Journal of Applied Botany and Food Quality 91, 211 - 218 (2018), DOI:10.5073/JABFQ.2018.091.028 1*Instituto de Horticultura, Universidad Autónoma Chapingo, Carretera México-Texcoco, Chapingo, Estado de México, México 2Instituto de Alimentos, Universidad Autónoma Chapingo, Carretera México-Texcoco, Chapingo, Estado de México, México 3Tecnológico Nacional de México, Instituto Tecnológico de Conkal, Avenida Tecnológico s/n Conkal, Yucatán, México Nutraceutical components, antioxidant activity, and color of 11 varieties of prickly pear (Opuntia sp.) M. Ramírez-Ramos1, K. Medina-Dzul3, R. García-Mateos1*, J. Corrales-García2, C. Ybarra-Moncada2, A.M. Castillo-González1 (Submitted: October 13, 2017; Accepted: June 26, 2018) * Corresponding author Summary In Mexico, there are 50 recorded varieties of the prickly pear fruit. National production covers only the white-pulp fruit, but other red varieties have export potential; however, their nutraceutical properties are unknown. The pulp and peel (underutilized tissue) of the pigmented fruits of the genus Opuntia sp. are marketed on a limited basis. They represent an alternative source of stable pigments (betalains), which are associated with antioxidant properties, for the agroindustry. The objective was to assess the content of nutra- ceutical components, antioxidant activity, and peel and pulp color of 11 varieties of the prickly pear fruit that are marketed on a small scale. Statistical analysis revealed that Roja Villanueva peel had the highest betalain content (39.97 mg 100 g-1 FW). Alteña Blanca peel demonstrated the highest concentration of phenolic compounds (618.39 mg GAE 100 g-1 FW), whereas Alteña Roja had the highest ascorbic acid content (37.14 mg AAE 100 g-1 FW). The greatest nutraceutical potential was observed in the pulp of the non-marketed Tzaponopal Rojo variety of the species O. robusta var. larreyi, due to the high antioxidant activity (0.0183 mg mL-1), as well as the darkest color (‹ hue value, 12.31) and the lowest lightness (‹ luminosity, 19.31), which coincides with the highest betalain concentration. Keywords: antioxidant components, betalains, pulp, peel. Introduction Mexico is considered the center of origin of the family Cactaceae, which includes approximately 1500 species of the genus Opuntia (ANOOP et al., 2012), both wild and cultivated (SÁENZ, 2006). The subgenera Opuntia and Nopalea are the main producers of the edible fruit known as prickly pear fruit, grouped by its pigmentation into purple, red, orange, yellow, and white fruit (SEGURA et al., 2007; CARUSO et al., 2010). Prickly pear grows in arid and desert regions. It has a photosynthetic metabolism of Crassulacean type called crassulacean acid metabolism (CAM), which allows the production of biomass in the arid and drought conditions characteristic of its habitat (ANDREU et al., 2017). During the photosynthetic process, CAM plants open their stomata during the desert nights and close them during the hot, dry days, thus efficiently using night moisture (TAIZ and ZEIGER, 2002). In Mexico, white-pulp and green-peel prickly pears are highly appreciated for their market value. In 2014, prickly pear produc- tion in the country reached approximately 588 000 t (SIAP, 2014); however, despite the great production and variability of this fruit in the country, the levels of antioxidant components in most prickly pear species are unknown. Nonetheless, these components in vari- ous other fruits are known to provide important nutraceutical benefits to consumers (TSAO and AKHTAR, 2005; ANOOP et al., 2012). Consumption of these other fruits prevents some chronic-degenera- tive diseases, due to the presence of certain metabolites (phenolic compounds, flavonoids, ascorbic acid, and betalains) (SUMAYA- MARTÍNEZ et al., 2011; ABOU-ELELLA and ALI, 2014). Biosynthetically, betalamic acid-derived betalains, which are pigments used in the agri-food industry as natural colorants (STRACK et al., 2003), also have antioxidant properties (LIVREA and TESORIERE, 2006; ALBANO et al., 2015). Moreover, color is part of fruit quality and may therefore be a factor in its preference, acceptance, or rejection, and play a decisive role in the failure or success of prickly pear marketing. The wide genetic diversity of the Mexican prickly pear justifies the study of nutraceutical content, particularly in pigmented prickly pear varieties. The objective of the present study was to assess the content of nutraceutical components, antioxidant activity, and pulp and peel color of 11 varieties of prickly pear marketed on a small scale, and to identify those with the greatest nutraceutical attributes. Such nutraceutical information will be of benefit to consumers. Material and methods Plant material collection Healthy and pest-free fruits were harvested in the Dr. Facundo Barrientos Pérez Experimental Station at the Universidad Autó- noma Chapingo in Chapingo, State of Mexico (Tab. 1), located at 19º 29́ N and 98º 53́ W, at an altitude of 2240 m. The climate is C (Wo) (w) b (i’) g, considered the driest of the subhumid climates, with summer rains and mild temperatures. The area has a mean annual temperature of 17.8 °C and rainfall of 644.8 mm per year. The harvest criteria were the visual parameters used commercially in the producing region for each variety (completely characteristically developed fruit, with fruit weight ranging from 125 g to 230 g, depending on the variety) (CORRALES et al., 2006). After cutting, fruits were stored for 15 days. The pulp was then separated from the seed and peel, and the tissue (pulp and peel) was fractionated into small portions and frozen by direct immersion in liquid nitrogen. The samples were then stored at -20 ± 2 °C for later analysis. Quantification of total betalains (betacyanins and betaxanthins) Pigment content was determined according to the methodology described by CASTELLANOS-SANTIAGO and YAHIA (2008). The frozen sample (1 g) was mixed with 10 mL distilled water, sub- jected to sonication for 20 min, and centrifuged at 2200 g for 20 min. Absorbance of the extracts was measured in a Genesys 10S spectrophotometer (Thermo Scientific, Florida, USA) at 483 nm (betaxanthins) and 538 nm (betacyanins). In order to estimate the pigment concentration, the following equation was used: betacyanins or betaxanthins (mg g-1 FW) = (A × DF × MW × V) (ε × l × FW)-1, where A = absorbance; DF = dilution factor; MW = molecular weight (betacyanin: 550 g mol-1, betaxanthin: 308 g mol-1); V = extract 212 M. Ramírez-Ramos, K. Medina-Dzul, R. García-Mateos, J. Corrales-García, C. Ybarra-Moncada, A.M. Castillo-González volume (mL); ε = molar extinction coefficient (betacyanin: 60 000 L mol cm-1; betaxanthin: 48 000 L mol cm-1); FW = fresh sample weight (g); and l = cell length (1 cm). Total betalain content was expressed as mg per 100 g fresh weight (FW). Extraction of total phenolic compounds and flavonoids The sample (1 g) was dissolved in 25 mL ethanol (95% v/v) in an ultrasonic bath (Cole-Parmer 8892, Illinois, USA) for 15 min. After 24 h, the volume was brought to 25 mL with ethanol (80% v/v) and centrifuged at 1409 g. This extract was subsequently used to determine the content of total phenolic compounds and flavonoids. Quantification of total phenolic compounds The method proposed by WATERMAN and MOLE (1994) was fol- lowed. First, 10 mL Na2CO3 (10% w/v) were added to 0.5 mL ethanolic extract, and the mixture was then incubated at 38 °C for 15 min. Subsequently, 3 mL water and 1 mL Folin-Ciocalteu reagent:water (1:1 v/v) were added to 1 mL of this mixture, which was left to stand for 15 min in the dark, and absorbance was then measured at 760 nm in a Genesys 10S spectrophotometer. Total phenolic compound content in the extract was expressed as mg gallic acid equivalents per 100 g fresh weight (mg GAE 100 g-1 FW). Quantification of flavonoids Flavonoid content was quantified according to the method proposed by CHANG et al. (2002). First, 1.5 mL ethanol (95% v/v), 0.1 mL AlCl3 (10% w/v), 0.1 mL 1 M potassium acetate, and 2.8 mL distilled water were added to 0.5 mL ethanolic extract. The mixture remained at room temperature for 30 min, and absorbance was measured in a Genesys 10S spectrophotometer at 415 nm. Results were expressed as mg quercetin equivalents per 100 g fresh weight (mg QE 100 g-1 FW). Quantification of ascorbic acid The sample (1 g) was homogenized in 3 mL metaphosphoric acid (3% v/v) for 3 min. The mixture was filtered, and 1 mL supernatant was brought to 10 mL with metaphosphoric acid (3% v/v). Then 2 mL pH 4 buffer solution (glacial acetic acid:sodium acetate [5% w/v, 1:1]), 3 mL dichloroindophenol, and 15 mL xylene were added to 2 mL of the mixture, which was shaken vigorously in a vortex (Thermolyne Type 6700, USA). Absorbance was measured in a spectrophotometer at 520 nm. Ascorbic acid was calculated with the following equation: mg total ascorbic acid = (C × V × 100) / (A × W), where C = ascorbic acid in the sample; V = capacity volume; A = aliquot of the solution taken (mL); and W = sample weight or volume. Results were expressed as mg ascorbic acid equivalents per 100 g fresh weight (mg AAE 100 g-1 FW). Antioxidant activity assessment The analysis was performed using the DPPH (2, 2-diphenyl-1- picrylhydrazyl, Sigma-Aldrich) free radical method described by AMICO et al. (2008). For analysis, 10 g of sample were macerated in methanol and subjected to sonication for 20 min. The mixture was filtered, and the supernatant was concentrated in a Büchi R-210 rotary evaporator (Flawil, Switzerland). From the methanol extract, the following solutions were prepared in methanol by serial dilution to obtain 0.2, 0.15, 0.1, and 0.05 mg mL-1 concentrations. As references, 0.1, 0.001, and 0.0001 mg mL-1 concentrations of quercetin and ascorbic acid were individually prepared. Next, 3 mL DPPH solution (0.1 mM) were added to 1 mL of each concentration of extracts and the individual references. Mixtures were left at room temperature for 30 min, and then absorbance readings were taken at 516 nm. DPPH percentage was determined by the following formula: % DPPH = (Ablank − Asample) × 100 / Ablank, where Ablank is the control absorbance (DPPH 0.1 mM) and Asample is the absorbance obtained for each sample after 30 min with DPPH 0.1 mM. The antioxidant activity of the samples was determined by calculating the mean inhibitory concentration (IC50), which is the concentration required by the sample to decrease DPPH absorbance to 50%. Low absorbance of the reaction mixture indicated high antioxidant activity. The standard curve was built with 3.93 mg DPPH dissolved in 100 mL methanol to obtain a 0.1 mM concentration (stock solution). The following concentrations were prepared from this solution: 0.01, 0.02, 0.04, 0.06, 0.08, and 0.1 mM DPPH. Absorbance was measured at 516 nm in a Genesys 10S spectrophotometer, and readings were taken in triplicate; methanol was used as a blank. Tab. 1: Descriptions of 11 varieties and species of prickly pear (Opuntia sp.) grown at the Universidad Autónoma Chapingo Experimental Station, Chapingo, Mexico. Species Variety Origin Color Market value* Opuntia sp. Alteña Blanca Celaya, Gto. Yellow-greenish LMP Opuntia sp. Alteña Roja Celaya, Gto. Orange AMP O. ficus-indica (L.). Mill Huatusco Huatusco, Ver. Yellow LMP O. ficus-indica (L.). Mill Solferino Chapingo, Méx. Orange AMP O. ficus-indica (L.). Mill Roja Villanueva Villanueva, Pue. Orange AMP O. ficus-indica (L.). Mill Jade Desconocido Pink LMP O. ficus-indica (L.). Mill Copena CEII Zacatecas, Zac. Pink AMP O. ficus-indica (L.). Mill Copena VI Chapingo, Méx. Red - purple LMP O. megacantha Salm Morada San Martín de las Pirámides, Méx. Red AMPP O. megacantha Salm Plátano Ojuelos, Jal. Yellow LMP O. robusta var. Larreyi Tzaponopal Rojo San Martín de las Pirámides, Méx. Red AMP *LMP: low market potential; AMP: average market potential; AMPP: average market potential as a source of pigments (CORRALES-GARCÍA and HERNÁNDEZ- SILVA, 2005). Nutraceutical components of prickly pear (Opuntia sp.) 213 Measurement of color parameters Pulp and peel color were determined by assessing lightness (L), tone angle (hue) and purity of color or chromaticity index (chroma) with a HunterLab colorimeter (MiniScan XE Plus 45/ 0-L, Reston, Virginia, USA). Readings from a* and b* were obtained to clearly quantify color differences among the tissues and varieties. Variables were calculated with the following equations: hue = tan-1 (a/b) and chroma = (a2 + b2) ½ (MC GUIRE, 1992). Statistical analysis An asymmetric 11 × 2 factorial design, in which the pulp or peel of each variety was considered as a treatment, was used, with four replications. Results were analyzed using an analysis of variance and Tukey’s range test (P ≤ 0.05). The least significant difference (LSD) (α = 0.05) and principal component analysis were obtained with the SAS (Statistical Analysis System 9.0). Results and discussion Total betalain content (betacyanins and betaxanthins) Total betalain concentration was higher in red prickly pear fruits than in white and orange ones, which showed lower concentrations in pulp and peel (Tab. 2). The total betalain levels (92.08 mg 100 g-1 FW) in the pulp of the Tzaponopal Rojo variety surpassed those of the other varieties. KUTI (2005) reported a betalain concentration in Opuntia spp. fruits similar to that found in the present research (81.5 mg 100 g-1 FW). Betalains are responsible for the array of fruit colors in the many species and varieties of the genus Opuntia (STINTZING and CARLE, 2007). These metabolites derive biosynthetically from betalamic acid and are categorized as either betacyanins or betaxanthins. Betacyanins are red-purple, and beta- xanthins are responsible for the orange-yellow color of the pulp and rind of these fruits (ZRŸD and CHRISTINET, 2004; STINTZING and CARLE, 2007). The Alteña Blanca variety (yellow-green color) had the lowest content of betacyanins (responsible for red-purple color) and betaxanthins (responsible for yellow-orange color) in both pulp and peel; by contrast, the highest betacyanin content was found in the pulp of the Tzaponopal Rojo (red), Copena VI (red-purple), and Jade (pink) varieties. The highest betaxanthin content was found in the peel of Roja Villanueva and the pulp of Tzaponopal Rojo. These results support the view that the high content of pigments in the pulp and peel of these varieties might make them good sources of natural pigments for use in the food industry. Values for both pigments found in the present study (0.46 mg - 49 mg 100 g-1 FW for betacyanins and 0.5 mg -19.91 mg 100 g-1 FW for betaxanthins) were superior to those found by LÓPEZ et al. (2015) for the Cambray genotype “xoconostle” (sour prickly pear fruit), which had values of 26.05 mg 100 g-1 FW Tab. 2: Content of total betalains, betacyanins, and betaxanthins in the fruit of 11 varieties and species of prickly pear (Opuntia sp.) harvested at the Universidad Autónoma Chapingo Experimental Station, Chapingo, Mexico. Species Variety Tissue* Total betalains Betacyanins Betaxanthins (mg 100 g-1 FW) (mg 100 g-1 FW) (mg 100 g-1 FW) Opuntia sp. Alteña Blanca Peel 0.99k 0.50g 0.50h Pulp 1.03k 0.46g 0.57h Opuntia sp. Alteña Roja Peel 19.20hj 12.46ed 6.74dg Pulp 23.08gi 14.36cd 8.73cf O. ficus indica Huatusco Peel 4.25jk 2.24eg 2.01gh Pulp 4.34jk 1.81fg 2.53gh O. ficus indica Solferino Peel 22.98gi 15.24cd 7.74dg Pulp 19.08hj 11.35df 7.74dg O. ficus indica Roja Villanueva Peel 39.97cg 23.97bc 16.01ab Pulp 35.30be 20.62bd 14.67ac O. ficus indica Jade Peel 21.21ih 14.89cd 6.42eh Pulp 41.91bc 30.13b 11.79be O. ficus indica Copena CEII Peel 31.57eh 21.78bc 9.79cf Pulp 40.36bd 29.04b 11.32be O. ficus indica Copena VI Peel 38.85dg 27.14b 11.71be Pulp 43.73b 30.91b 12.82bd O. megacantha Morada Peel 17.03hk 12.67ed 4.36fh Pulp 27.86fi 20.37bd 7.49dg O. megacantha Plátano Peel 14.02ik 2.19efg 11.83be Pulp 11.48ik 1.54fg 9.95bf O.robusta/Larreyi Tzaponopal Rojo Peel 33.41eh 23.50bc 9.90bf Pulp 69.06a 49.15a 19.91a CV 21.62 23.89 26.27 *Fresh weight; CV = Coefficient of variation. Means with the same letters in a column are not significantly different (Tukey, P ≤ 0.05). 214 M. Ramírez-Ramos, K. Medina-Dzul, R. García-Mateos, J. Corrales-García, C. Ybarra-Moncada, A.M. Castillo-González for betacyanins and 9.01 mg 100 g-1 FW for betaxanthins. KHATABI et al. (2016) demonstrated that differences in betalain content in the juice and pulp of prickly pear fruits could be attributed to variability in prickly pear ecotypes, physiologies, and growth conditions. Pigments identified in prickly pear (Opuntia) fruits are stable, while the betacyanins in pitaya (Stenocereus pruinosus) tend to decompose rapidly when they are isolated from the fruit (STINTZING and CARLE, 2007). Nevertheless, the rate of degradation of the pigments in Opuntia and Stenocereus fruits is unknown. These pigments exhibit important antioxidant activity and are non-toxic to humans (SUMAYA-MARTÍNEZ et al., 2011). Moreover, high levels of betalains help prevent cancer and lipid oxidation of membranes (LIVREA and TESORIERE, 2006). Additionally, fruit quality is based partly on color, which may be a factor in its preference, acceptance, or rejection, thus playing a decisive role in the failure or success of prickly pear marketing. Total phenolic compound content Phenolic compounds are another group of secondary metabolites, identified in some fruits of the Opuntia genus (PIMIENTA-BARRIOS et al., 2008; OSORIO-ESQUIVEL et al., 2011; ANDREU et al., 2017; MENA et al., 2018), that protects plants from oxidative stress, and their consumption contributes to preventing disease in humans. It is important to point out that in every variety, phenolic compound levels were much higher in the peel than in the pulp; this is consistent with the work of MOUSSA-AYOUB et al. (2011), who observed similar behavior in O. macrorhiza fruits. Alteña Blanca peel had the highest concentration of these metabolites (618.39 mg GAE 100 g-1 FW); on the other hand, Copena CEII pulp had the lowest concentration (106.60 mg GAE 100 g-1 FW) (Tab. 3). Results were superior to those obtained by LÓPEZ et al. (2015) for 15 xoconostle cultivars whose phenolic compound contents ranged between 132.83 mg and 231.37 mg GAE 100 g-1 FW. YAHIA and MONDRAGÓN-JACOBO (2011) also reported total phenol values in different varieties of prickly pear (106.6 mg -130.0 mg GAE 100 g-1 FW), and concentrations of phenolic compounds measured by GARCÍA-CRUZ et al. (2013) in red pitaya (106.0 mg GAE 100 g-1 FW) were lower than those found in prickly pear fruits. The differences observed among species and varieties of different genera may be due to (a) genetic factors (MOUSSA-AYOUB et al., 2014; OSORIO- ESQUIVEL et al., 2011), and (b) stress caused by harvest and handling of fresh fruits, which alters physiology and stimulates responses that cause phenolic compounds to accumulate (PIROVANI et al., 2009). The effect of genotypic differences on the phenolic profiles of prickly pear fruits has also been investigated (MOUSSA-AYOUB et al., 2014; STINTZING et al., 2005). However, several studies point out that the concentration of phenolic compounds in prickly pear depends on the environmental conditions, as well as the part of the cactus plant under consideration (KHATABI et al., 2016; MOUSSA-AYOUB et al., 2014; STINTZING et al., 2005). There was no relationship between the content of these phyto- Tab. 3: Content of total phenolic compounds, flavonoids, and ascorbic acid in the fruit of 11 varieties and species of prickly pear (Opuntia sp.) harvested at the Universidad Autónoma Chapingo Experimental Station, Chapingo, Mexico. Species Variety Tissue* Phenolic compounds Flavonoids Ascorbic acid (mg GAE 100 g-1 FW) (mg QE 100 g-1 FW) (mg AAE 100-1 g FW) Opuntia sp. Alteña Blanca Peel 618.39ª 27.73a 2.26de Pulp 165.56ef 1.34f 3.74ce Opuntia sp. Alteña Roja Peel 486.79b 23.88ab 2.26de Pulp 120.75f 4.37df 37.14a O. ficus indica Huatusco Peel 425.58bc 20.13ab 0.56e Pulp 131.96ef 2.60ef 0e O. ficus indica Solferino Peel 404.59bc 22.41ab 6.80cd Pulp 148.6ef 3.23df 4.62ce O. ficus indica Roja Villanueva Peel 242.98ed 20.05ab 0e Pulp 118.39f 9.60ce 0e O. ficus indica Jade Peel 374.88bc 20.05ab 14.85b Pulp 122.52f 6.69df 2.80ce O. ficus indica Copena CEII Peel 322.99cd 20.74ab 0e Pulp 106.60f 8.34df 0e O. ficus indica Copena VI Peel 425.59bc 23.96ab 16.59b Pulp 143.74ef 8.23df 8.04c O. megacantha Morada Peel 389.03bc 17.76bc 0e Pulp 107.19f 6.00df 0e O. megacantha Plátano Peel 400.82bc 21.43ab 15.83b Pulp 111.90f 6.19df 15.49b O.robusta/Larrey Tzaponopal Rojo Peel 219.22ef 21.79ab 0e Pulp 161.43ef 11.21cd 0e CV 16.59 22.1 34.88 *Fresh weight; CV = Coefficient of variation. Means with the same letters in a column are not significantly different (Tukey, P ≤ 0.05). Nutraceutical components of prickly pear (Opuntia sp.) 215 chemicals and the pulp and peel colors of the different varieties studied; this behavior was also observed by SUMAYA-MARTÍNEZ et al. (2011), who point out that when investigating the fruit colors of three groups of prickly pear cultivars (purple, yellow, and white), no relationship with total phenol content was found. However, KHATABI et al. (2016) reported that the red prickly pear contains higher amounts of polyphenols than those of the yellow variety. Assessment of the phenolic profile of prickly pear has been limited. Phenolic composition of different parts of O. ficus-indica had been previously addressed (MENA et al., 2018; MOUSSA-AYOUB et al., 2014). MENA et al. (2018) identified the phytochemical profiles (41 compounds, mainly phenolics) of four botanical parts from six different prickly pear cultivars of O. ficus-indica. Results obtained in the present study suggest that the prickly pear is an important source of phenolic compounds and can be used as a functional and nutraceutical food. Its consumption could help in the prevention of some chronic or degenerative diseases (SOTO- HERNÁNDEZ et al., 2017). Flavonoid content The flavonoid concentrations in all varieties were lower than the phenolic compound content, probably due to the presence of pro- cyanidins (condensed tannins) and phenolic acids (chlorogenic acid and ferulic acid), which also occurs in other fruits (MENA et al., 2018). It is important to highlight that procyanidin content has not been studied in prickly pear. Another explanation for the loss of flavonoids may be that during the ripening of fruits these metabolites are transformed into phenolic compounds (BARZ and HOESEL, 1977). No significant differences in flavonoid content were found among varieties (Tab. 3). In all varieties, higher concentrations of these metabolites were observed in the peel than in the pulp. According to BRIELMAN et al. (2006), some types of flavonoids are responsible for the white or yellow pigmentation of some plant tissues, which agrees with the results obtained in the present study. Few studies describe the presence of flavonoids in prickly pear fruits (MOUSSA-AYOUB et al., 2011; MENA et al., 2018). These metabolites are also important as they have antioxidant, anti-inflammatory, and anticancer pro- perties (CROZIER et al., 2009). Furthermore, the results of this study can contribute knowledge of a food resource used ancestrally and still a part of the cultural identity of some states in the Mexican Republic, but with little recognized potential today. Ascorbic acid content Significant differences (P ≤ 0.05) were found in ascorbic acid content in the peel of the Plátano, Jade, and Copena VI varieties as compared to the remaining varieties (Tab. 3). In the peel of the Roja Villanueva, Morada, Copena CEII, Tzaponopal Rojo, and Huatusco varieties, no ascorbic acid was detected. Despite to the unstable structure of this metabolite in the presence of oxygen (DE ANCOS et al., 2009), its possible degradation can be ruled out because all the samples were processed simultaneously; therefore, the difference may be due to genetic factors. LATOCHA et al. (2011) point out that genotype is one of the most important factors in the identification of fruits with high ascorbic acid content. Alteña Roja pulp presented the highest ascorbic acid content (37.14 mg AAE 100 g-1 FW), which is similar to that reported by CORRAL-AGUAYO et al. (2008) (40 mg AAE 100 g-1 FW) but inferior to that reported by KUTI (2004) in O. ficus- indica fruits (45.8 mg AAE 100 g-1 FW). FIGUEROA et al. (2010) reported lower levels for the Mango (O. albicarpa) and Cacalote (O. cochinera) cultivars (5.31 mg AAE 100 g-1 FW and 25 AAE mg 100 g-1 FW, respectively). Values found in the present study support the idea that the content of this metabolite in some prickly pear varieties could contribute to antioxidant activity in consumers’ diets (ALBANO et al., 2015). Differences in ascorbic acid content reported by other authors could be attributable to crop conditions, taking into account the tolerance of prickly pear species to extreme climatic conditions, because when Opuntia species (CAM plants) are grown under limiting soil nutri- ent and water conditions, their chemical composition may change (SUMAYA-MARTÍNEZ et al., 2011). Antioxidant activity Alteña Blanca peel presented the highest antioxidant activity (lowest concentration of sample required to inhibit 50% of the DPPH radical concentration) (Fig. 1). Roja Villanueva peel had the lowest antioxidant activity. In addition, some significant differences (P ≤ 0.05) were found between the IC50 of the pulp and peel of this variety compared to that of the same tissues of the other varieties (Fig. 1). However, other methods that more completely reflect antioxidant capacity were not evaluated. Among the advantages of cultivating Opuntia fruits are the presence of antioxidant compounds and the high content of stable pigments (betalains) in the pulp and peel of some varieties (Tzaponopal Rojo, Copena CEII, and Copena VI), which are important to the food industry, and their low water requirements. These advantages make them an option for agriculture in arid and semiarid regions of the country. BRAT et al. (2007) mention that the antioxidant activity of fruits and vegetables is not only associated with phenolic compounds but is also attributed to the content of other metabolites such as vitamin C, carotenoids, and sulfur compounds; therefore, the antioxidant activity found in some varieties in the present study may be due to the possible synergistic effect of a different set of phytochemicals. ÁVILA-NAVA et al. (2014) used the DPPH method to evaluate the antioxidant activity of O. ficus-indica fruits. Healthy individuals first consumed an antioxidant-poor diet and then consumed 300 g of O. ficus-indica. At the end of the study, a significant increase in antioxidant activity in plasma and blood (20% and 5%, respectively) resulted. Fig. 1: Antioxidant activity in the fruit of 11 varieties and species of prickly pear (Opuntia sp.) harvested at the Universidad Autónoma Chapingo Experimental Station, Chapingo, Mexico. Different letters in the bars are significantly different (Tukey, P ≤ 0.05). Color parameters In most varieties, significant differences between pulp and peel lightness were observed (Tab. 4). Alteña Blanca pulp (lightest color) presented the greatest L, followed in descending order by the 216 M. Ramírez-Ramos, K. Medina-Dzul, R. García-Mateos, J. Corrales-García, C. Ybarra-Moncada, A.M. Castillo-González Huatusco and Plátano varieties. In the exact same order, the above varieties recorded the lowest total betalain content and are thus considered to be low-pigmented varieties. The Tzaponopal Rojo variety had the darkest color pulp and also recorded the lowest L. The pulp of this variety recorded the highest total betalain content, whereas its IC50 was the lowest. Alteña Blanca had the clearest peel color since it presented the greatest L; however, the peel of this variety also had the lowest IC50, (i.e., the highest antioxidant activity per unit weight). This could indicate that phytochemicals other than pigments were involved and contributed to the antioxidant activity. Copena CEII, Copena VI, and Tzaponopal Rojo presented the lowest peel L; these varieties consistently have dark colors (purple-red) and in this analysis showed low hue values (tone angle). Most varieties exhibited lower hue values in the pulp than in the peel (i.e., the pulp was redder than the peel). The peel and pulp showed similar hue values only in some varieties (Huatusco, Morada, and Tzaponopal Rojo). Pulp hue values followed a trend very similar to that described for peel; the lowest hue values (less than 9°) were observed in the pulp of the Copena CEII and Copena VI varieties, which consistently had the highest total betalain content. Peel hue values could be divided into four distinct groups: (a) the Alteña Blanca variety, which had a high value (greater than 100°) and consistently presented the lowest total betalain content in the peel; (b) the Plátano and Huatusco varieties, with medium values (52°- 55°) and relatively low total betalain content; (c) most other varieties, with low values (18°- 20°) and relatively high total betalain content; and (d) the Roja Villanueva, which had a very low value (less than 5°) and consistently presented the highest total betalain content. Except for the Alteña Blanca variety, chroma values (color purity) were higher in the pulp than in the peel. The chroma in descending order was as follows: Alteña Roja > Solferino > Plátano > Tzaponopal Rojo > Roja Villanueva > Morada > Copena VI > Jade > Copena CEII > Huatusco > Alteña Blanca. The greater the chroma, the more vibrant and attractive the colors. Results indicate that the pulp in varieties with higher chroma values has more attractive color than that in varieties with lower chroma values. The highest chroma values in peel were exhibited by the yellow varieties (Alteña Blanca and Plátano), meaning that these had more defined and brighter colors; however, they showed the lowest total betalain content, which indicates that different pigments are possibly responsible for their colors. The Roja Villanueva variety also ex- hibited a relatively high chroma value, which, in this case, may be associated with high total betalain content. Neither in the peel nor in the pulp was there any clear association between color purity (chroma) and pigment content or antioxidant activity. In the international trade of prickly pear, major markets demand colorful red and yellow fruits, the brighter the better. The typical colors of the fruits are due to the presence of certain pigments (betalains, anthocyanins, and carotenes), which have antioxidant capacity. Therefore, it is important to analyze color and antioxidant content to identify phytogenetic materials with high nutraceutical Tab. 4: Color parameters of the fruit of 11 varieties and species of prickly pear (Opuntia sp.) harvested at the Universidad Autónoma Chapingo Experimental Station, Chapingo, Mexico. Species Variety Tissue* (L) (Hue) (Chroma) Opuntia sp. Alteña Blanca Peel 38.23b 100.96a 17.90eg Pulp 45.83a 88.87b 12.03hj Opuntia sp. Alteña Roja Peel 23.51e 9.91hj 10.39jl Pulp 18.73gh 21.25e 27.43a O. ficus indica Huatusco Peel 25.82ed 52.57c 10.54il Pulp 36.11b 54.14c 14.74fh O. ficus indica Solferino Peel 22.83ef 18.52ef 11.49hk Pulp 18.62gi 13.12fi 27.39a O. ficus indica Roja Villanueva Peel 19.81fg 4.73 j 14.21gi Pulp 19.67fh 15.75eg 23.35bc O. ficus indica Jade Peel 19.71fh 13.52 fi 7.89 km Pulp 15.29ik 9.01hj 20.38ce O. ficus indica Copena CEII Peel 19.31gh 14.02fh 6.32m Pulp 14.68jk 8.54 hj 18.47df O. ficus indica Copena VI Peel 19.32gh 12.01gi 6.97 lm Pulp 16.31hj 7.98ij 21.70cd O. megacantha Morada Peel 19.39fh 12.21gi 8.24km Pulp 15.52ik 13.27fi 23.12bc O. megacantha Plátano Peel 29.25cd 54.91c 14.52gh Pulp 31.08c 43.08d 25.56ab O. robusta/Larreyi Tzaponopal Rojo Peel 19.31gh 12.31gi 6.95 lm Pulp 12.60k 11.75gi 25.56ab CV 5.79 8.09 9.02 *Fresh weight; Lightness (L); Tone (Hue); Purity (Chroma); CV = Coefficient of variation. Means with the same letters in a column are not significantly different (Tukey, P ≤ 0.05). Nutraceutical components of prickly pear (Opuntia sp.) 217 potential. According to the results of the present study, peels of the Roja Villanueva, Copena CEII, Copena VI, and Tzaponopal Rojo varieties could be outstanding raw material for the food industry because of their high betacyanin content. Principal component analysis was used to group the varieties by type of antioxidant components (JOLLIFFE, 2005). The principal com- ponents (PC 1 and PC 2) explained 69.6% of data variability (40.9% and 28.8%, respectively) (Fig. 2). Fig. 2 depicts the makeup of the pulp of four groups of prickly pear fruit varieties: Group I (Copena VI and Tzaponopal Rojo varieties) had a high betalain content and the highest IC50; Group II (Jade, Morada, Copena CEII, Plátano, and Huatusco varieties) presented an intermediate total phenol content and LC50; Group III (Roja Villanueva variety) had the lowest IC50; and Group IV (Alteña Blanca, Alteña Roja, and Solferino varieties) had the highest phenol and vitamin C concentrations, respectively. Finally, it is recommended that research on the nutraceutical quality of other genotypes be intensified, aiming to increase their demand, generate new spaces for commercialization, and contribute to conservation of the country’s cultural identity. and flavonoid content, as well as the highest antioxidant activity (IC50); however, no ascorbic acid was detected in it. 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