Fatty acids,tocopherols, phenolic and antioxidant properties of six citrus fruit species: a comparative study

Citrus fruit is a rich source of bioactive phytochemicals. Information on the fatty acid and tocopherol composition of locally grown citrus fruits in Korea is elusive. This work was aimed to study fatty acid, tocopherols, ascorbic acid, antioxidant potential, and selected phenolics from peel and pulp of six citrus species. The most dominant fatty acid was linoleic acid (15–45%), followed by linolenic, palmitic, and oleic acid. Stearic acid was highly abundant in yuzu peel (14.45%) and pulp (15.88%) compared to the other fruits. Unsaturated fatty acids (54–74%) contributed higher composition than saturated fatty acids (25–46%). Peel exhibited better antioxidant potential and contained higher phytochemicals than pulp. The concentrations of α-tocopherol and γ-tocopherol were ranged from 22.96 (yuzu) to 86.93 (cheonhyeyang) and 38.59 (yuzu) ~83.03 (tangerine) μg/g DW, respectively. J-Redhyeyang peel exhibited highest total flavonoids (4.17?±?0.10 mgQE/g DW) and DPPH radical scavenging activity (6.17?±?0.03 mgTE/g DW). FRAP values were highest (20.05?±?0.64 mgTE/g DW) in yuzu peel, while peel of cheonhyeyang was superior in total phenolic contents. Tangerine (3.02?±?0.05 mg/g DW) and yuzu (7.49?±?0.38 mg/g DW) had higher hesperidin concentrations in pulp and peel, respectively. Naringin was found in an appreciable amount in yuzu pulp (2.04?±?0.09 mg/g DW) and peel (6.30?±?0.19 mg/g DW) but not detected in all other fruit species. Our results indicate that citrus fruit peel is the rich source of antioxidant compounds, which can be used to prepare antioxidant rich food product.     

HPLC测定番荔枝果实中酚类成分及抗氧化相关性

目的：建立高效液相色谱（high performance liquid chromatography,HPLC）法同时测定番荔枝果实3 个部位中13 种酚类成分的种类及含量,并分析含量与抗氧化活性的相关性。方法：采用福林-酚法测定总酚含量;通过HPLC法对番荔枝果实中的单酚成分进行比较;通过1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）自由基与2,2’-联氮双(3-乙基苯并噻唑啉-6-磺酸)（2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid),ABTS）阳离子自由基清除能力的检测方法测定番荔枝果实的抗氧化活性。结果：番荔枝果实中总酚含量为果皮＞果肉＞种子,果皮含量最高为59.48～127.84 mg/g;番荔枝单酚含量结果表明果皮显著高于果肉和种子部位,各产地酚类种类和含量差异显著。果皮和果肉中对羟基苯甲酸、儿茶素、咖啡酸、表儿茶素含量相对较高,表儿茶素最高为2 398.17 mg/mL。抗氧化结果表明番荔枝果实清除ABTS阳离子自由基能力高于DPPH自由基,且果皮活性最好,分别在质量浓度为0.39、1.56 mg/mL时均达到最高清除率。结论：番荔枝果实中果皮、果肉、种子3 个部位中所含酚类物质种类及含量有显著性差异;果皮部位所含种类及含量均最高,且抗氧化活性最佳,可作为天然抗氧化剂。     

Potential dietary sources of ellagic acid and other antioxidants among fruits consumed in Brazil: jabuticaba (Myrciaria jaboticaba (Vell.) Berg)

BACKGROUND: The objectives of this study were (1) to evaluate the content of ellagic acid in fruits consumed by the Brazilian population, including native ones; (2) to further characterize rich sources in relation to ascorbic acid, phenolics contents and in vitro antioxidant capacity; and (3) to study the distribution and effect of ripening stage on ellagitannins content of jabuticaba (Myrciaria jaboticaba). The content of free ellagic acid and ellagic acid derivatives such as ellagitannins was analyzed using high‐performance liquid chromatography (HPLC). RESULTS: Ellagic acid was detected in 10 out of a total of 35 fruits analyzed. The content of free ellagic acid in fruits varied from 0.0028 to 0.085 g kg^?1 (FW) and total ellagic acid varied from 0.215 to 3.11 g kg^?1 (FW). All the seven fruits belonging to the Myrtaceae family evaluated in this study presented high contents of ellagitannins in their composition, with jabuticaba, grumixama and cambuci (all native from Brazil) showing the highest total ellagic acid contents. Jabuticaba, the most consumed in Brazil among those and already adapted to commercial plantations, contained concentrated phenolics compounds, including ellagitannins, in the peel. Anthocyanins (cyanidin derivatives) increased significantly through ripening of jabuticaba and were not present in the pulp or seeds. Samples collected from three different locations during summer, winter and spring had total ellagic contents varying from 1.88 to 3.31 g kg^?1 (FW). The decrease in ellagic acid content with ripening was more accentuated for pulp (eight times) compared to seeds (2.3 times) and peel (2.0 times). CONCLUSION: These results showed the potential of jabuticaba as dietary source of ellagic acid and reinforced consumption of the whole fruit by the population. Copyright © 2011 Society of Chemical Industry     

菝葜果实主要成分及氨基酸含量分析

对菝葜(Smilax china L.)果实不同部位的主要成分及氨基酸含量进行分析。结果表明：与种子、果皮相比,菝葜果肉的含水量、还原糖含量、总糖含量均最高,果肉的总酸含量与种子接近,色素物质主要集中在果皮内。种子的蛋白质、脂肪及淀粉含量均最高,果皮的蛋白质含量最低,果肉的淀粉含量最低。果肉和种子均含有 17 种氨基酸,其中包括7 种人体必需氨基酸,除了苏氨酸和亮氨酸外,其余几种必需氨基酸的比例均超过或接近WHO/FAO 标准模式。因此,菝葜果实具有较高的食用价值,还可以进行精深加工。     

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.     

Evaluation of the Antioxidant Properties of the Brazilian Cerrado Fruit Annona crassiflora (Araticum)

Annona crassiflora, known commonly as araticum, is an exotic tropical fruit consumed mainly by native people of the Brazilian Cerrado (2nd biggest biome of Brazil). In this study, pulp, seed, and peel of slight ripe and overripe fruits were extracted using ethanol and water. The extracts showed high content of total phenols and were screening for their potential as antioxidants using the in vitro model 1,1‐ dipheniyl‐2‐picryl hydrazyl (DPPH). The ethanol extracts of peel and seeds showed IC50 of 48.82 μg/mL and 31.14 μg/mL, respectively, for the slightly ripe fruits. As the ethanolic fractions of araticum showed the highest antioxidant activity, they were selected for testing of its effect on lipid peroxidation. The ethanolic extracts of slightly ripe fruits showed IC₅₀ of 4.44 μg/mL, 1.72 μg/mL, and 8.62 μg/mL for the peel, seed, and pulp, respectively. This is the 1st report on the antioxidant properties of the extracts of araticum. Owing to these properties, the studies can be further extending to exploit them for their possible application as natural antioxidant for cosmetic, supplements, and functional ingredients for food products.     

ANTIOXIDANT ACTIVITY AND TOTAL PHENOLIC CONTENTS IN PEEL AND PULP OF CHINESE JUJUBE (ZIZIPHUS JUJUBA MILL) FRUITS

Total phenolic contents in peel and pulp of the fruits of three Chinese jujube cultivars ( Ziziphus jujuba cv. mayazao, Z. jujuba cv. dongzao and Z. jujuba cv. yuanzao) were determined. The antioxidant activities in peel and pulp of the jujube fruits were measured by different methods, including 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity, ferric reducing antioxidant power (FRAP) and Trolox equivalent antioxidant capacity (TEAC). The total phenolic content in peel was five to six times higher than that in the pulp of all the three cultivars. The phenolics contents in the jujube were different with cultivars. The EC₅₀ ( Concentration of lyophilized samples needed to decrease the initial DPPH radical concentration by 50% ), FRAP and TEAC values of the peel and pulp were remarkably correlated to their total phenolic contents (R  = − 0.922, R  =  0.985 and R  =  0.997, respectively). The results indicated that the high capacity of antioxidant of Chinese jujube fruit could be attributed to the high phenolic contents in the fruit.

PRACTICAL APPLICATIONS

There was an expanding quest surrounding the use of antioxidant because they have the capacity to protect from the damage because of free radicals and reactive oxygen species. However, the safety of synthetic antioxidant was challenged. Much attention has been focused on the use of natural antioxidant. Interest in food phenolics had increased greatly because of their antioxidant and possible promoting-health role in human health. In this study, total phenolic contents and antioxidant capacities in vitro of Chinese jujube ( Ziziphus jujuba Mill) peel and pulp were researched. The work would help to explore a natural antioxidant for possible application in food and dietary supplemental products for health promotion.     

Pilosocereus arrabidae (Byles & Rowley) of the Grumari sandbank,RJ, Brazil: Physical,chemical characterizations and antioxidant activities correlated to detection of flavonoids

The fruits of Pilosocereus arrabidae (Cactaceae) is found in the Grumari shoal, located in the Rio de Janeiro state, Brazil and, several studies have already highlighted the importance of consuming its fruits. This work aims to investigate the physical, mineral and physicochemical properties of its fruits as well as to establish the knowledge about their chemical constituents and antioxidant properties. The peel (Pe) and pulp (Pu) extracts were obtained by maceration with the following solvents: hexane (HX), dichloromethane (DCL), ethyl acetate (EAC) and ethanol 70% (ET). The extracts were analyzed by Gas Chromatography coupled to Mass Spectrometry (GC–MS) and, by High Performance Liquid Chromatography (HPLC–DAD and HPLC–MS) for its chemical investigation. For the antioxidant activity investigations the ORAC, DPPH and ferrous ion chelating capacity (FICC) tests were performed. As results, we found higher yields for peels (72%) compared to pulps (28%). By the physical–chemical analyses we point out the fruits as a good source of fiber (pulp: 6.01 mg/100 g; peel: 8.02 mg/100 g). The minerals were analyzed by the method of issuing flames and indicated high levels of selenium (DRI for pulp and peel: 147%) and manganese (DRI pulp: 97.69% and DRI peel: 269.56%). The total flavonoid contents of the fruits performed by HPLC–DAD presented 0.45 μg equiv. in quercetin/mL of peel EAC extract and 0.25 μg equiv. in rutin/mL of pulp EAC extract. The antioxidant activities by the ORAC, FICC and DPPH methods indicated that the ET extracts showed antioxidant activities above the standards adopted for the tests. Among these, we highlight the ET extract of the pulp with EC₅₀ of 17.57 ± 0.27 μg/mL, lower than Ginkgo biloba EGB761® (23.40 ± 0.04 mg/mL). By the FICC test the EAC extract of the peel and pulp showed 70.0% and 53.4% activity, respectively, at 500 mg/mL, higher than the standard quercetin (50.0%). By the HPLC–DAD and HPLC–MS methods there were detected, for the first time on this species, the presence of the following flavonoids on the EAC extracts: quercetin, rutin, catechin, dihydrokaempferol, quercetin 3 or 4′-O-glucoside, kaempferol and isorhamnetin. By the GC–MS analysis there were detected on the DCL extracts saturated fatty acids (palmitic and stearic) and, on the HX extracts, methylated sugars (peel) and menthol (pulp). To sum up, the fruits of P. arrabidae display antioxidant potential correlated to flavonoid presence, and, high levels of selenium, manganese and fibers, characteristics that can promote beneficial effects on human health.     

毛叶山桐子果实化学成分及脂肪酸动态分析与评价

对不同生长期的重庆1号、重庆2号品种的毛叶山桐子果实的整果、果肉和种子中的基本化学成分含量进行比较,并运用气相色谱法对油脂中脂肪酸组成及相对含量进行分析.结果表明,2个品种果实在不同生长期和不同部位中粗脂肪、蛋白质、总糖、灰分、总酚、总黄酮等成分含量差异显著(P＜0.05);2个品种毛叶山桐子作为油脂原料的最佳采收期分...     

Antioxidant Activity of Loquat (Eriobotrya japonica Lindl.) Fruit Peel and Pulp Extracts in Stabilization of Soybean Oil During Storage Conditions

The antioxidation activities of Eriobotrya japonica (Lindl.) fruit peel and pulp extracts were determined using DPPH, β-carotene, and Rancimat methods. Results showed that ethanol-water extract of peel and ethanol extract of pulp had the highest antioxidant activity. Protective effects of extracts in stabilization of soybean oil were tested and compared to tert-butyl hydroquinone by measuring peroxide values, free fatty acids, thiobarbituric acid, oxidative stability, and conjugated dienes and trienes values during storage (65 days at 25°C). Results showed that the ethanol-water extract of peel at 400 ppm exhibited stronger antioxidant activity, but the highest effect was observed in tert-butyl hydroquinone.     

Identification and quantification of phenolic and other polar compounds in the edible part of Annona cherimola and its by-products by HPLC-DAD-ESI-QTOF-MS

Annona cherimola fruit is native to inter-Andean valleys from Peru and Ecuador. In the Mediterranean region, the main producer of cherimoya is the coast of Granada–Malaga (Spain), also called ‘Costa Tropical’, where the two most important cultivars found are ‘Fino de Jete’ and ‘Campa’.Cherimoya, like most fruits, is an important source of bioactive compounds, such as phenolic compounds. Therefore, the aim of this study was the tentative identification and quantification of phenolic and organic acids in pulp, peel and seed of two cherimoya cultivars (‘Fino de Jete’ and ‘Campa’) using HPLC-DAD-ESI-QTOF-MS.By using the proposed method, 21 phenolic and organic acids were detected in the edible portion of cherimoya, 37 in peel and 22 in seed. Procyanidins were the main phenolic compound family identified in the pulp and peel of the two cultivars, whereas in cherimoya seeds higher quantities of organic acids and flavonoids were detected. Most of the compounds were identified for the first time in cherimoya.According to these results, cherimoya pulp and its by-products are a natural source of procyanidins and other phenolic and polar compounds. In particular, cherimoya peel, with a higher concentration of phenolic and polar compounds in comparison with pulp and seed, represents an interesting food by-product that could be used as an ingredient in the functional food and/or pharmaceutical industry.     

8 种猕猴桃不同组织部位的体外抗氧化活性

为了探明猕猴桃不同组织部位的抗氧化活性,进而提高猕猴桃多层次的综合开发利用,该研究测定了8 个品种猕猴桃全果（可食用部分）的理化指标与1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）自由基、羟自由基（·OH）、2,2’-联氮-二（3-乙基-苯并噻唑-6-磺酸）二铵盐（2,2’-amino-di(3-ethyl-benzothiazoline-6-sulphonic acid)ammonium salt,ABTS）自由基清除能力和Cu2＋、Fe3＋还原力等体外抗氧化指标,并对理化指标和抗氧化指标进行了相关性分析,同时分别探究了猕猴桃果皮、果肉、果心的抗氧化活性成分含量以及对全果体外抗氧化活性的贡献率。结果表明：8 个猕猴桃品种,华优的体外抗氧化活性最强,海沃德最弱。进行相关性检验,猕猴桃中起抗氧化作用的成分主要是VC和总酚。不同组织部位实验表明,果皮的抗氧化性最强,果肉次之,果心最弱,且猕猴桃果皮的抗氧化活性主要来源于其中含量丰富的酚类物质,果肉的抗氧化活性主要来源于所含的大量VC。     

In vitro antioxidant activity and phenolic profiles of tropical fruit by-products

Peel and seeds of red-skinned passion fruit, mango, longan, rambutan, white-flesh and red-flesh dragon fruit were screened for their in vitro antioxidant activity, and determination of a detailed profile of phenolic compounds. Rambutan peel and mango seed extracts exhibited the highest total phenolic content and antioxidant activities (DPPH, ABTS and FRAP values). By using UPLC-QTOF-MS/MS analysis, the profiles of soluble and bound phenolics in the fruit by-products were obtained. Ellagic acid, geraniin, quercetin hexoside, gallic and galloyshikimic acid were predominant in rambutan peel, whereas, mangiferin, ellagic acid and galloy(di)glucoside were the major phenolic compounds in mango seed. Main phenolic compounds in longan peel were ellagic acid, galloyldiglucoside, and gallic acid, while in dragon fruit peel this was isorhamnetin glycoside, isorhamnetin glucorhamoside. Meanwhile, rutin and quercetin hexoside were predominant in passion fruit peel. These findings contribute significantly to the database of phenolic profiles of by-products of tropical fruits.     

Nutritional constituents and antioxidant properties of indigenous kembayau (Dacryodes rostrata (Blume) H. J. Lam) fruits

The nutritional and antioxidant properties of peels, pulp and seeds of kembayau (Dacryodes rostrata) fruits were evaluated. Kembayau seeds and pulp were rich in fat, while peels had the highest ash contents. Potassium was the most prevalent mineral in peels (380.72-1112.00 mg/100 g). In kembayau fruits, total flavonoid content (1012.74-28,022.28 mg rutin equivalent/100 g) was higher than total phenolic and total monomeric anthocyanin contents. Kembayau seeds exhibited high flavonoid and phenolic contents compared to the contents in peels and pulp. Antioxidant capacities were also higher in seeds as typified by trolox equivalent antioxidant capacity assay (51.39-74.59 mmol TE/100 g), ferric reducing antioxidant power assay (530.05-556.98 mmol Fe²⁺/100 g) and by 1,1-diphenyl-2-picryl hydrazyl radical scavenging activity (92.18-92.19%) when compared to peels and pulp. Pulp and peels of kembayau fruit may be an important source of energy and minerals for human consumption, while seeds have a good potential as antioxidants.     

Chemical composition and antioxidant activity of Gaylussacia brasiliensis (camarinha) grown in Brazil

This paper presents the centesimal and mineral composition, fatty acid profile of the lipidic fraction, phenolic and anthocyanin contents, and antioxidant activity of Gaylussacia brasiliensis fruit. The results indicated the following composition: moisture (81.30%), lipids (0.62%), proteins (0.56%), carbohydrates (10.74%), dietary fiber (6.53%), and ash (0.25%). The main elements comprising the mineral composition were K, Mg, Ca, and Fe. The fatty acid composition was characterized by a high content of polyunsaturated fatty acids (62.2%) and a high PUFA/SFA ratio (2.92). The G. brasiliensis fruit contained considerable amounts of phenolics (492.87 mgAG/100 g) and anthocyanins (240.43 mg/100 g), which contribute to its high antioxidant activity. This study highlights the potential of this fruit as an important source of both nutritional and bioactive compounds available in the native Brazilian flora.     

Comparative analysis of the chemical composition and antioxidant activity of red (Psidium cattleianum) and yellow (Psidium cattleianum var. lucidum) strawberry guava fruit

Abstract: Strawberry guava (Psidium cattleianum Sabine) is a native fruit of Brazil widely consumed fresh and used in the food industry. In this context, the present study deals with the chemical characterization and the antioxidant activity of the red (Psidium cattleianum) and yellow (P. cattleianum var. lucidum Hort.) strawberry guava fruits, cultivars Irapuã and Ya‐Cy, respectively. Knowledge of chemical composition is fundamental to human nutrition, contributing to the quality of foods. Phenolic compounds in both fruits were analyzed by HPLC–DAD and the total flavonoid content was determined by the Folin–Ciocalteu assay. The antioxidant activity was evaluated by the total reactive antioxidant (TRAP) method. Psidium cattleianum presented a higher content of polyphenolic compounds than P. cattleianum var. lucidum (501.33 and 292.03 mg/100 g, respectively), with hyperoside being one of the major flavonoids identified for both cultivars. In addition to flavonoids, P. cattleianum presented an anthocyanin, identified as cyanidin. The antioxidant activity varied in a concentration‐dependent manner for both strawberry guava species. The volatile oils in fruits and fatty acids in seeds were quantified by GC‐EM. The analysis of the essential oil of yellow strawberry guava was compared with a previous study on the red cultivar, revealing β‐caryophyllene as the main component in both oils. The fatty acid composition was also quite similar and was especially characterized by the presence of unsaturated fatty acids (86.25% and 76%, respectively), among which linoleic acid as the most abundant. Practical Application: In this study, the chemical characterization and the antioxidant activity of the red (Psidium cattleianum) and yellow (P. cattleianum var. lucidum Hort.) strawberry guava fruits were investigated. This is important for potential application of strawberry guava as functional food. Moreover, it may be the experimental basis for further development and use in food industry.     

贮藏温度对耐贮性不同的柑橘品种果皮蜡质含量及其化学组成的影响

为探究果皮蜡质与柑橘果实耐贮性的关系，以广东西江流域著名特产柑橘‘贡柑’（耐贮性较强）、‘砂糖橘’（耐贮性差）果实为试材，采收后装入塑料薄膜保鲜袋中分别在自然室温（（14.2±2.8）℃）和冷库温度（（6.5±0.5）℃）下贮藏90 d，定期检测果实质量损失率、腐烂率、果皮表面结构和蜡质含量及化学组成。结果表明，在不同温度下贮藏，两种柑橘质量损失率和腐烂率显著增加（P＜0.05），表面结构发生改变，果皮蜡质总含量及主要组分（长链脂肪醛、长链脂肪酸、长链脂肪烃、长链脂肪伯醇）含量均显著降低（P＜0.05），冷藏相对于室温贮藏会抑制这些变化，起到关键的保鲜作用。质量损失率、腐烂率均与果皮蜡质总含量及4 类主要组分含量均呈极显著负相关（P＜0.01）；贮藏过程中果皮蜡质不同组分含量的降低幅度存在差异，其中耐贮性较强的‘贡柑’长链脂肪酸含量降幅最大、长链脂肪伯醇含量降幅最小，耐贮性差的‘砂糖橘’长链脂肪伯醇含量降幅最大、长链脂肪酸含量降幅最小；小分子质量的支链烷烃、烯烃和烯醛对贮藏温度的响应更敏感。说明两种柑橘果实的耐贮性与果皮蜡质含量和组分有密切关系。     

油梨品种和部位间抗氧化及乙酰胆碱酯酶抑制活性比较

研究不同品种油梨之间的多酚含量及其抗氧化和乙酰胆碱酯酶抑制活性差异,以期为油梨高价值产品开发提供理论依据。测定热研1号、福尔特、哈斯、里德4种油梨的果皮、果肉、果核3个部位乙醇提取物的总酚含量、抗氧化及乙酰胆碱酯酶抑制活性。结果显示:4种油梨3个部位的总酚含量为9.6~27.8 mg GAE/g干物质。抗氧化及乙酰胆碱酯酶抑制活性均与样品质量浓度存在剂量关系。其中里德的果皮与果核对1,1-二苯基-2-三硝基苯肼自由基、2,2’-联氮-二(3-乙基-苯并噻唑-6-磺酸)二铵盐自由基清除活性以及乙酰胆碱酯酶抑制活性均较强,热研1号与福尔特的果皮、果核对·OH清除活性最强。同一品种内,果皮与果核的活性较强,果肉的活性较差。因此,在产品开发过程中应尽可能地提高果皮、果核这些不可食用部位的利用率,达到变废为宝、提高产品附加值的目的。     

An explorative study on the cell wall polysaccharides in the pulp and peel of dragon fruits (Hylocereus spp.)

The pectic and hemicellulosic cell wall polysaccharides from the pulp and the peel of white-flesh and red-flesh dragon fruits (Hylocereus spp.) were isolated and compared in terms of degree of methoxylation (DM), solubility properties (relative content of uronic acids and neutral sugars in different fractions), neutral sugar composition, molar mass distribution, and affinity toward some specific anti-pectin antibodies. Hereto, the alcohol-insoluble residues were extracted and sequentially fractionated using hot water, a chelating agent, sodium carbonate, and potassium hydroxide solutions to obtain different pectin fractions and a hemicellulose fraction. Chemical analyses were used to characterize these polysaccharide fractions. The results show that cell wall polysaccharides of the pulp and especially of the peel from white-flesh and red-flesh dragon fruits contain significant amounts of pectic substances that are lowly methyl-esterified. The cell wall polysaccharides of the peel as well as those of the pulp contain high amounts (38–47 %) of loosely bound (water-soluble) pectic substances. In the water-soluble fraction (WSF) of the peel samples, uronic acids are the predominant monomers. On the contrary, rhamnogalacturonan-I type neutral sugars, and especially arabinose and galactose, contribute equally, as compared to uronic acid, to the WSF of the pulp samples. Despite the low average DM value of pulp and peel pectin, pectic substances in both samples showed affinity for antibodies with different specificities indicating that a wide range of epitopes, including long blocks of unesterified galacturonic acids (GalA) residues as well as (short) blocks of esterified GalA residues, is present. No large differences between the pectic substances among the different dragon fruit varieties were observed.     

Evaluation of antioxidant properties of pomegranate peel extract in comparison with pomegranate pulp extract

Pomegranate is an important source of bioactive compounds and has been used for folk medicine for many centuries. Pomegranate juice has been demonstrated to be high in antioxidant activity and is effective in the prevention of atherosclerosis. In a previous study, we found that pomegranate peel had the highest antioxidant activity among the peel, pulp and seed fractions of 28 kinds of fruits commonly consumed in China as determined by FRAP (ferric reducing antioxidant power) assay. In this study, we extracted antioxidants from pomegranate peel, using a mixture of ethanol, methanol and acetone, and the antioxidant properties of the extract were further investigated as compared with the pulp extract. The contents of total phenolics, flavonoids, proathocyanidins and ascorbic acid were also measured. The results showed that pomegranate peel extract had markedly higher antioxidant capacity than the pulp extract in scavenging or preventive capacity against superoxide anion, hydroxyl and peroxyl radicals as well as inhibiting CuSO₄-induced LDL oxidation. The contents of total phenolics, flavonoids and proathocyanidins were also higher in peel extract than in pulp extract. The large amount of phenolics contained in peel extract may cause its strong antioxidant ability. We concluded that pomegranate peel extract appeared to have more potential as a health supplement rich in natural antioxidants than the pulp extract and merits further intensive study.