The production of red oranges (Citrus sinensis varieties: Moro, Tarocco and Sanguinello), also known as ?pigmented? or ?blood? oranges, is almost exclusive to the Etna volcano area of Sicily, Italy. These orange cultivars developed a particular pool of antioxidant compounds that act as a protective system for the fruit against extreme day-night thermal excursion due to the volcanic soil.
Sicilian red oranges provide numerous bioactive substances that may improve health as an important key point of the so-called Mediterranean diet, especially in the prevention of free radical production and associated pathologies.
Particularly, Sicilian red oranges, as well as their fresh juices with respect to blonde cultivars, are characterised by higher levels (up to 40 per cent) of vitamin C and red anthocyanidin pigments. In addition, the fruits contain a higher content of other antioxidants, such as flavones (hesperedin, narirutin)1 and hydroxycinnamic acids (caffeic, cumaric, ferulic and sinapic).2
Cyanidin-3-O-b-glycoside (C3G) and delphinidin-3-glucoside, whose metabolism and bioavailability from red oranges juice has been demonstrated,3,4 are the main anthocyanins present in juice of pigmented oranges and responsible for their red brilliant colour.5
Antioxidant activity, antimutagenicity and the ability to contrast development of cancer and other pathologies have been demonstrated in a growing number of in vivo and in vitro studies on C3G as well as on C3G-rich food sources.6,7,8
In addition, other studies suggest that C3G has biological properties that make it helpful with gastric protective effects,9 protection against oxidative damage in human erythrocytes,10 protection against human ocular diseases,11 prevention of obesity and amelioration of hyperglycaemia in mice,12 improvement of vascular endothelial integrity,13 and prevention of inflammatory diseases.14
Red oranges also contain ample amounts of minerals and vitamins such as A, B1, B2 and also B9, which, in adequate amounts and along with folic acid, is able to reduce the risk of certain birth defects. The contemporaneous presence of high levels of potassium and the very low content of sodium makes these fruits important in contrasting arterial hypertension. Their sugars (saccharose, glucose and fructose) are rapidly assimilated, thus being useful in case of stress or tiredness.
Thanks to their low-fat content, red oranges are hypocaloric fruits: 34kcal/100g edible portion, and so they may help fight heart disease. The fibre of white callus under the peel regulates sugar, fat and protein absorption and favours intestinal transit, thus reducing putrefactive phenomena.
The citric acid lowers the acidity of the fruits and juices, so it protects ascorbic acid from oxidation and lowers urinary pH, thus preventing the formation of renal calculi.
A pharmaceutical-grade product called ROC (Red Orange Complex), a standardised extract obtained from juice of red oranges,15 has been shown to have efficacy in reducing free radical damage in humans with low antioxidant capability: smokers,16 diabetics17 and professional sportsmen.15
Very recently, cyanidin-3-glucoside and delphinidin-3-glucoside have been demonstrated to be insulin secretagogues, thus having also antidiabetic properties.La Fauci L and Galvano F, University of Reggio Calabria, Italy; Galvano G and Lazzarino G, University of Catania, Italy; De Lorenzo A, University of Tor Vergata, Italy.
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1. Manach C, et al. Bioavailability in humans of the flavanones hesperidin and narirutin after the ingestion of two doses of orange juice. Eur J Clin Nutr 2003; 572:235-42.
2. Rapisarda P, et al. Hydroxycinnamic acids as markers of Italian blood orange juices. J Agric Food Chem 1998; 462:464-70.
3. Tsuda T, et al. Absorption and metabolism of cyanidin 3-O-beta-D-glycoside in rats. FEBS Lett 1999; 449(2-3):179-82.
4. Miyazawa T, et al. Direct intestinal absorption of red fruit anthocyanins, cyanidin-3-glycoside and cyanidin-3,5-diglycoside, into rats and humans. J Agric Food Chem 1999; 47(3):1083-91.
5. Proteggente AR, et al. The compositional characterisation and antioxidant activity of fresh juices from Sicilian sweet orange Citrus sinensis L. Osbeck varieties. Free Radic Res 2003; 37(6): 681-7.
6. Rapisarda P, et al. Antioxidant effectiveness as influenced by phenolic content of fresh orange juices. J Agric Food Chem 1999; 47(11): 4718-23.
7. Serafino A, et al. Differentiation of human melanoma cells induced by cyanidin-3-O-beta-glucopyranoside. FASEB J 2004; 27 [e-pub ahead of print].
8. Meiers S, et al. The anthocyanidins cyanidin and delphinidin are potent inhibitors of the epidermal growth-factor receptor. J Agric Food Chem 2001; 492:958-62.
9. Barzaghi N, et al. Protective effect of cyanidin IdB 1027 against aspirin-induced fall in gastric transmucosal potential difference in normal subjects. Ital J Gastroenterol 1991; 235:249-252.
10. Amorini AM, et al. Cyanidin-3-O-beta-glucopyranoside protects myocardium and erythrocytes from oxygen radical-mediated damages. Free Radic Res 2003; 374:453-60.
11. Matsumoto H, et al. Stimulatory effect of cyanidin 3-glycosides on the regeneration of rhodopsin. J Agric Food Chem 2003; 5112:3560-3.
12. Tsuda T, et al. Dietary Cyanidin 3-O-?-D-glucoside-rich purple corn color prevents obesity and ameliorates hyperglycemia in mice. J Nutr 2003; 133:2125-30.
13. Xu JW, et al. Upregulation of endothelial nitric oxide synthase by cyanidin-3-glucoside, a typical anthocyanin pigment. Hypertension 2004; 442:217-22.
14. Tsuda T, et al. Cyanidin 3-O-beta-D-glucoside suppresses nitric oxide production during a zymosan treatment in rats. J Nutr Sci Vitaminol Tokyo 2002; 484:305-10.
15. Bonina F, et al. Propriet? salutistiche delle arance rosse di Sicilia: un elisir dell?Etna. L?Integratore Nutrizionale 2002; 4:7-15.
16. Comelli U, et al. Attivit? antiossidante del R.O.C. Red Orange Complex. Progress in Nutrition 2000; 1:21-27.
17. Bonina F, et al. Evaluation of oxidative stress in diabetic patients after supplementation with a standardised red orange extract. Diab Nutr Metab 2002; 15(1):14-9.