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At least 307 records · Page 17Linked to original sources
PubMed2002

Citrus limonoids and their semisynthetic derivatives as antifeedant agents against Spodoptera frugiperda larvae. A structure-activity relationship study.

The antifeedant activity of Citrus-derived limonoids limonin (1), nomilin (2), and obacunone (3) and their semisynthetic derivatives 4-26 was evaluated against a commercially important pest, Spodoptera frugiperda. Simple chemical conversions were carried out on the natural limonoids obtained from seeds of Citrus limon. These conversions focused on functional groups considered to be important for the biological activity, namely the C-7 carbonyl and the furan ring. In particular, reduction at C-7 afforded the related alcohols, and from these their acetates, oximes, and methoximes were prepared. Hydrogenation of the furan ring was also performed on limonin and obacunone. The known antifeedant properties of the Citrus limonoids are confirmed. Comparison with previously reported data shows that insect species vary in their behavioral responses to these structural modifications. Highly significant antifeedant activity (P < 0.01) for two natural (1 and 3) and three semisynthetic limonoids (4, 8, and 10) was observed against S. frugiperda.

Animals↗
PubMed2003

Transacylation and de-esterification reactions of pectin as catalyzed by pectinesterases from tomato and citrus.

The optimal conditions for the de-esterification reaction of tomato pectinesterase (PE) and citrus PE was 0.1-0.2 M NaCl and at pH 7.5-8.5, 65 degrees C, almost identical to those for the transacylation reaction as observed by turbidity (absorbance at 400 nm) change. Among the PEs tested, pea pod PE presented the most remarkable catalysis on the transacylation reaction, and 1.5% pectin solution was determined to be suitable for this reaction. Low methoxy pectin with a DE (degree of esterification) of 31% displayed a slow turbidity increase, revealing that the extent of DE was influential on the transacylation. Besides citrus pectin, apple pectin was also proved to progress transacylation reaction by PEs from tomato and citrus sources as apparently observed by turbidity method.

Acylation↗
PubMed2003

Changes in molecular weight of transacylated pectin catalyzed by tomato and citrus pectinesterases as determined by gel permeation chromatography.

The changes in molecular masses of pectin in 0.5% pectin-pectinesterase (PE) mixtures (2 units/mL) incubated at various temperatures, pH values, and NaCl levels for 30 min were observed by a Toyopearl TSK HW-65 (F) gel permeation chromatography. The molecular mass of pectin was remarkably increased from 103 to 266 kDa when the incubation temperature of pectin-tomato PE was increased from 25 to 45 degrees C. A further increase in molecular mass was observed when a pectin-citrus PE mixture was incubated at 65 degrees C. The values of pH and NaCl levels were also crucial to the transacylation activity of PEs. Reaction at pH 7.5 with tomato PE and citrus PE remarkably expanded the molecular mass of pectin to 410 and 670 kDa, respectively. The NaCl level of 0.3-0.5 and 0.3 M was favorable for the transacylation reaction of tomato PE and citrus PE, respectively. Only high methoxylpectin was the suitable substrate for PE to conduct the transacylation reaction.

Acylation↗
PubMed2004

Effect of the rootstock and interstock grafted in lemon tree (Citrus limon (L.) Burm.) on the flavonoid content of lemon juice.

The grafting of the rootstock with the lemon tree is an agronomical technique used to improve production and/or quality of the fruit. The interstock has been used with different fruit trees to modulate the tree size, fruit production and quality, and the aging of the tree. The lemon trees grafted with interstocks increase their longevity, lemon production and quality; interstocks are also used to decrease the thickness of the trunk at the grafting point. This enlarging of the trunk provokes a decrease of the sap flow. In our study, "Verna" lemon trees were grafted with interstock between the rootstock and the lemon tree to follow the flavonoid content of the lemon juice. The lemon juice was obtained from the lemons collected of the grafted lemon trees. Two types of rootstocks were used: Citrus aurantium L. and Citrus macrophylla L. Seven interstocks from five cultivars of orange tree, one cultivar of lime tree, and one cultivar of tangerine tree were used. "Verna" lemon trees were also grafted directly to the rootstock. The rootstock was more important agronomic factor than the interstock on the total flavonoid content of lemon juice. The interstock grafting had only a small influence on the flavonoid content of the lemon juice, and it modulated the individual flavonoid content. Citrus aurantium L. rootstock and "Berna" and "Washington Navel" interstocks were the most appropriate to graft in the lemon tree. This interstock grafting technique does not increase the flavonoid content of the lemon juice. Regarding the individual flavonoids, the 6,8-di-C-glucosyl diosmetin was the most affected flavonoid by the type of rootstock used. The interstock used is able to alter the individual quantitative flavonoid order of eriocitrin, diosmin, and hesperidin. In addition, the HPLC-ESI/MS(n) analyses provided the identification of two new flavonoids in the lemon juice: Quercetin 3-O-rutinoside-7-O-glucoside and chrysoeriol 6,8-di-C-glucoside (stellarin-2). The occurrence of apigenin 6,8-di-C-glucoside (vicenin-2), eriodictyol 7-O-rutinoside, 6,8-di-C-glucosyl diosmetin, hesperetin 7-O-rutinoside, homoeriodictyol 7-O-rutinoside and diosmetin 7-O-rutinoside was also confirmed in lemon juice by this technique.

Agriculture↗
PubMed2004

Changes in the levels of polymethoxyflavones and flavanones as part of the defense mechanism of Citrus sinensis (cv. Valencia Late) fruits against Phytophthora citrophthora.

Phytophthora citrophthora causes serious losses in Citrus fruits through brown rot lesion. The effect of infection with P. citrophthora on Citrus sinensis (cv. Valencia Late) fruits was studied, with particular reference to the levels of the flavanones hesperidin and isonaringin and the polymethoxyflavones sinensetin, nobiletin, tangeretin, and heptamethoxyflavone, because flavonoids are most probably involved as natural defense or resistance mechanisms in this genus. Changes in the levels of these flavonoids were detected after infection. The hesperidin and isonaringin contents fell by 13 and 67%, respectively, whereas the contents of their corresponding aglycons, hesperetin and naringenin, increased, suggesting the hydrolyzing effect of this fungus on the glycosylated flavanones. The heptamethoxyflavone, nobiletin, sinensetin, and tangeretin levels increased by 48, 28, 26, and 24%, respectively. The in vitro study revealed that these compounds acted as antifungal agents, the most active being the aglycons (naringenin and hesperetin), followed by the polymethoxyflavones and flavanone glycosides. The participation of these flavonoids in the defense mechanism of this Citrus species is discussed.

Citrus sinensis↗
PubMed2005

Sodium carbonate treatment induces scoparone accumulation, structural changes, and alkalinization in the albedo of wounded citrus fruits.

Following sodium carbonate treatment, accumulation of scoparone (6,7-dimethoxycoumarin) but not scopoletin (6-methoxy-7-hydroxycoumarin) was found in the albedo of wounded fruit from different Citrus sp. and cultivars. Treating wounded mandarin fruit cv. Fairchild with 5% Na(2)CO(3) (SC) lead to a scoparone accumulation in the albedo of 310, 361, and 382 microg g(-1) fresh weight after 7, 10, and 15 days, respectively. Scoparone accumulation was associated with a decrease in decay severity. When oranges cv. Biondo comune wounded and treated with 5% SC were inoculated with Penicillium digitatum or Penicillium italicum conidia 3 days posttreatment, the decay percentage as compared to untreated wounds was reduced by 97.2 and 93.9%, respectively. Observations by scanning electron microscopy of wounded Citrus fruits treated at 20 degrees C with 2, 3, 4, or 5% (w/v) solutions of sodium carbonate showed structural modifications to the albedo as well as damage to 24-48 h old mycelia of P. digitatum, the cause of citrus green mold. Modifications were more evident in orange, lemon, and grapefruit as compared to mandarin fruit. The efficacy of the treatment was strictly related to the SC interaction with the albedo tissue that, in addition to structural changes, significantly increased tissue pH, affecting P. digitatum pathogenicity. The SC remaining as a film on unwounded flavedo had no effect in preventing contact infection by the Penicillia.

Carbonates↗
PubMed2004

Variation in major antioxidants and total antioxidant activity of Yuzu (Citrus junos Sieb ex Tanaka) during maturation and between cultivars.

Epidemiological studies suggest that a high consumption of fruits can reduce the risk of some cancers and cardiovascular disease, and this may be attributable to the antioxidant activity of vitamins and phenolic compounds. The present study investigated the variations in vitamin C, total phenolic, hesperidin, and naringin contents, and total antioxidant activity of yuzu (Citrus junos Sieb ex Tanaka)-which is a popular citrus fruit in Korea and Japan-between cultivars and during maturity. The amounts of phenolics and vitamin C and the antioxidant activity in all tested yuzu cultivars were higher in peel than in flesh. Ripening increased the total antioxidant activity and vitamin C content in both peel and flesh of yuzu. However, the amounts of all total phenolics, hesperidin, and naringin in peel increased with ripening, whereas they decreased slightly in flesh. There was a highly linear relationship between the vitamin C content and the total antioxidant activity in both peel (r(2) = 1.000) and flesh (r(2) =0.998), suggesting that vitamin C plays a key role in the antioxidant activity of yuzu. In addition, the contribution of each antioxidant to the total antioxidant activity of yuzu was determined using a 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging assay and is expressed here in terms of the vitamin C equivalent antioxidant capacity (VCEAC). The means of vitamin C, naringin, and hesperidin in yuzu were 90.4, 63.8, and 65.7 mg/100 g fresh yuzu, respectively. The relative VCEAC values of these compounds were in the following order: vitamin C (1.00) > naringin (0.195) > hesperidin (0.162). Therefore, the estimated contribution of each antioxidant to the total antioxidant capacity of 100 g of fresh yuzus is as follows (in mg of VCEAC): vitamin C (90.36 mg) > naringin (12.44 mg) > hesperidin (10.64 mg). Our results indicate that mature yuzu contains higher amounts of vitamin C and phenolics than other citrus fruits and could therefore be used as a significant dietary source of antioxidants.

Antioxidants↗
PubMed2006

Tyrosinase inhibitory activity of citrus essential oils.

Thirteen kinds of citrus essential oils and their volatile flavor constituents were investigated for tyrosinase inhibitory activity. Eureka lemon, Lisbon lemon, Keraji, and Kiyookadaidai significantly inhibited the oxidation of L-dihydroxy phenylalanine (L-DOPA) by mushroom tyrosinase. Citral and myrcene among volatile flavor constituents of citrus essential oils exhibited tyrosinase inhibitory activities with Ki values of 0.318 and 2.38 mM, respectively. The inhibition kinetics analyzed by a Lineweaver-Burk plot indicated that citral is a noncompetitive inhibitor and myrcene is a competitive inhibitor. These results indicated that citral and myrcene are responsible for the tyrosinase inhibitory activity of citrus essential oils.

Acyclic Monoterpenes↗
PubMed2006

Hydroxylated polymethoxyflavones and methylated flavonoids in sweet orange (Citrus sinensis) peel.

Polymethoxyflavones (PMFs) from citrus genus have been of particular interest because of their broad spectrum of biological activities, including antiinflammatory, anticarcinogenic, and antiatherogenic properties. There have been increasing interests in the exploration of health beneficial properties of PMFs in citrus fruits. Therefore, the isolation and characterization of PMFs from sweet orange (Citrus sinensis) peel will lead to new applications of the byproducts from orange juice processes and other orange consumption in nutraceutical and pharmaceutical products. In our study, eight hydroxylated PMFs, six PMFs, one polymethoxyflavanone, one hydroxylated polymethoxyflavanone, and two hydroxylated polymethoxychalcones were isolated from sweet orange peel and their structures were elucidated by various MS, UV, and different NMR techniques. Some of the hydroxylated PMFs and chalcones are newly isolated from sweet orange peel.

Citrus sinensis↗
PubMed2006

Differences in the carotenoid content of ordinary citrus and lycopene-accumulating mutants.

High-performance liquid chromatography, coupled with photodiode array detection, was used to analyze the carotenoid composition of peel and juice vesicle tissues of ordinary and lycopene-accumulating mutants (referred to as red mutants in this article) of orange, pummelo, and grapefruit. Thirty-six major carotenoids, including some cis-trans isomers, were separated on a C30 reversed phase column, and 23 of them were identified on the basis of retention times and spectral characteristics with authentic standards. Carotenoid profiles varied with tissue types, citrus species, and mutations. beta-Citraurin occurred in the peel of oranges but not in juice vesicles, whereas the reverse was found for violaxanthin, 9-cis-violaxanthin, and luteoxanthin. The diversity of carotenoids in peel and juice vesicle tissues and the fact that there was over 250 times higher content of total carotenoids in peels of Yuhuan pummelo than juice vesicles suggested that the biosynthesis of carotenoids in these two tissues was independent and exchange of carotenoids between the tissues was not likely. Lutein was observed in peels of pummelos and grapefruits and juice vesicles of ordinary pummelo but not in orange tissues. Accumulation of lycopene and beta-carotene was observed in red mutant citrus, except for the peel of Cara Cara red orange. Additionally, phytoene accumulated in all tissues except for the peel of Chuzhou Early Red pummelo. No obvious change in the total content of xanthophylls was observed in the Cara Cara red orange. Ordinary grapefruit (Marsh) tissues and pummelo (Yuhuan) juice vesicles were almost devoid of carotenoids, and in red mutants, the content of total carotenoids increased dramatically up to 790-fold. The different changes in carotenoid content and profiles in mutant(s) of different citrus species suggest that the underlying mechanisms for the mutations might be different.

Carotenoids↗
PubMed1999

Antiproliferative effects of the readily extractable fractions prepared from various citrus juices on several cancer cell lines.

To eliminate the masking effect by flavonoid glycosides, which comprise approximately 70% of conventionally prepared sample, the readily extractable fraction from Citrus juice, which was prepared by adsorbing on HP-20 resin and eluting with ethanol and acetone from the resin, was subjected to antiproliferative tests against several cancer cell lines. Screening of 34 Citrus juices indicated that King (Citrus nobilis) strongly inhibited proliferation of all cancer cell lines examined. Sweet lime and Kabuchi inhibited three of the four cancer cell lines. In contrast, these samples were substantially less cytotoxic toward normal human cell lines.

Antineoplastic Agents, Phytogenic↗
PubMed1999

Factors affecting imazalil and thiabendazole uptake and persistence in citrus fruits following dip treatments.

The effect of concentration, temperature, and length of treatment with imazalil (IMZ) and thiabendazole (TBZ) was studied with application to citrus fruit. The amount of residues retained by fruit after "home" washing was also monitored. IMZ uptake in citrus fruit was related to treatment duration, whereas TBZ residues was not. Residues of IMZ or TBZ fungicides were significantly correlated with dip temperature (r = 0.943 for IMZ; r = 0.911 for TBZ). Treatment at 50 degrees C produced a deposition approximately 8 and approximately 2.5 times higher than when treatments were carried out at 20 degrees C in IMZ and TBZ, respectively. No significant differences in terms of IMZ deposition were detected after treatments carried out alone or in combination. Uptake of the two fungicides was associated with their physicochemical characteristics as well as different formulation types. IMZ residues showed a great persistence during storage when applied separately, and >83% of active ingredient was present after 9 weeks of storage. IMZ residues increased with dip length, doubling when dip time increased from 0.5 to 3 min. In contrast, TBZ residues did not change with the different dip times. Following postharvest dip treatments of citrus fruit at 20 or 50 degrees C, home washing removed approximately 50% of the IMZ and approximately 90% of the TBZ.

Biological Transport↗
PubMed1999

Quantitation of flavonoid constituents in citrus fruits.

Twenty-four flavonoids have been determined in 66 Citrus species and near-citrus relatives, grown in the same field and year, by means of reversed phase high-performance liquid chromatography analysis. Statistical methods have been applied to find relations among the species. The F ratios of 21 flavonoids obtained by applying ANOVA analysis are significant, indicating that a classification of the species using these variables is reasonable to pursue. Principal component analysis revealed that the distributions of Citrus species belonging to different classes were largely in accordance with Tanaka's classification system.

Analysis of Variance↗
PubMed2000

Dehydrothalebanin: a source of resistance from Glycosmis pentaphylla against the citrus root weevil Diaprepes abbreviatus.

Roots of a citrus relative, Glycosmis pentaphylla (orangeberry), were shown to inhibit the growth and survival of larvae of the citrus root weevil Diaprepes abbreviatus. Roots of G. pentaphyllaincorporated into the diet of D. abbreviatus increasingly inhibited the growth of neonate larvae with increased concentration of roots, while roots from citrus rootstocks produced little inhibition. The diet-incorporation assay was used to guide fractionation of an active acetone extract of G.pentaphylla roots. Three major fractions from silica open-column liquid chromatography were active, and these were purified using semipreparative normal-phase HPLC. A single active HPLC subfraction was isolated from each of the three liquid chromatography fractions, and two active compounds were isolated and identified by GC-MSD. GC-MSD and NMR identified one compound as the amide dehydrothalebanin B, and the other was identified by GC-MSD as dieldrin, a chlorinated hydrocarbon insecticide whose origin in our samples is uncertain.

Amides↗
PubMed1997

Induction of a Citrus gene highly homologous to plant and yeast thi genes involved in thiamine biosynthesis during natural and ethylene-induced fruit maturation.

Maturing citrus fruit undergo pigment changes which can be enhanced by exogenous ethylene. In order to identify genes induced by ethylene in citrus fruit peel, we cloned the gene c-thi1. mRNA corresponding to c-thi1 increased gradually in the peel during natural fruit maturation and in response to ethylene. GA3 pretreatment reduced the inductive effect of ethylene. Levels of c-thi1 increased also in juice sacs but the effect of ethylene was much less prominent. c-thi1 is homologous to yeast and plant genes encoding for an enzyme belonging to the pathway of thiamine biosynthesis. The data suggest that thiamine is involved in citrus fruit maturation.

Adenine↗
PubMed1998

A novel protein associated with citrus blight has sequence similarities to expansin.

A protein associated with citrus blight (CB), a disease of unknown cause, was partially characterized. The 12 kDa protein, designated p12, is diagnostic of CB and is present in leaves and xylem fluid from roots and stems of CB-affected trees. The protein, and up to six other CB-specific proteins, are readily detected by SDS-PAGE of xylem fluid from CB-affected trees. The partial N-terminal amino acid sequence of p12 was found to be unique based on database searches. A cDNA library from CB-affected root cambium was screened with a 60 bp fragment, obtained by PCR amplification of cDNA with degenerate primers designed using the amino acid sequence of p12, and two clones were selected. These clones were sequenced revealing a 674 nucleotide cDNA with a 393 nt ORF which included sequence predicted by the N-terminal amino acid sequence of p12. The amino acid sequence based on the p12 ORF was found to be up to 49% similar and 31% identical to expansins. Bacterial expression of the cloned ORF, which encodes an 11.8 kDa protein plus an N-terminal hydrophobic signal peptide, produced an immunoreactive protein of the expected size. By northern blot analysis, it was determined that p12 transcripts are present in root and stem cambium, but not in leaves of CB-affected trees, suggesting transport of the protein to leaves. Southern hybridization analysis of citrus genomic DNA indicated that p12 is a citrus encoded protein.

Amino Acid Sequence↗
PubMed2000

Both point mutation and RNA recombination contribute to the sequence diversity of citrus viroid III.

Field-grown citrus trees often harbor complex mixtures of 4-5 different viroid species, and the presence of citrus viroid III (CVd-III) has been shown to reduce the rate of tree growth without inducing disease. To more fully define the structure of its quasi-species, we have examined nine citrus viroid complexes for the presence of previously undescribed sequence variants of CVd-III. Analysis of 86 full-length cDNAs generated from these nine viroid complexes by RT-PCR revealed the presence of 20 new CVd-III variants. Chain lengths ranged from 293-297 nucleotides, and sequence changes were confined largely to the lower portions of the central conserved region and variable domain. The previously described variants CVd-IIIa (297 nt) and CVd-IIIb (294 nt) were clearly predominant, but phylogenetic analysis indicated that certain isolates may contain representatives of two additional fitness peaks. At least one group of CVd-III variants appears to have arisen as a result of RNA recombination. Populations recovered from diseased/declining trees were the most diverse, but even dwarfing isolates originating from old line Shamouti trees showed considerable variability.

Base Sequence↗
PubMed2001

Assessment of the genetic diversity of Xylella fastidiosa isolated from citrus in Brazil by PCR-RFLP of the 16S rDNA and 16S-23S intergenic spacer and rep-PCR fingerprinting.

The genetic diversity among twenty three strains of Xylella fastidiosa, isolated from sweet orange citrus, was assessed by RFLP analysis of the 16S rDNA and 16S-23S intergenic spacer and by rep-PCR fingerprinting together with strains isolated from coffee, grapevine, plum and pear. The PCR products obtained by amplification of the 16S rDNA and 16S-23S spacer region were digested with restriction enzymes and a low level of polymorphism was detected. In rep-PCR fingerprinting, a relationship between the strains and their hosts was observed by using the BOX, ERIC and REP primers. Two major groups were obtained within the citrus cluster and relationships to the geographic origin of the strains revealed. Citrus strains isolated from the States of São Paulo and Sergipe formed one group and strains from the Southern States formed another group. Distinct origins of X. fastidiosa in the Southern and Southeastern States is postulated. The pear isolate was distantly related to all of the other X. fastidiosa strains.

Brazil↗