Ascorbic acid and flavanone glycosides in citrus: Relationship with antioxidant activity

The effects of cultivar and orchard on the content of ascorbic acid and flavanone glycosides as well as on the antioxidant activity of citrus juices were studied. Ascorbic acid and flavanone glycosides were determined using HPLC method. For antiradicalar activity evaluation, TAEC and ORAC methods were used. Citrus of 'Valencia late' from Faro and 'D. Joao' presented the highest levels of hesperidin in contrast to the citrus of 'Valencia late' from Silves with 0.4 mg/ml, a value closer to those of Navel oranges 'Navelate' and 'Lanelate'. Citrus of 'Valencia late' from Silves and 'D. Joao' presented the lowest levels of narirutin. 'Ortanique' and 'Encore' cultivars were poorer in ascorbic acid compared with the oranges. When the TEAC method was used for the determination of antioxidant activity, 'Valencia late' from Faro presented the best activity. A good relation was observed between antiradical activity measured through the TEAC method and the amount of ascorbic acids in samples. None relation was found between the levels of flavanones and antiradical activity. When the ORAC method was applied, the best activity was found for 'Navelate' and 'Encore' samples and practically none relation between this method and the amounts of ascorbic acid and flavanones was found.

Caraterização dos supressores p20 e p23 do Citrus tristeza virus e avaliação da possibilidade da sua inibição

No presente trabalho pretendeu-se caracterizar a capacidade supressora das proteínas p20 e p23 de diferentes grupos filogenéticos do CTV e o possível silenciamento da p23 de forma a ser incluída numa estratégia de proteção. A atividade supressora local da proteína p23 de todos os grupos filogenéticos foi caracterizada em Nicotiana benthamiana da linha 16C. Todas as proteínas testadas foram capaz de suprimir o silenciamento local, mas não o silenciamento a curta distância. A supressão local mais eficiente verificou-se para a p23 do Gp 5 e a menos eficiente para os isolados dos Gps 2 e M. Surpreendentemente, a p23 do Gp 5 aboliu completamente o silenciamento sistémico, sugerindo que existe uma relação entre a intensidade do silenciamento local e sistémico. A capacidade supressora local conjunta das proteínas p20 e p23 foi avaliada. A coexpressão de ambas as proteínas revelou atividade supressora mais forte comparada com a capacidade de cada proteína individual, mesmo quando inoculada com metade da densidade ótica, sugerindo a existência de sinergismo entre as proteínas p20 e p23. Para analisar as propriedades supressoras a longo prazo, as proteínas p20 e p23 foram inseridas no vetor viral TRV que assegurou a sua disseminação pela planta e expressão por um período mais alargado. Foram observados sintomas em N. benthamiana para todas as modalidades testadas, tais como, nanismo da planta, lesões necróticas severas nas folhas inoculadas e nas folhas novas ligeiros sintomas de mosaico e enrolamento. Contudo, sistemicamente não foram registadas diferenças na capacidade supressora das proteínas p20 e p23. A possibilidade para silenciar sistemicamente a proteína p23 quando incluída num genoma viral foi avaliada através do uso de plantas e enxertos transgénicos para a p23. A estratégia que envolve o uso de enxertos transgénicos parece indicar resultados promissores que conduzem ao silenciamento da p23, contudo, são resultados que devem ser encarados como preliminares.

Regeneración in vitro de naranja agrio (Citrus aurantium Linn)

Tesis (Maestría en Ciencias con Especialidad en Química de Productos Naturales) UANL

Aislamiento, caracterización y evaluación biológica de los constituyentes antituberculosos de la cáscara de citrus aurantifolia.

Tesis (Maestría en Ciencias con Orientación en Farmacia) UANL, 2011.

Efecto de la fertilización orgánica y sintética en el rendimiento y calidad de fruta de toronja (citrus paradisi macf) .

Tesis (Maestría en Ciencias en Producción Agrícola) UANL, 2013.

Studies on weed infestation and tea growth under various weed management methods in a young Tea (Camellia sinensis [L.] kuntze) plantation

A field experiment was conducted in the low country of Sri Lanka, during the period 1994–1995 to investigate the severity of weed infestation and tea growth in relation to weed management methods in newly established tea (Camellia sinensis[L.] Kuntze). Manual weeding (hand and slash weeding) at various intervals was compared with various herbicides, with or without mulching. Weed control with herbicides was superior to that of hand weeding at 6-week intervals or more. Weed control with oxyfluorfen at 0.29 kg ai ha−1 + paraquat at 0.17 kg ai ha−1 or glyphosate at 0.99 kg ai ha−1 + kaolin at 3.42 kg ha−1 were superior. Plots unweeded for 12 weeks or more produced significantly greater (P < 0.05) weed biomass than plots unweeded for 6 weeks. Although the least weed dry weight (P < 0.05) and the greatest number of weed species were recorded with hand weeding at 2 week intervals, there was no particular benefit on tea growth when compared with hand weeding at 6 and 12 week intervals. Inter row mulching in chemically treated plots was more favorable for tea growth than no mulching, while living weed cover in unmulched slash weeded plots suppressed tea growth. A combination of mulching and herbicides, particularly oxyfluorfen and paraquat, followed by hand weeding at least every 6–8 weeks was considered the most appropriate weed management system for young tea.

Interactions between the grasses Phalaris arundinacea, Miscanthus sinensis and Echinochloa crus-galli, and barley and cereal yellow dwarf virusus

The grass species Miscanthus sinensis, Echinochloa crus-galli and Phalaris arundinacea may be useful biomass crops. In glasshouse inoculations with two isolates of Barley yellow dwarf virus (BYDV)-MAV and BYDV-PAV and one of Cereal yellow dwarf virus (CYVD)-RPV , E. crus galli was infected by all three virus isolates, P. arundinacea by BYDV-MAV and CYDV-RPV, but M. sinensis only by BYDV-MAV. All three hosts became very difficult to infect after several weeks’ growth. Symptoms were inconspicuous; dry matter yield losses ranged from c. 20–40%. Aphids acquired all three virus isolates from E. crus-galli, but more efficiently from 5 than 26-week-old plants. Only BYDV-MAV was acquired from P. arundinacea and M. sinensis. Plants of each species and of Avena sativa were grown outdoors between May and July in 1994 and 1995. Young plants of each species were exposed for successive 2-week intervals during the same periods. Vector populations were higher on A. sativa and P. arundinacea than on E. crus-galli and M. sinensis, and more plants of these species became infected. In 1994 only BYDV-MAV was detected. In 1995 BYDV-MAV, BYDV-PAV and CYDV-RPV were all detected; BYDV-MAV was again the virus isolate most frequently found.

The citrus flavanone naringenin inhibits inflammatory signalling in glial cells and protects against neuroinflammatory injury

Neuroinflammation plays an integral role in the progression of neurodegeneration. In this study we investigated the anti-inflammatory effects of different classes of flavonoids (flavanones, flavanols and anthocyanidins) in primary mixed glial cells. We found that the flavanones naringenin and hesperetin and the flavols (+)-catechin and (-)-epicatechin, but not the anthocyanidins cyanidin and pelargonidin, attenuated LPS/IFN-gamma-induced TNF-alpha production in glial cells. Naringenin also inhibited LPS/IFN-gamma-induced iNOS expression and nitric oxide production in glial cells, thus showing the strongest antiinflammatory activity among all flavonoids tested. Moreover, naringenin protected against inflammatory-induced neuronal death in a primary neuronal-glial co-culture system. Naringenin also inhibited LPS/IFN-gamma-induced p38 mitogen-activated protein kinase (MAPK) phosphorylation and downstream signal transducer and activator of transcription-1 (STAT-1) in LPS/IFN-gamma stimulated primary mixed glial cells. Taken together, our results suggest that naringenin may produce an anti-inflammatory effect in LPS/IFN-gamma stimulated glial cells that may be due to its interaction with p38 signalling cascades and the STAT-I trascription factor. (C) 2009 Elseiver Inc. All rights reserved.

Green tea (Camellia sinensis) catechins and vascular function

The health benefits of green tea (Camellia sinensis) catechins are becoming increasingly recognised. Amongst the proposed benefits are the maintenance of endothelial function and vascular homeostasis and an associated reduction in atherogenesis and CVD risk. The mounting evidence for the influential effect of green tea catechins on vascular function from epidemiological, human intervention and animal studies is subject to review together with exploration of the potential mechanistic pathways involved. Epigallocatechin-3-gallate, one of the most abundant and widely studied catechin found in green tea, will be prominent in the present review. Since there is a substantial inconsistency in the published data with regards to the impact of green tea catechins on vascular function, evaluation and interpretation of the inter- and intra-study variability is included. In conclusion, a positive effect of green tea catechins on vascular function is becoming apparent. Further studies in animal and cell models using physiological concentrations of catechins and their metabolites are warranted in order to gain some insight into the physiology and molecular basis of the observed beneficial effects.

The differential tissue distribution of the citrus flavanone naringenin following gastric instillation

Citrus flavonoids have been investigated for their biological activity, with both anti-inflammatory and -carcinogenic effects being reported. However, little information is known on the bioavailability of these compounds in vivo. The objectives of this study were to determine the tissue distribution of naringenin after gastric gavage of [H-3]-naringenin to rats. Unlabelled naringenin was also used to quantify the levels of naringenin and its major metabolites in tissues and eliminated in the urine and faeces. Significant radioactivity was detected in the plasma as well as all tissues examined 2 h post-gavage. After 18 h, higher levels of radioactivity were retained in plasma and tissues (55% of the administered radioactivity). Investigation of the nature of metabolites, using unlabelled naringenin, revealed that the glucuronides were the major components in plasma, tissues and urine, in addition to the colonic metabolite 3-(4- hydroxyphenyl) propionic acid, detected in the urine. The aglycone was the form extensively retained in tissues after 18 h post-gavage. Total identified metabolites detected after 18 h in most tissues were only 1-5% of the levels detected after 2 h. However, the brain, lungs and heart retained 27, 20 and 11%, respectively, relative to the total metabolites detected at 2 h. While radioactive detection suggests increased levels of breakdown products of naringenin after 18 h versus 2 h, the products identified using unlabelled naringenin are not consistent with this, suggesting that a predominant proportion of the naringenin breakdown products at 18 h are retained as smaller decomposition molecules which cannot yet be identified.

Detection of citrus canker in citrus plants using laser induced fluorescence spectroscopy

Citrus canker is a serious disease caused by Xanthomonas citri subsp. citri bacteria, which infects citrus plants (Citrus spp.) leading to a large economic loss in citrus production worldwide. In Brazil citrus canker control is done by an official eradication campaign, therefore early detection of such disease is important to prevent greater economic losses. However, detection is difficult and so far it has been done by visual inspection of each tree. Suspicious leaves from citrus plants in the field are sent to the laboratory to confirm the infection by laboratory analysis, which is a time consuming. Our goal was to develop a new optical technique to detect and diagnose citrus canker in citrus plants with a portable field spectrometer unit. In this paper, we review two experiments on laser induced fluorescence spectroscopy (LIF) applied to detect citrus canker. We also present new data to show that the length of time a leaf has been detached is an important variable in our studies. Our results show that LIF has the potential to be applied to citrus plants.

The Xanthomonas citri effector protein PthA interacts with citrus proteins involved in nuclear transport, protein folding and ubiquitination associated with DNA repair

P>Xanthomonas axonopodis pv. citri utilizes the type III effector protein PthA to modulate host transcription to promote citrus canker. PthA proteins belong to the AvrBs3/PthA family and carry a domain comprising tandem repeats of 34 amino acids that mediates protein-protein and protein-DNA interactions. We show here that variants of PthAs from a single bacterial strain localize to the nucleus of plant cells and form homo- and heterodimers through the association of their repeat regions. We hypothesize that the PthA variants might also interact with distinct host targets. Here, in addition to the interaction with alpha-importin, known to mediate the nuclear import of AvrBs3, we describe new interactions of PthAs with citrus proteins involved in protein folding and K63-linked ubiquitination. PthAs 2 and 3 preferentially interact with a citrus cyclophilin (Cyp) and with TDX, a tetratricopeptide domain-containing thioredoxin. In addition, PthAs 2 and 3, but not 1 and 4, interact with the ubiquitin-conjugating enzyme complex formed by Ubc13 and ubiquitin-conjugating enzyme variant (Uev), required for K63-linked ubiquitination and DNA repair. We show that Cyp, TDX and Uev interact with each other, and that Cyp and Uev localize to the nucleus of plant cells. Furthermore, the citrus Ubc13 and Uev proteins complement the DNA repair phenotype of the yeast Delta ubc13 and Delta mms2/uev1a mutants, strongly indicating that they are also involved in K63-linked ubiquitination and DNA repair. Notably, PthA 2 affects the growth of yeast cells in the presence of a DNA damage agent, suggesting that it inhibits K63-linked ubiquitination required for DNA repair.

Proteomic analysis reveals suppression of bark chitinases and proteinase inhibitors in citrus plants affected by the citrus sudden death disease

Citrus sudden death (CSD) is a disease of unknown etiology that greatly affects sweet oranges grafted on Rangpur lime rootstock, the most important rootstock in Brazilian citriculture. We performed a proteomic analysis to generate information related to this plant pathogen interaction. Protein profiles from healthy, CSD-affected and CSD-tolerant stem barks, were generated using two-dimensional gel electrophoresis. The protein spots were well distributed over a pI range of 3.26 to 9.97 and a molecular weight (MW) range from 7.1 to 120 kDa. The patterns of expressed proteins on 2-DE gels made it possible to distinguish healthy barks from CSD-affected barks. Protein spots with MW around 30 kDa and pI values ranging from 4.5 to 5.2 were down-regulated in the CSD-affected rootstock bark. This set of protein spots was identified as chitinases. Another set of proteins, ranging in pI from 6.1 to 9.6 with an MW of about 20 kDa, were also suppressed in CSD-affected rootstock bark; these were identified as miraculin-like proteins, potential trypsin inhibitors. Downregulation of chitinases and proteinase inhibitors in CSD-affected plants is relevant since chitinases are well-known pathogenesis-related protein, and their activity against plant pathogens is largely accepted.