Analysis of antioxidant compounds in sweet orange peel by HPLC–diode array detection–electrospray ionization mass spectrometry

Abstract

HPLC-diode array detection-electrospray ionization mass spectrometry was used to determine qualitatively and quantitatively the flavonoid content of several fractions and residues of extracts of Greek navel sweet orange peel (Citrus sinensis) from the region of southern Greece (Leonidi-Tripoli). The main groups of flavonoids found according to HPLC retention times, spectral data and literature references were polymethoxylated flavones, C-glycosylated flavones, O-glycosylated flavones, O-glycosylated flavanones, flavonols and phenolic acids and their derivatives. The ethyl acetate fraction which has been shown in previous work to possess the best radical scavenging activity among the others was found to contain C-glycosylated flavones, polymethoxylated flavones, O-glycosylated flavones, O-glycosylated flavanones, two phenolic acid derivatives and two unknown compounds, all in low concentrations. The group of C-glycosylated flavones was reported for the first time in the peel of Navel sweet orange. The C-glycosylated flavones found according to their spectral characteristics and literature were 6-C-beta-glucosyldiosmin, 6,8-di-C-glucopyranosylapigenin, 6,8-di-C-beta-glucosyldiosmin and two unknown. The results suggest that the ethyl acetate fraction of navel Citrus sinensis peel consists of significant antioxidant compounds and can be used as a food additive of natural origin or a pharmaceutical supplement using as a source of peel the byproducts of the orange juice industry.

Influence of postharvest processing and storage on the content of phenolic acids and flavonoids in foods

“…Indeed, in the mandarin type citrus fruit, ponkan (Citrus reticulata), polymethoxylated flavones like nobiletin, tangeretin and sinensetin were found, in decreasing order, in flavedo, albedo and segment membrane, while in juice sacs these compounds were not detected [143]. This is in agreement with the characteristics of flavonoids in the peel of citrus fruits which is rich in polymethoxylated-, C-glycosylated-and O-glycosylated flavones [142,143].…”

“…Grapefruits [124,126], buckwheat [131], rooibos tea [117], artichokes [132], honey [133], parsley [134], olives [85,134,135], lemons [129,130,136], lettuce [137], pepper [137], chicory [137], wine [138,139], grape juice [7], grapes [124], wheat [140], plums [124], peas [124], bamboo leaves [64,141], oranges [5,66,124,142], ponkan (mandarin-type) [143], tangerine essential oils [144], broccoli [145], hop [18], cabbage [124], and blueberries [124].…”

“…The following list gives an enumeration of all the measures or procedures investigated: Grafting [136], time of harvest [130,137], storage [146], maturity [130], wine ageing [147], geographical origin [144,147], authentication [133], juice and nectar production [129], distribution in fruit [142,143], thermal treatment [5,148], cold-pressing of essential oils [144], extraction procedures [85,142], and recovery from waste [85].…”

“…The peel of Greek Navel oranges (Citrus sinensis) is considered to be a food additive of natural origin or a pharmaceutical supplement with antioxidative properties [142] because of its polymethoxylated flavones, C-glycosylated flavones, O-glycosylated flavones and flavanones. With regard to the C-glycosylated flavones three compounds were identified, 6-Cb-glucosyldiosmin, 6,8-di-C-glucopyranosylapigenin and 6,8-di-C-b-glucosyldiosmin.…”

“…Plums [131,178], sorghum [88], potatoes [76,124], mangos [124,179,180], kernels [138], cherries [13, 42,43,181], spinach [124,156,182], kale [183], broccoli [124,145], cabbage [55], asparagus [156], lettuces [124], oranges [124], arugulas [137], tea [184], artichokes [132], coffee [185], honey [133,186], apricots [187], citrus fruits [136], oranges [142], bush butter fruits [188], radishes [156,189], cabbages [156,124], pepper [156], olive oil [85,190], cowpeas [104], cactus pears [191], Kancolla seeds [192], Pinto beans [193], beans [82], soybeans [99], and lentils [82].…”