IMPROVING CITRUS NUTRITIONAL PROPERTIES AND QUALITY TO BENEFIT HUMAN HEALTH AND ENHANCE CITRUS UTILIZATION

Progress has been made on three fronts, the metabolomic profiling of fruits, the isolation and characterization of citrus fruit natural products, and the recovery of limonoid glucosides from citrus waste streams. Our metabolomic profiling efforts included supporting ARS scientists from Florida by conducting limonoid analyses on juice samples from HLB infected and non-infected trees. Results from our studies demonstrated that fruit from infected trees possessed higher limonoid aglycones and glucoside concentrations than fruit from non-infected trees. Time course studies monitoring the formation of limonin showed that limonin content surpassed levels acceptable to consumers within several hours following juicing whereas limonin formation in juices from non- infected trees was minimal. Our efforts towards the isolating natural products from citrus have concentrated on isolating a number of compounds needed to complete structural activity studies. The desired compounds were identified as present in a tangelo hybrid and significant progress has been made toward isolating the pure compounds. In regards to isolating limonoid glucosides from waste streams we have continued towards developing green methods for the isolation of individual limonoid glucosides. Studies comparing various reverse phase chromatography resins in combination with different mobile phase conditions have resulted in the development of methods that yield individual limonoid glucosides in high purity. These methods are accomplished using only food grade materials and are thus green. Over the past five year period our efforts have focused on the identification and characterization of bioactive compounds in citrus and related specialty crops, the development of production methods for the commercial-scale isolation of limonoid glucosides, and the evaluation of the health benefits associated with consumption of limonoid glucoside. Analytical methods for the characterization of limonoids have covered each of the three classes of limonoids (aglycones, glucosides, and A-ring lactiones) and spanned from simple colorimetric methods, directed towards supporting commercial producers and packing houses, to more complex LC-MS methods, aimed at assisting researchers. We have used the analytical techniques we developed to characterize multiple citrus samples and to assess the limonoid content of potential feed stocks for the isolation of limonoid glucosides. Working with commercial processors of citrus waste in assessing the effectiveness of their extraction processes, several high limonoid glucoside materials were identified. These materials contained from 6 to 60 percent limonoid glucosides by mass and were subjected to testing as sources for the isolation of limonin glucoside. In order to expedite the testing of these materials and the subsequent isolation of limonin glucoside, we developed a streamlined isolation method. This method relies upon food grade chromatography resins and utilizes only feed grade solvents. This method afforded recoveries in excess of 90% for limonoid glucoside and was used to isolate over 400 grams of material for use in a human study. Significant Activities that Support Special Target Populations Efforts to characterize the bioactive components of mandarin oranges from the Northern California Area have continued. Mandarin growers in this region are all small farms. Accomplishments 01 Maintaining and improving citrus juice quality. Consumption of citrus fruits and juices has been driven by the US industry�s ability to provid consumers with a high quality, good tasting and health-promoting product In order to maintain and increase the utilization of citrus, it is essential to identify the metabolites resulting from pathogenic infectio that detract from fruit quality. ARS scientists in the Processed Foods Unit in Albany, CA, partnered with ARS scientist from the Fort Pierce an Winter Haven Labs in a study to determine how HLB infection influences t limonin and limonoid glucoside concentrations in fruit. From testing fruit samples from HLB plus and minus trees we found that limonoid concentrations in fruit from infected trees were elevated to levels that were detrimental to fruit quality. These results provided important insights into the treatment strategies that should be approached in orde to overcome the impact that HLB infection has on the organoleptic properties of juice. 02 Plant bioactives in Pomegranate Juice. Human health and nutrition can b enhanced by consuming functional foods and beverages, these include fres fruits and vegetables, processed foods, and plant extracts that contain plant bioactive compounds. The presence of functional foods and beverage in the marketplace is dependent upon the availability of robust analytic methods to verify the presence and quality of bioactives, as well as sustainable production and manufacturing practices to produce commercial products that contain plant bioactives. ARS chemists and engineers in th Processed Foods Unit in Albany, CA collaborated together in evaluating green energy efficient methods for extracting bioactives from pomegranat juice byproducts. In the course of this study, an improved analytical method to characterize and quantitative bioactives in pomegranate juice half the time of previous methods was developed. Utilizing this methodology the extraction methods and storage conditions that best preserved the desired bioactives were identified. The analytical method will assist scientists and nutraceutical producers in evaluating the composition and quality of extracts natural product and the extraction conditions developed through this study offer an attractive alternative traditional extraction methods. 03 Genetic basis of plant bioactive compound. Synephrine is a bioactive compound found in some citrus fruits and juices that has promise as an a to weight management and obesity reduction. A functional Tyrosine Decarboxylase (TDC) gene was shown to be essential for synephrine production in Citrus. ARS scientists at WRRC used a combination of chemical and molecular approaches to elucidate the factors controlling synephrine synthesis across Citrus species. Since differences in synephrine production are controlled at a genetic level, results from th study will aid breeders wishing to screen new varieties for their synephrine production potential.