Browsing by Subject "Citrus"
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Item Anti-inflammatory Properties of Citrus Limonoids and Their Isolation and Characterization(2012-02-14) Kim, Jin HeeThis dissertation investigates the role of limonoids in inflammation to reduce risk of breast cancer and cardiovascular disease. Radical scavenging activity and apoptotic effects of extracts from lemon seeds were investigated in human breast adenocarcinoma (MCF-7) cells and non-malignant breast (MCF-12F) cells. The MeOH:water (80:20) extract showed the highest (29.1%, P < 0.01) inhibition of MCF-7 cells without affecting the non-malignant breast cells. Further, the purified and modified limonoids were screened for their cytotoxicity on estrogen receptor (ER)-positive (MCF-7) or ER-negative (MDA-MB-231) human breast cancer cells. The MCF-7 cell was more susceptible to tested limonoids. Although most of limonoids induced anti-aromatase activity, the inhibition of proliferation was not related to the anti-aromatase activity. On the other hand, the anti-proliferative activity was significantly correlated with the level of caspase-7 activation by limonoids. The next study investigated the mechanism of anti-breast cancer and anti-aromatase activities of obacunone through inhibition of MCF-7 cell proliferation without affecting non-malignant breast cells. Treatment with obacunone resulted in an increased G1 cell cycle arrest and induction of apoptosis. Exposure of MCF-7 breast cancer cells to obacunone down-regulated expression of inflammatory molecules including nuclear factor-kappa B (NF--2 (COX-2). Furthermore, potential of obacunone on inhibition of COX-2 and NF-the p38 mitogen-activated protein (MAP) kinase was also investigated. In the final study, nomilin was the most potent natural inhibitor for p38 MAP kinase activity in human aortic smooth muscle cells indicating that a seven-membered A ring with acetoxy group, present in nomilin, seems to be essential for its inhibitory activity on p38 MAP kinase. The possible mechanism of nomilin for prevention of cardiovascular disease was determined. Pre-treatment with nomilin resulted in significant inhibition of TNF- induced HASMCs proliferation. The anti-proliferative activity of nomilin is due to apoptosis through mitochondrial dependent pathway.Item Citrus Bioactive Compounds: Isolation, Characterization and Modulation of Bacterial Intercellular Communication and Pathogenicity(2012-07-16) Vikram, AmitThe secondary metabolites of citrus such as limonoids and flavonoids constitute an important part of human diet. The present work was undertaken to elucidate the effect of citrus limonoids and flavonoids on the bacterial cell-cell signaling in Vibrio harveyi, Escherichia coli O157:H7 and Salmonella Typhimurium LT2. The first experiment was focused on purification of limonoids from grapefruit and sour orange seeds. The limonoids were extracted using organic solvents and purified by chromatographic techniques. A total of ten limonoids (7 aglycones and 3 glucosides) were purified. Currently, simultaneous measurement of aglycones and glucosides of limonoids is not available. To address this limitation, an analytical method using high performance liquid chromatography was developed with the capability of measuring both aglycones and glucosides in a single run. Furthermore, its applicability in the fruit and juice samples was demonstrated. The third study investigated the V. harveyi cell-cell signaling inhibitory potential of purified limonoids. Isolimonic acid, ichangin, obacunone and nomilin were showed potent inhibitory activity. Furthermore, isolimonic acid and ichangin inhibit the signal transduction pathway by up-regulating the response regulator luxO. Isolimonic acid was also found to be a potent inhibitor of Escherichia coli O157:H7 cell-cell signaling in the fourth study. The results demonstrated that isolimonic acid inhibits the autoinducer/epinephrine mediated cell-cell signaling, biofilm and virulence in QseBC and QseA dependent fashion. Further investigations using limonin analogues, in the fifth study, demonstrated that the analogue limonin-7-methoxime inhibited the E. coli biofilm in type 1 pili and antigen 43 dependent-fashion, by preventing the binding of the adhesins to plastic surfaces. Another limonoid, obacunone was demonstrated to attenuate the Salmonella virulence by repressing Salmonella Pathogenicity Island 1 (SPI-1) in EnvZ/OmpR dependent mecahnism. The seventh study showed that naringenin, among the flavonoids, was the most potent inhibitor of V. harveyi and E. coli O157:H7 cell-cell signaling. Furthermore, naringenin was found to repress the (SPI-1) in PstS-HilD dependent fashion in the eighth study. In conclusion, the current project identified several limonoids and flavonoids with cell-cell signaling inhibitory property in three bacterial species.Item Physiological Effects of Saline Water on Two Economically Important Horticultural Crops in South Texas(2013-12-02) Simpson, Catherine RossCitrus and watermelons are valuable economic crops worldwide, contributing approximately $120 million combined each year in Texas alone. Both citrus and watermelons are sensitive to saline conditions, which can be problematic in the Lower Rio Grande Valley where they are commonly produced. As Texas increases the percentage of irrigated agriculture each year, and in turn the amount of land potentially exposed to salinization through this practice, grafting salt sensitive plants to tolerant rootstocks becomes a more feasible way to overcome this challenge. Grafting typically improves disease resistance, cold tolerance, yield, fruit quality and has been shown to improve salt tolerance as well. While citrus is commonly grafted to rootstocks that induce desirable qualities in the scion, watermelon grafting is only common in Asia and several European countries due to cost constraints. The main goal of this research was to assess selected rootstocks for salinity tolerance by evaluating plant growth and physiological parameters when subjected to several salinity levels. In the first experiment, potential sour orange replacement rootstocks C22 and C146 were evaluated for salinity as ungrafted trees and grafted to the Olinda Valencia scion. These trees were then compared to the performance of grafted and ungrafted sour orange trees. The results suggest that C22 and C146 rootstocks are more tolerant to saline conditions than sour orange rootstocks at moderate salinity levels. However, grafting significantly decreased all measured growth and physiological parameters for all rootstocks implying that this scion-rootstock combination may not be ideal. In the second experiment, TAMU mini watermelons were grafted to four rootstocks to determine if any of these would improve their performance when subjected to poor quality irrigation water. Of the four rootstocks and ungrafted TAMU mini watermelon, Strong Tosa showed the most growth when subjected to moderate salinity. Salinity treatments were found to increase fruit quality by increasing the percentage of sugar (brix) and fruit flesh firmness.Item Production Systems and Processing Effect on Phytochemicals in Citrus Fruits and Their Analytical and Isolation Methods(2012-12-13) Uckoo, Ram 1980-The emerging scientific evidences on the role of food components in prevention of several chronic diseases are the momentum for shifting from a traditional focus on production to enhancement of nutritional quality. To further understand the role of these phytochemicals this dissertation describes the development of rapid analytical and isolation methods, and the effect of production systems and processing techniques on the levels of phytochemicals in citrus fruits. In the first study, a simultaneous high performance liquid chromatography (HPLC) method for the rapid analysis of amines and organic acids was developed. The simultaneous extraction and analysis of samples provides an economical method for analyzing a large number of samples. In the second study, rapid separation method of potent health beneficial phytochemicals such as polymethoxyflavones from citrus peels using flash chromatography was developed. Using the developed method, five polymethoxyflavones were separated and isolated with high purity in gram level quantity. In the third study, the levels of phytochemicals in organically and conventionally grown lemons and their storage at market simulated conditions were determined. Results suggest that organically produced citrus fruits have higher content of organic acids and flavonoids than conventionally produced. The fourth and fifth study determined the influence of household processing (blending, juicing, hand squeezing techniques) and emerging processing (high pressure processing [HPP], thermal processing) on the phytochemicals content of ?Rio Red? grapefruits. Fruits processed by blending had significantly higher levels of flavonoids, furocoumarins and limonin compared to juicing and hand squeezing, while HPP enabled in extending the shelf life of the processed juice without any adverse effects. Therefore, consuming grapefruit juice processed by blending may provide higher levels of health beneficial phytochemicals. The sixth study describes a rapid flash chromatography method for isolation of PMFs and furocoumarins from citrus industrial by products such as peel oil. In the seventh study the developed method was applied to isolate 10 different phytochemicals from an unexplored citrus species, Miaray mandarin (Citrus miaray TAN.). Among them, the 5,7,8,3',4' pentamethoxyflavone was isolated for the first time from the genus Citrus.Item Symmetric and asymmetric hybridization in citrus spp.(2009-05-15) Bona, Claudine M.The United States is the second largest producer of oranges and grapefruit. However, the US citrus industry experiences constraints in production due to pests, diseases and environmental concerns. Furthermore, due to the low diversity in current commercial scion cultivars any exotic diseases, if introduced into any of the producing states could be devastating. To maintain the US industry competitiveness it is necessary to improve cold, pest and disease resistance to allow expansion of citrus production areas in the US, and to improve fruit quality characteristics such as sweetness, vitamins and phytochemical contents and seedlessness. Sexual hybridization in most Citrus species is complicated because they are highly apomictic. Polyembryony makes it difficult to create large segregating populations for selection. Somatic hybridization by protoplast fusion circumvents sexual incompatibilities and is a powerful tool in genetic improvement. Symmetric and asymmetric hybdridization (gamma irradiation plus iodoacetamide) via protoplast fusion were performed with the objective of producing somatic hybrids of Citrus paradisi with C. sinensis and C. reticulata with C. sinensis. These hybrids could be used for grapefruit improvement and to create genetic diversity. Furthermore, irradiated Swinglea glutinosa microprotoplasts were fused with ?Ruby Red? grapefruit and ?Mucott? tangor to assess the possibility of introgression of pieces of S. glutinosa chromosomes into the recipient protoplasts, a possible first step for radiation hybrid mapping. Double-inactivated fusions (irradiation + iodoacetamide) produced tetraploid and aneuploid plants, and hybridity was confirmed by amplified fragment length polymorphism (AFLP) analysis. This is the first report of obtaining rooted Citrus asymmetric hybrid plants, produced by irradiation plus iodoacetamide. AFLP confirmed presence of S. glutinosa into the receptor genomes, showing a possible donor introgression.