Antioxidant Activities of Sicilian Prickly Pear (Opuntia ficus indica) Fruit Extracts and Reducing Properties of Its Betalains:  Betanin and Indicaxanthin

Abstract

Sicilian cultivars of prickly pear (Opuntia ficus indica) produce yellow, red, and white fruits, due to the combination of two betalain pigments, the purple-red betanin and the yellow-orange indicaxanthin. The betalain distribution in the three cultivars and the antioxidant activities of methanolic extracts from edible pulp were investigated. In addition, the reducing capacity of purified betanin and indicaxanthin was measured. According to a spectrophotometric analysis, the yellow cultivar exhibited the highest amount of betalains, followed by the red and white ones. Indicaxanthin accounted for about 99% of betalains in the white fruit, while the ratio of betanin to indicaxanthin varied from 1:8 (w:w) in the yellow fruit to 2:1 (w:w) in the red one. Polyphenol pigments were negligible components only in the red fruit. When measured as 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) equivalents per gram of pulp, the methanolic fruit extracts showed a marked antioxidant activity. Vitamin C did not account for more than 40% of the measured activity. In addition, the extracts dose-dependently inhibited the organic hydroperoxide-stimulated red cell membrane lipid oxidation, as well as the metal-dependent and -independent low-density lipoprotein oxidation. The extract from the white fruit showed the highest protection in all models of lipid oxidation. Purified betanin and indicaxanthin were more effective than Trolox at scavenging the [2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)] diammonium salt cation radical. Cyclic voltammetric measurements show two anodic waves for betanin and indicaxanthin, and differential pulse voltammetry shows three anodic waves for betanin, with calculated peak potentials of 404, 616, and 998 mV, and two anodic waves for indicaxanthin, with peak potentials of 611 and 895 mV. Betanin underwent complex formation through chelation with Cu 2+ , whereas indicaxanthin was not modified. These findings suggest that the above betalains contribute to the antioxidant activity of prickly pear fruits.KEYWORDS: Betalains; natural antioxidants; low-density lipoprotein; prickly pear; betanin; indicaxanthin INTRODUCTIONEvidence continues to emerge suggesting that components of fruits and vegetables may be protective against oxidative damage (1-3). In addition to antioxidant vitamins and minerals, polyphenols and other non-nutrient compounds of vegetables and fruits have been recognized as potential factors which can be beneficial to human health (4-6). The prickly pear (Opuntia ficus indica) is a member of the Cactaceae family and is widely distributed in Mexico, much of Latin America, South Africa, and the Mediterranean area. The nutritional properties of the fresh stems (cladodes) have long been known, and prickly pear is used also in traditional medicine for its hypoglycemic and hypolipidemic actions (7-9). In the industrialized countries of the Mediterranean area, cladodes are not a usual nutritional source for humans, but the fruits are largely consumed. Sicily ranks second am...

Biothiols, Taurine, and Lipid-Soluble Antioxidants in the Edible Pulp of Sicilian Cactus Pear (Opuntia ficus-indica) Fruits and Changes of Bioactive Juice Components upon Industrial Processing

“…Beside nutrients such as sugars, vitamins, and minerals (7-9), they contain high amounts of betalains, natural pigments widely used as safe colorants for foods and cosmetics (9)(10)(11)(12)(13)(14). In addition, recent studies focusing on the antioxidant potential of these fruits provided evidence of novel functional aspects (9,10). Betalains, the reducing and radical-scavenging activity of which have been demonstrated in various in-vitro and ex-vivo experiments (9,(15)(16)(17)35), as well as vitamin C have appeared as important contributors to the total antioxidant activity of cactus pear fruits (9).…”

“…Significant amounts of vitamin C are present (8)(9)(10). In addition, the fruits proved to be a rich source of betalain pigments, either betaxanthins or betacyanins (9)(10)(11)(12)(13)(14), the redox properties and antioxidant activity of which have recently been demonstrated (9,15,17). Other compounds can be considered to provide more complete information about the antioxidant potential of the cactus pear fruits.…”

Anti-proliferative and pro-apoptotic activity of whole extract and isolated indicaxanthin from Opuntia ficus-indica associated with re-activation of the onco-suppressor p16INK4a gene in human colorectal carcinoma (Caco-2) cells

“…Aqueous extract from O. ficus-indica fruits (yellow cultivar) was prepared as described [12], and Ind isolated from the extract and quantified as reported [12,24].…”

“…Ind is a redox-active compound [12], we then investigated whether its anti-proliferative activity was associated with oxidative unbalance. With respect to untreated cells, neither the level of intracellular ROS nor total thiols, as a measure of the global cell redox state, appeared significantly modified by 115 lM Ind within 6-48 h of incubation (Fig.…”

“…We showed that this betaxanthin behaves as a radical scavenger and antioxidant [12][13][14], interacts with and locates in membranes [15,16], and affects cell redox-sensitive signaling pathways [17,18]. When consuming cactus pear fruits, Ind is stable at the digestive conditions, not metabolized by the enterocytes, and highly bioavailable in humans in its native form [19][20][21].…”