Phytochemical Profile and Antioxidant Activity of Physiological Drop of Citrus Fruits

Abstract: The phytochemical content and the antioxidant activity (AA) of physiological drop of the main citrus species grown in China were investigated. Among the flavonoids, hesperidin was found mostly in mandarin and sweet orange, naringin was found mostly in sour orange, pummelo, grapefruit and a hybrid (Gaocheng), narirutin was found in most varieties, neohesperidin was found in Gaocheng and Huyou, and nobiletin and tangeretin were found in most varieties. Hydroxycinnamic acids were the main phenolic acids present, ferulic acid and caffeic acid were the dominant in most cases. There was a greater amount of free (extractable) than bound (insoluble) phenolic acids. Levels of limonoids were higher in Foyou, Eureka lemon, and Gaocheng than those in the other cultivars. The highest level of synephrine was found in Ponkan and Weizhang Satsuma. AA was highest in Ponkan and Weizhang Satsuma and lowest in Huyou, pummel, and lemon. These results suggest that physiological drop of citrus fruits have good potential as sources of different bioactive compounds and antioxidants. Practical Application: Physiological drop of citrus fruits may be a good resource of bioactive compounds including flavonoids, phenolic acids, limonoids, synephrine, and a good material of nutraceuticals.     

Improvement of the Half-embryo Test for Detection of Gamma-irradiated Grapefruit and Its Application to Irradiated Oranges and Lemons

The duration of the half-embryo test used for identification of gamma-irradiated grapefruit was shortened by increasing germination temperature to 35°C. Maximum shooting percentages were reached within 3 days. Gibberellin application reduced the required incubation time to 2 days. Half-embryos extracted from irradiated orange and lemon gave similar results to those of grapefruit. This half-embryo test is proposed as an identification method for irradiated citrus. Assessment can be made after 3 to 4 days when shooting percentage is greater than 50%.     

The effects of nanoemulsions based on citrus essential oils (orange,mandarin, grapefruit,and lemon) on the shelf life of rainbow trout (Oncorhynchus mykiss) fillets at 4 ± 2°C

This study investigated the antioxidant and antimicrobial effects of nanoemulsions of orange, grapefruit, mandarin, and lemon essential oils on rainbow trout fillets stored at 4 ± 2°C in refrigerator. The results demonstrated that the shelf life of the rainbow trout fillets was determined as 10 days for the control group, 12 days for the tween 80 (surfactant), 14 days for orange and lemon treatment groups, and 16 days for mandarin and grapefruit groups. Nanoemulsions based on essential oils removed the fishy odor and had a positive effect on organoleptic quality. The use of citrus essential oil-based nanoemulsions decreased the values of biochemical parameters and slowed the growth of bacteria compared to the control group. Among all treatment groups, only the control group exceeded the TVB-N limit value on the 12th day of storage. PV and FFA values in fillets treated with mandarin and grapefruit nanoemulsions developed more slowly during the storage period. In addition, the lowest bacteria counts were found in the mandarin and grapefruit treatment groups. It can be concluded that especially mandarin and grapefruit EOs in all citrus essential oils can be recommended for preparing nanoemulsions in the preservation of rainbow trout fillets.     

Simultaneous determination of N-methylcarbamates and their metabolites in citrus fruits by HPLC avoiding use of halogenic solvents

Twenty-one N-methylcarbamates (NMCs) and 12 of their metabolites or isomers in citrus fruits were simultaneously determined avoiding use of dichloromethane. NMCs in lemon, orange, and grapefruit were extracted with acetone, then the acetone was evaporated off and sodium chloride was added before extraction with ethyl acetate. The extract was evaporated and the residue was cleaned up on a combined mini-column set of Supelclean ENVI-Carb and Mega Bond Elut SAX cartridges. NMCs were determined by HPLC with post-column reaction and fluorescence detection. All of the NMCs in the orange sample were determined without interfering peaks. However 8 NMCs in lemon extract and 10 NMCs in grapefruit extract were not detected because interfering peaks appeared at similar retention times to those of the NMCs. These NMCs were determined using LC/MS (SIM) and were well recovered. Eighty-three data sets obtained by HPLC and LC/MS showed good similarity, with r2 = 0.9178. Recoveries were 60.1 to 97.8% for major NMCs at a fortification level of 0.1 ppm. The limit of detection by HPLC was 0.005 ppm NMCs in samples and a similar level applied to LC/MS.     

Non-conventional techniques to obtain grapefruit jam

Different grapefruit jams obtained by conventional, osmotic dehydration (OD) without thermal treatment and microwave (MW) techniques were compared. A kinetic study was previously carried out to characterize the fruit OD process in order to manufacture OD jams. Fibres from bamboo, apple and orange were incorporated into OD jams. Soluble solids, moisture, water activity, pH, consistency, flow properties and colour were evaluated for all jams. The jams obtained by the OD process had a colour more similar to the fresh fruit than the heated ones, but the addition of fibre was necessary to improve the consistency. However, the MW procedure affects colour in a similar way to conventional heating but increases the consistency of the samples.Industrial relevanceThe consumption of grapefruit may be as fresh fruit, juice or jam. The application of prolonged heat treatments to the fruit, such as in the case of jams and juices, can lead to important losses of the beneficial properties of this citrus fruit. Osmotic dehydration at mild temperature is a technique that could be used to obtain jam without being so aggressive to the fruit. On the other hand, the use of microwave energy has been proposed as an alternative to traditional heat pasteurisation in order to better preserve the natural organoleptic characteristics and essential thermolabile nutrients of grapefruit juice, due to the shorter processing time required. In this work the quality of different grapefruit jams obtained by applying alternative procedures to the conventional one has been compared. Osmotic dehydration and microwave energy were applied as alternatives to conventional heating and bamboo, apple and orange fibres were added and compared with conventional pectin. The osmotic dehydration procedure used produces jams with lower sugar content but with a colour very similar to that of the fresh fruit. Nevertheless, fibre should be added to improve the consistency of the samples, bamboo exhibiting the flow properties most similar to conventional jam. On the other hand, microwaves affect the colour of the product in a similar way to conventional heating but increase the consistency of jams.     

五种柑橘属水果膳食纤维功能特性及微观结构研究

以脐橙、葡萄柚、柠檬、贡柑和椪柑五种柑橘属水果的果皮为试材,比较了果皮中膳食纤维（DF）功能特性和微观结构的差异。结果表明：五种膳食纤维成分的功能特性和微观结构存在显著差异。葡萄柚DF具有最高的胆酸钠吸附量（877.69±13.32mg/g）,胆固醇吸附量（10.88±0.32mg/g [pH2.0],17.90±0.17mg/g [pH7.0]）,α-淀粉酶活力抑制率（56.73%）和胰脂肪酶活力抑制率（32.5%）。在胃的酸性环境下,椪柑DF具有最高的NO2-清除率（36.40%）。脐橙DF中主要单糖是葡萄糖（33.87%）,而其他四种柑橘属DF中主要单糖是阿拉伯糖,其中葡萄柚DF中阿拉伯糖最高（44.83%）。通过扫描电镜观察,葡萄柚和椪柑DF表面更加不规则、粗糙,并且蜂窝状结构更致密伴随大量裂缝和孔隙。     

Analysis of natural citrus aqueous essences

Commercially produced natural citrus aqueous essences obtained from orange, grapefruit, lemon and lime were qualitatively analyzed by GC-MS system. The major and most of the minor components had been previously isolated from these fruits. Also some minor components, not previously found were identified in this study.     

Characteristics of Israeli Citrus Peel and Citrus Juice

Data on the composition of Israeli orange juice, grapefruit juice, orange peel and grapefruit peel were analyzed. Significant differences were found mainly between the juice and peel in the content of isocitric acid, ash, minerals, total pectin, total flavonoids, chlorides, phosphates, chloramine-T number and arginine. The significance of these findings in detecting juice adulteration with peel extract solids is discussed. The chemical and amino acids characteristics of the citrus products analyzed may be used to establish guidelines required for detecting citrus juice adulteration.     

蜂蜜中原蜜黄酮类化合物HPLC图谱比较分析

利用高效液相色谱比较分析不同蜂种、不同产地、加工与否以及不同蜜源蜂蜜中原蜜黄酮类化合物的种类及含量差异。结果表明,意大利蜜蜂油菜原蜜和中华蜜蜂油菜原蜜总峰数和峰形都比较相似,意大利蜜蜂油菜原蜜的总黄酮含量比中华蜜蜂油菜原蜜总黄酮含量高。不同产地的意大利蜜蜂油菜原蜜的图谱峰形整体相似,总黄酮含量和黄酮类化合物种类大致相同。加工后的商品蜜总黄酮含量减少,黄酮类化合物的种类也减少,商品蜜的高效液相色谱图显示其黄酮类化合物的出峰时间靠前,主要密集分布在水溶性的分离相中。3个不同蜜源蜂蜜原蜜黄酮类化合物高效液相色谱图的总峰数和峰形都有较大差异,油菜原蜜、洋槐原蜜及柑橘原蜜的总峰数分别为65、58、70个,柑橘原蜜的总黄酮含量最高,达161.62μg/100 g。单花蜂蜜原蜜黄酮类化合物的高效液相色谱图峰形具有一定的特异性,可以作为指纹图谱用于蜂蜜蜜源的鉴定。     

HPLC Analysis of Sorbic Acid in Citrus Fruit

A method for the determination of sorbic acid (2,4-hexadienoic acid) in citrus fruit is described. The method consists of extraction of the peel with methanol, clean-up of the extract by solvent partitioning and column chromatography, and quantitative determination by reverse-phase HPLC using UV detection. The method is applicable to orange, lemon, and grapefruit and the detection limit is 0.5 ppm. Analysis of fruit fortified with 1–10 ppm sorbic acid indicated an average recovery of 95.6% with a coefficient of variance of 2.9%.     

Hesperetin: A marker of the floral origin of citrus honey

Seventeen flavonoid aglycones were identified in various experimental and commercial citrus honey samples by HPLC analysis. The flavanone hesperetin was detected in all samples. This flavanone was not detected in any of the honey samples, from diverse floral origin (including rosemary, lavender, sunflower, almond, sweet chestnut, white clover, Erisarum, Robinia, Rhododendron, Tilia, Prosopis, Eucalyptus and Calluna honeys) previously investigated. The analysis of the flavonoids present in orange nectar revealed that the flavanone hesperidin (hesperetin-7-rutinoside) was the major flavonoid detected and, therefore, this should be the main source of the hesperetin found in citrus honey. Hesperetin should be produced by hydrolysis of hesperidin by the bee enzymes present in honey. These results suggest that hesperetin could be used as a marker for the botanical origin of citrus honey.     

Limonoid Glucosides in Commercial Citrus Juices

Commercial citrus juices were found to contain very high concentrations of limonoid glucosides. TLC analyses showed the presence of these compounds averaging 320, 190 and 82 ppm in orange, grapefruit and lemon juices, respectively. The major glucoside in citrus juices was limonin 17-O-β-D-glucopyianoside, which constituted over 50% of the total limonoid glucosides in the juices.     

制粒对柑橘全果果粉酚类物质及抗氧化活性的影响

目的：了解制粒前后柑橘全果果粉酚类物质及抗氧化活性的变化,评价制粒对柑橘全果果粉营养价值的影响。方法：以不同柑橘类型的4 个代表品种为试材,利用高效液相色谱（high performance liquid chromatography,HPLC）检测分析各品种柑橘全果果粉制粒前后酚类物质的种类和含量变化,利用铁离子还原/氧化（ferric reducing/antioxidant power,FRAP）法、1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）法和2,2’-联氮双（3-乙基苯并噻唑啉-6-磺酸）二铵盐（2,2’-azinobis-（3-ethylbenzthiazoline-6-sulphonate）,ABTS）法对其抗氧化活性进行评价。结果：与制粒前相比,制粒后各品种柑橘全果果粉的总酚和总黄酮含量多数无明显变化。不同种类多酚和黄酮类物质含量的变化如下：脐橙全果果粉的绿原酸、川陈皮素含量在制粒后明显下降（P＜0.05）;澳柑全果果粉的没食子酸、绿原酸、柚皮苷含量在制粒后明显下降（P＜0.05）;葡萄柚全果果粉的阿魏酸、柚皮苷、芦丁、地奥司明、甜橙黄酮含量在制粒后均明显下降（P＜0.05）。体外抗氧化活性实验表明,ABTS法、DPPH法、FRAP法所测定的抗氧化活性结果相对一致,且大多数品种的柑橘全果果粉制粒前后抗氧化活性无显著变化（P＞0.05）。35～40 ℃制粒工艺不但没有明显改变柑橘全果果粉的酚类物质组成与含量,也未降低其抗氧化能力。结论：制粒未造成柑橘全果果粉营养品质的下降,这种微加工方式可以实现对柑橘全果的有效利用。     

Analysis of sterols: a novel approach for detecting juices of pineapple,passionfruit, orange and grapefruit in compounded beverages

Direct GC/MS analysis of the hexane extracts of fruit juices provides an efficient means for demonstrating that very different sterol patterns exist in the juices of pineapple, passionfruit and the two citrus fruits, orange and grapefruit. Ergostanol and stigmastanol were found to be the sterol markers for pineapple juice, while passionfruit juice was characterised by the presence of an unidentified but unique sterol referred to as compound C. Juices of orange and grapefruit yielded very similar sterol profiles. They were readily distinguished from pineapple and passionfruit juices by a higher stigmasterol/campesterol ratio. Valencene/nootkatone response ratio in the hexane extracts was employed to aid in the differentiation of the two citrus juices. Matrix effects on the determination of sterol and sesquiterpenoid distributions were found to be insignificant. Although natural variation and absolute uniqueness of the sterol profile for each of the four fruit juices were not established due to the relatively small number of fruit samples examined, the results of several compounded beverages clearly point to the potential usefulness of sterol profiles for detecting juices of orange, grapefruit, pineapple and passionfruit in mixed drinks. © 1998 SCI.     

Bioactive compounds and antioxidant activity of citrus juices produced from varieties cultivated in Calabria

Juices from 15 citrus varieties (six oranges, one lemon, two grapefruit, three bergamot, one cedar, one mandarin and one chinotto) from Calabria (Italy) were investigated mainly on quality parameters, total flavonoids, total phenolic compounds, total anthocyanin, ascorbic acid and antioxidant capacity (ABTS and DPPH assay). Total phenolic compounds had highest values, ranging from 1.54 mg/mL and 1.43 mg/mL respectively for pink grapefruit (PG) and yellow grapefruit (YG), to 0.92 and 0.96 mg/mL for cedar (C) and mandarin (Ma) respectively. Total anthocyanins ranged from 0.31 μg/mL yellow grapefruit (YG) to 3.51 μg/mL tarocco (T). Total flavonoids ranged from 0.09 mg/mL tarocco (T) to 0.24 mg/mL castagnaro (BC). In general the three cultivars of bergamot (BFe, BC and BF) have the greatest amount of flavonoids. All the analysed samples exhibit a good content of bioactive compounds.     

Using flavonoids, phenolic compounds and headspace volatile profile for botanical authentication of lemon and orange honeys

This study evaluates the usefulness of flavonoids (naringenin, hesperetin, chrysin, galangin, kaempferol, luteolin, pinocembrin, and quercetin) and phenolic acids (caffeic acid and p-coumaric acid) together with 37 volatile compounds in the differentiation between lemon blossom honey (Citrus limon) and orange blossom honey (Citrus spp.). The total content of flavonoids and phenolic acids is twice as high in lemon honey (6.20 mg/100 g) as in orange honey (3.64 mg/100 g); naringenin and caffeic acid were the main compounds in all cases. Hesperetin, a floral marker of citrus honey, was not significantly different for the two types of honey. A multivariate PLS2 analysis showed that some volatile compounds such as, 4 lilac aldehydes and bencenacetaldehyde (all abundant in orange honey) were negatively correlated with 4 flavonoids: pinocembrin, chrysin, naringenin and quercetin, and caffeic phenolic acid (all abundant in lemon honey). Moreover, the last 5 compounds were positively correlated with: 6 alcohols, 2 ketones, acetaldehyde and furanmethanol. This is a first approach to employ all of these compounds together with appropriate statistical techniques to differentiate between two varieties of citrus honey, and therefore it could be an interesting tool for their authentication.     

The effects of nanoemulsions based on citrus essential oils on the formation of biogenic amines in trout fillets stored at 4 ± 2°C

The influences of nanoemulsions based on citrus peel (orange, lemon, mandarin, and grapefruit) essential oils on the biogenic amine (BA) formation in rainbow trout (Oncorhynchus mykiss) fillets stored 4 ± 2°C were investigated. The results demonstrated that main BAs in the trout fillets were putrescine, cadaverine, spermidine, spermine, serotonin, tyramine, dopamine, and agmatine. It was determined that nanoemulsion application had generally suppressive effect on the formation of BAs during storage. It was also found that especially orange and lemon nanoemulsion groups were effective on histamine formation. Histamine values ranged from 0.00 to 4.08 in all groups during storage and the levels were below the limit values of FDA and EU throughout the storage period for all treatment groups. Similarly, Quality Index (QI) values of BAs were found to be below legal limits in all groups. Consequently, it was found that nanoemulsions prepared from essential oils kept the BA formation at a lower level during storage.     

Clean recovery of antioxidant flavonoids from citrus peel: Optimizing an aqueous ultrasound-assisted extraction method

One of the main reasons for unsuccessful recovery of flavonoids from citrus by-products is the absence of effective extraction procedures. In this work, flavonoid fractions were obtained from citrus peels (lime, orange and tangerine) growing in South American cultivars using an optimized aqueous ultrasound-assisted extraction method with high yield (40.25 ± 12.09 mg of flavonoid fraction/g peel). Total phenolic content in flavonoid fractions obtained from different sources was 74.80 ± 1.90, 66.36 ± 0.75 and 58.68 ± 4.01 mg GAE (gallic acid equivalents)/g, for lime, orange and tangerine, respectively.The composition of flavonoid fractions was established by using HPLC/MS. Orange peel contained hesperidin, neohesperidin, diosmin, nobiletin and tangeritin, being the most complex source. Tangerine peel was the simplest source and contained only hesperidin and neohesperidin. Using the thiobarbituric acid-reactive substances (TBARS) assay it was demonstrated that all flavonoid fractions were able to inhibit cupper (Cu²⁺) or peroxynitrite (ONOO⁻) induced human low density lipoprotein (LDL) oxidation. Differences in the antioxidant activity of individual components from flavonoid fractions were also observed.     

柑橘精油的抑菌性及D-柠檬烯在面包的初步应用研究

研究商品柑橘精油及D-柠檬烯对大肠杆菌、金黄色葡萄球菌、枯草芽孢杆菌、酵母、毛霉、青霉的抑菌性,并对D-柠檬烯在面包上做初步应用研究。试验结果表明:样品以液体作用方式的抑菌大小为D-柠檬烯>柠檬油>柚油>橙油;以气体作用方式时只有D-柠檬烯对酵母、青霉能形成抑菌圈;D-柠檬烯应用于面包时,其气体抑菌效果较好。     

Comparative study on the carotenoid composition of the peel and the pulp of different citrus species

The carotenoid compositions of the peel and the pulp of various citrus fruits were compared with HPLC methods using C18 and C30 columns. The extracts usually contain β-cryptoxanthin and lutein in considerable amounts and in all species except lime, the red apocarotenoid β-citraurin as well. In case of lime and mandarin the carotenoid compositions of peel and pulp show a good coincidence while in orange, clementine, grapefruit, lemon and kumquat there are a lot more differences. Lime extracts contain practically only two carotenoids: β-carotene and lutein. The carotenoid components of the saponified extracts of kumquat were separated on calcium carbonate columns and were investigated in detail. The components were identified with HPLC–DAD and HPLC–MS.Industrial relevanceCitrus fruits are important starting materials for juice production. Their carotenoid fingerprint shows differences not only in different species but the proportion of certain pigments can be different in the same fruit according to where the plants were grown and how they were processed. Comparison of the carotenoid content of different fruit products (e.g. juices) can give us useful hints about the quality of the product and about the amount of these important natural antioxidants.