Cactus pear fruit improves oxidative stress

Nutrition Research Newsletter, Oct, 2004

Increased consumption of fruits and vegetables is associated with protection against various pathologies, in which oxidative damage is an important etiologic factor. On the basis of the assumption that antioxidant components of fruit and vegetables may be responsible for the effects of such food, many studies have focused on vitamin C and carotenoids. However, the results of supplementation studies with pure vitamins are not conclusive about their contribution to the protection of health. Other antioxidant components, such as polyphenolic pigments, have received considerable attention in the past decade. Most fruit contain antioxidant vitamins and one or more polyphenolic compounds.

The cactus pear is a common vegetation in Mexico, much of Latin America, South Africa, and the Mediterranean. A recent study showed that the aqueous extracts of this fruit possess a high total antioxidant capacity. Cactus pear fruit contains vitamin C and two characteristic betalain pigments, the radical-scavenging properties and antioxidant activities of which have been shown in vitro. Therefore, a group of Italian researchers investigated the effects of short-term supplementation with cactus pear fruit compared with vitamin C on biomarkers of oxidative stress and plasma antioxidant status in healthy humans.

Eighteen healthy subjects were recruited for this study. The subjects were randomly divided into two groups, which were assigned to supplementation with either 250 g cactus pear pulp or 75 mg vitamin C at each of the two main daily meals for two weeks. After a six-week washout period, each group received the other treatment. Before (baseline) and after each treatment, 8-epiprostaglanding F2 (8-epi-PGF2) and malondialdehyde in plasma, the ratio of reduced to oxidized glutathione (GSH:GSSG) in erythrocytes, and lipid hydroperoxides in LDL were measured as biomarkers of oxidative stress; plasma Trolox-equivalent antioxidant activity (TEAC) and vitamins A, E and C were evaluated as well as indexes of antioxidant status.

Both treatments caused comparable increases compared with baseline in plasma concentrations of vitamins E and C. Vitamin A and TEAC did not change significantly. After supplementation with cactus pear fruit, 8-epi-PGF2 and malondialdehyde decreased by approximately 30% and 75%, respectively. Supplementation with cactus pear enhanced concentration of GSH and decreased concentration of GSSG in red blood cells, resulting in a higher GSH:GSSG LDL hydroperoxides were reduced by almost one-half. Supplementation with vitamin C, at least a dosage comparable with that provided by the cactus pear fruit, did not significantly affect any marker of oxidative stress.

The results show that daily supplementation with 500 g cactus pear fruit pulp for two weeks positively affects the body's redox balance, decreases oxidative damage to lipids, and improves antioxidant status in healthy humans. Therefore, this data suggest that something in the cactus pear fruit other than vitamin C may help to decrease lipid oxidation. Betanin and indicaxanthin, the characteristic pigments of the fruit, may be considered. However, antioxidant or other biological activities of betalains in vivo deserve to be more deeply investigated.

Luisa Tesoriere, Daniela Butera, Anna Maria Pintaudi, et al., Supplementation with cactus pear (Opuntia ficus-indica) fruit decreases oxidative stress in healthy humans: a comparative study with vitamin C, Am J Clin Nutr 80:391-395 (August 2004) [Address reprint requests to MA Livrea, Dipartimento Farmacochimico Tossicologico e Biologico, Via C Forlanini, 1 90134 Palermo, Italy. E-mail: ma196@unipa.it]