Tuesday, July 31, 2012
Grand Ballroom
This study was initiated to screen a diverse collection of Citrus and related species for total flavonoid concentration and profile, for their potential application in dietary supplements and functional foods. Representatives of the principal horticultural groups of citrus were selected, based on previous knowledge of their flavonoid concentration / profile, or as a focus for new investigations. Samples of whole fruit were harvested in November to March, 2009 and 2010, from the USDA–ARS National Clonal Germplasm Repository/UC Riverside Citrus Variety Collection (Riverside, CA). Fresh fruit were processed by coarse chopping, bag pressing, dehydration in a heated, forced air oven, then milling to produce a powder [40 Mesh = 425 microns]. Powder samples were extracted and analyzed for total flavonoids (TF) and HPLC fingerprint. In total, 47 accessions were sampled at the mature fruit stage, and in 2010, a subset of 5 accessions were sampled at an immature, green fruit stage. TF ranged from 0.3 to 2.1 % (w/w) across the citrons, papedas, and pummelos. Averaged across accessions, sweet oranges (C. sinensis) averaged 4.32%; grapefruit (C. paradisi) averaged 4.16%; mandarins (C. reticulate) averaged 3.95%; and trifoliate oranges (P. trifoliata) averaged 3.19%. Across groups, 6 accessions showed TF >5.0%; 10 accessions showed TF > = 4.0 and <5%; 11 accessions showed TF > = 3.0 to <4.0%; and 20 accessions showed TF <3%. On average, immature (green) fruit showed 1.74X higher TF than the mature fruit of the same accession (8.36 vs 4.81%; n = 5). HPLC fingerprints of selected citrus dehydrates were examined, based on a citrus polyphenol standard panel (flavones and flavanones), including, eriocitrin, rutin, narirutin, naringin, hesperidin, quercetin, nobiletin, and tangeretin at 280 nm. Individual flavonoids varied among groups and species, with hesperidin and naringin the most common and in highest concentration.