Citrus aurantium L. var. amara Engl. (CAVA) was traditionally used as an edible and medicinal material in China. Total flavonoids (CAVAF), alkaloids (CAVAA), polysaccharides (CAVAP), coumarins (CAVAC), and neroli (CAVAO) were extracted from CAVA. Hesperidin, naringin, and neohesperidin composed 83.94% of CAVAF, and synephrine represented 50.56% of CAVAA. On the basis of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH•), 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radical cation (ABTS• +), hydroxyl radical (•OH), ferric-reducing antioxidant power (FRAP), and reducing power assays, the antioxidant activities of five components were comprehensively and comparatively investigated. CAVAF had a stronger DPPH• scavenging effect and FRAP and reducing power. CAVAP and CAVAA exhibited comparable •OH scavenging effects to vitamin C. CAVAA showed the highest ABTS• + scavenging activity. In conclusion, different constituents varied significantly toward different sources of free radicals and other oxidants. It is obvious that CAVA has various antioxidant effects, which are attributed to different components.
Keywords: Citrus aurantium L. var. amara Engl.; alkaloids; antioxidant; essential oils; flavonoids; polysaccharides.