Chemical Constituents and Antioxidant Activity of Citrus paradisi (Star-ruby Red Grapefruit) and Citrus sinensis (Blood Sweet Orange) Egyptian Cultivars

Abstract

Eleven known coumarins: osthol, xanthotoxin, bergapten, isopimpinellin, scoparone, limettin, aurapten, auraptene, scopoletin, bergaptol and umbelliferone were isolated for the first time from n-hexane fraction of peels of star ruby red grapefruit Egyptian cultivar, while only six coumarins: isoimpratorin, osthol, bergapten, scoparone, limettin and bergaptol were isolated from n-hexane fraction of peels of blood sweet orange Egyptian cultivar. In addition, two steroids: β-sitosterol and stigmasterol were isolated from both plants. Three flavonoid glycosides were isolated from n-butanol fraction of star-ruby red grapefruit: poncirin, neohesperidin and naringin, whereas didymin, hesperidin and narirutin were isolated from blood sweet orange n-butanol fraction. Nobiletin and tangeretin were isolated from the dichloromethane fractions in both plants. The volatile oils of peels of star-ruby red grapefruit and blood-sweet orange cultivars were analyzed by GC/Mass. Limonene was identified as the major constituent in both Citrus species: 46 and 92% respectively. Study of the antioxidant activity of different extracts of both Citrus cultivars revealed that the alcoholic extracts of both cultivars showed the highest antioxidant activity.