance of tannic acid, gallic acid, protocatacheuic acid, and gentisic acid. Studies thus provide the precise antioxidant status of 23 indigenous species of mushrooms, which can serve as a useful database for the selection of mushrooms for the function of preparation of mushroom-based nutraceutics.     

Antioxidant activity of fermented soybean extract

Free radicals are considered to be important causative factors in the development of cancer and cardiovascular diseases. This relationship has led to interest in evaluating the antioxidant capacities of many dietary supplements. Fermented soybean extract is produced by symbiotic fermentation of organic soybean with 20 types of Lactobacillus and yeast. In vitro and in vivo models are used in this study to evaluate the antioxidant effect of fermented soybean extract. Several in vitro models are used to detect the antioxidant capacity of the fermented soybean extract, which is compared to vitamin C and Trolox. The results demonstrate that the fermented soybean extract has strong antioxidant activity against unsaturated fatty acid peroxidation compared to vitamin C and Trolox. By the means of the test system developed by Y. Toshiki et al., it is shown that the fermented soybean extract can function both as an antioxidant and as a free radical acceptor that can convert free radicals into harmless substances through an energy-decreasing procedure. An in vivo study examines the effects of fermented soybean extract on the activity of antioxidant enzymes. The activities of the antioxidant enzymes (AOE) including total superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) are measured in liver, kidney, and brain from male Sprague-Dawley rats. The activities of CAT, SOD, and GPX are increased in the liver. However, the SOD activity is decreased in the kidney. SOD and GPX activities are decreased in the brain. These results lead to the conclusion that fermented soybean extract not only has antioxidant activity but also has an effect on the activity of antioxidant enzymes in liver.     

Antioxidant activity of coffee model systems

Coffee model systems prepared from combinations of chlorogenic acid (CGA), N(alpha)-acetyl-1-arginine (A), sucrose (S), and cellulose (C) were roasted at 240 degrees C for 4 min prior to analysis by UV-visible spectrophotometry, capillary zone electrophoresis (CZE), and the ABTS radical cation decolorization assay. The A/CGA/S/C and A/S/C systems were also fractionated by gel filtration chromatography. Antioxidant activity of the systems showed a positive, nonlinear relationship with the amount of CGA remaining after roasting. Sucrose degradation was a major source of color in the heated systems. There was no relationship between antioxidant activity and color generation.     

Antioxidant activity of malt rootlet extracts

To improve the malt rootlet value, the antioxidant potentialities of this byproduct of the malting industry have been analyzed. Three extracts have been considered from the points of view of dry matter yield, level of antioxidant compounds, and efficiency and cost of the extraction protocols. They respectively contain rootlet oil, free phenolic compounds, and bound phenolic compounds. The rootlet oil contains only a low quantity of tocopherols (respectively, 20.6 and 4.2 microgram of alpha-tocopherol and gamma-tocopherol per gram of dry rootlets), and a weak antioxidant activity, evaluated in a stripped corn oil by following spectrophotometrically the conjugated dienes, has been pointed out. The bound compound extract presents a good antioxidant power mainly due to the presence of trans-ferulic and trans-p-coumaric acids, but the dry matter yield is low (2%). The free compound extract has a good antioxidant power, and the valuable dry matter, mainly composed of proteins (52%), sugars (33%), and reducing compounds (5.5%), has a yield of 12%. The mixing of bound and free compound extracts presents an antagonistic effect on the antioxidant power, but a synergistic effect has been pointed out for the mixing of alpha-tocopherol and free compound extract.     

Antioxidant activity of capsaicinoid in canola oil

Interest in replacing synthetic antioxidants, namely, butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA), with natural antioxidants is increasing. The present study examined the antioxidant activity of capsaicinoid from chili pepper in heated canola oil. The oxidation was conducted at 60, 90, 120, and 180 °C by monitoring oxygen consumption and the decrease in linoleic acid and α-linolenic acid in canola oil. At 60 °C, capsaicinoid was more effective against oxidation of canola oil compared with BHT. At higher temperatures of 90, 120, and 180 °C, capsaicinoid possessed an antioxidant activity similar to or slightly weaker that that of BHT. It was found that capsaicinoid prevented canola oil from oxidation in a dose-dependent manner. To study the structure-antioxidant relationship, it was found that the trimethylsiloxy (TMS) derivatives of capsaicinoid did not exhibit any antioxidant activity, suggesting the hydroxyl moiety was the functional group responsible for the antioxidant activity of capsaicinoid. It was concluded that capsaicinoid had the potential to be further explored as a natural antioxidant in foods, particularly spicy foods.     

Antioxidant activity of anthocyanins and their aglycons

The antioxidant activity of the six common anthocyanidins, pelargonidin, cyanidin, delphinidin, peonidin, petunidin, and malvidin, and their glycosidic forms was evaluated in three lipid-containing models [human low-density lipoprotein (LDL) and bulk and emulsified methyl linoleate]. In addition, the radical scavenging activity of the compounds against the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical was studied. Most anthocyanins and their aglycons acted as strong antioxidants in emulsion and LDL. Many compounds showed an activity comparable to the well-known antioxidants alpha-tocopherol, Trolox, catechin, and quercetin. In bulk methyl linoleate, anthocyanins and anthocyanidins possessed only a weak antioxidant activity or even oxidation-promoting activity. Depending on the anthocyanidin, different glycosylation patterns either enhanced or diminished the antioxidant power. For the most part, the activities of the glycosides and the aglycons did not differ remarkably in emulsion. In LDL the aglycons showed in general higher activities than the glycosides. In bulk oil, to the contrary, the glycosides were more effective than the aglycons.     

Antioxidant and antiulcerative properties of phenolics from Chinese quince, quince, and apple fruits

To evaluate the health benefits of Chinese quince and quince phenolics, their antioxidant properties and antiulcerative activity were investigated in comparison with apple phenolics as a reference. The strength of antioxidant activity and DPPH radical scavenging activity of these fruit phenolics varied according to different in vitro evaluation systems, whereas the antioxidative property of rat blood increased in all rats orally administered phenolics. Ferulic acid and isoferulic acid were detected as major metabolites in rats given apple phenolics, quince phenolics, and 5-caffeoylquinic acid standard. (-)-Epicatechin and its 3'-O-methyl ether could be detected in rats administered apple phenolics and (-)-epicatechin standard. In the ethanol-induced gastric ulcer, pre-administration of Chinese quince and quince phenolics suppressed the occurrence of gastric lesions in rats, whereas apple phenolics seemed to promote ulceration. The trend of myeloperoxidase activity was similar to that of the ulcer index. The results showed that Chinese quince and quince phenolics might have health benefits by acting both in blood vessels and on the gastrointestinal tract.     

Peroxidase activity and superficial scald development in apple fruit

The relationship between soluble peroxidase (EC 1.11.1.7; POX) activity and the development of a chilling-related disorder, superficial scald, was studied in three apple fruit (Malus x domestica Borkh.) systems: a White Angel x Rome Beauty population with progeny with different scald susceptibilities; Delicious from three harvests with progressively declining scald susceptibility; and the scald-resistant Idared and the scald-susceptible Law Rome. Differences in incidence and severity of scald in progeny from White Angel x Rome Beauty progeny tended to show relationships with POX activity at harvest, but, overall, associations were not consistent. However, greater scald incidence and lower POX activity were found in less mature Delicious fruit than in later harvested fruit. Also, the scald-resistant Iotadared had a much higher POX activity compared with the scald-susceptible Law Rome. A general hypothesis that POX activity is related to scald susceptibility was generally supported, but exceptions were observed.     

Antioxidant activity and phenolic content of Oregon caneberries

Five types of caneberries [evergreen blackberries (Rubus laciniatus), marionberries (Rubus ursinus), boysenberries (Rubus ursinus x idaeus), red raspberries (Rubus idaeus), and black raspberries (Rubus occidentalis)] were analyzed for antioxidant activity by measuring their oxygen radical absorbance capacity (ORAC). In addition, the berries were analyzed for total phenolics, anthocyanins, procyanidins, and ellagic acid content. All of the berries had high ORAC activity ranging from 24 to 77.2 micromol of Trolox equiv/g of fresh berries. Anthocyanin content ranged from 0.65 to 5.89 mg/g, and phenolics ranged from 4.95 to 9.8 mg/g. Black raspberries had the highest ORAC and anthocyanin and phenolic contents. Only red raspberries had detectable amounts of procyanidin oligomers (monomer, dimers, and trimers). All berries had high levels of ellagic acid (47-90 mg/g), but boysenberries had the highest level prior to hydrolysis. The results from this study indicate that these caneberries were high in antioxidant activity and were rich sources of anthocyanins and phenolics.     

Antioxidant activity of Sempervivum tectorum and its components

The antioxidant properties of components of leaf extracts of the evergreen plant, Sempervivum tectorum (ST), have been evaluated using UV irradiated liposomal systems containing the spin trap 5-(diethoxyphosphoryl)-5-methyl-pyrroline-N-oxide. Decreases in free radical activity in the liposomal systems as measured by electron paramagnetic resonance (EPR) spectroscopy demonstrate that the lipophilic ST juice components, kaempferol (KA) and kaempferol-3-glucoside (KG) contribute significantly to the antioxidant properties of the juice. EPR spectral simulation established the presence of oxygen and carbon centered free radical adducts. The mixtures with low pH, citric and malic acid, and ST juice reveal increased EPR signals from oxygen centered radicals in comparison to the control, pointing to the important role of pH in oxygen radical formation. Parallel assays that measured thiobarbituric acid related substances confirm the antioxidant effects of KA and KG and explain the results of spin trapping experiments complicated by low pH's.