Antioxidative effects of cactus pear (Opuntia ficus indica, L. Mill.) fruits from Sicily and bioavailability of betalain components in healthy humans

Abstract

Aerobic life is characterised by a steady formation of pro-oxidants, which is approximately balanced by antioxidant defense systems. When cell’s capacity to protect itself fails, oxidative stress occurs. Because of bioactive components vegetables are now considered helpful in preventing chronic pathologies in which oxidative damage is an important etiologic factor. Cactus pear (Opuntia ficus-indica) fruit contains substantial amounts of vitamin C, biothiols, and taurine, and redox-active betalain pigments. It has been shown that a short-term supplementation (500 g fruit pulp daily, 2 wk) positively affected the body’s redox balance, decreased lipid oxidation, and improved antioxidant status of healthy humans. Supplementation with vitamin C at a comparable dosage enhanced overall antioxidant defence but did not affect body oxidative stress. Oral administration of a water-soluble extract from the fresh fruit pulp resulted in a remarkable anti-inflammatory effect in rats. Betanin and indicaxanthin may be considered as contributors to the fruit effects. Both compounds behave as scavengers of biologically relevant radicals, and antioxidants in various experimental sets in vitro and ex vivo, or may affect redox-sensitive cell transduction pathways in cultured cells. Moreover both are bioavailable. Kinetic studies in healthy humans showed a plasma peak of the micromolar order at 3 h, after a single ingestion of 500 g cactus pear fruit pulp, providing 28 mg and 16 mg indicaxanthin and betanin, respectively. The urinary disposal of indicaxanthin and betanin over 12 h represented 76 % and 3.7 %, respectively, of the ingested compounds. Circulating low density lipoproteins and red blood cells incorporated both betalains time-dependently, in parallel with their plasma concentration, and exhibited enhanced resistance to an ex-vivo-induced oxidation, the higher the amount of betalains the higher the resistance. Because its bioactive phytochemicals, cactus pear may have an important role in health promotion.