ANTIOXIDANT AND BIOCHEMICAL CONTENT IN BRAZILIAN GUAVA GERMPLASM WITH WHITE, RED AND PINK PULPS

Guava is an excellent source of antioxidant compounds due to its high content of phenolics, lycopene and vitamin C. The international guava market is dominated mainly by white guava, while red guava dominates the Brazilian market. The objective of this study was to analyze the content of Brazilian guava accessions contrasting for pulp colors to support the guava breeding program, focusing on accessions with high antioxidant compound contents. Sixty guava accessions established in a germplasm bank at Embrapa Tropical Semi-Arid, Brazil were evaluated for total antioxidant activity, phenolic compounds, ascorbic acid, flavonoids, lycopene, beta-carotene, titratable acidity, soluble solids and total soluble sugars. The accessions, including white (n=10), red (n=23) and pink (n=27) pulp fruits, were grown in a randomized block design, with two replications/accession. An ANOVA was performed with the degrees of freedom based upon the three pulp color groups. White guava did not present variability for the majority of compounds, except soluble solids. Red and pink guava presented high variability (p<0.01) for most compounds, except flavonoids in pink guava and flavonoids, beta-carotene, soluble solids and total sugars in red guava. The white*red + pink pulp contrasts were significant (p<0.01) for most compounds, except for titratable acidity and soluble solids, with greater mean values in the pink + red accessions, except for total soluble sugars. The red*pink contrasts were also significant (p<0.01), except for titrable acidity and soluble solids, with greater values in the red guava accessions, except for lycopene and total soluble sugars. The compound mean values were, approximately, 1.5×, 1.4×, 1.7×, 1.8×, 2.7× and 3.1× greater for antioxidant activity, phenolic compounds, ascorbic acid, flavonoids, lycopene and beta-carotene, respectively, in the pink + red guava than white guava accessions. These results indicated that pink and red guava accessions have a greater beneficial potential and should be targeted for breeding programs. INTRODUCTION Brazil and India are the major world producers of red and white guava (Psidium guajava L.), respectively. In Brazil, guava is ranked among the top tropical fruits but fresh fruit consumption is low, around 300 g/per capita/year, whereas processed guava foods are much appreciated (Francisco et al., 2005). Cultivars with substantial concentrations of antioxidant compounds, such as vitamin C, carotenoids and phenolics (Chorilli et al., 2007), have become one of the major priorities of crop breeding programs (Carvalho et al., 2006), since such compounds are known to be active as neutralizers of free radicals and are beneficial to human health (Indap et al., 2006). Reducing free radicals can improve human health because the oxidative damage they cause to human cells is believed to trigger various chronic diseases. Free radical damage has been linked to cancer, Alzheimer’s disease, rheumatoid arthritis and cardiovascular diseases (Mahattanatawee et al., 2006). Guava is rich in antioxidant compounds and contains a high level of ascorbic acid ranging from 174.2 to 396.7 mg/100 g fresh fruit (Thaipong et al., 2006). According to Joseph et al. (2012), red-fleshed guava also contains β-carotene and lycopene carotenoids, phenolic compounds and vitamin C, all with antioxidant activities. However, guava Proc. 3 IS on Guava and Other Myrtaceae Eds.: C.A. F. Santos et al. Acta Hort. 959, ISHS 2012 126 accessions vary greatly in both quantity and type of major antioxidant compounds (Côrrea et al., 2011). According to Mahattanatawee et al. (2006), guava had the highest antioxidant potential, measured as ORAC values, total phenolics, vitamin C, and dietary fiber among ten tropical fruits, and red guava presented 1.7× and 2.0× more antioxidant activity, measured by ORAC and DPPH methods, respectively, than white guava. The objective of this study was to analyze the content of Brazilian guava accessions contrasting for pulp colors to support the guava breeding program, focusing on cultivars producing fruits with a high content of functional antioxidant compounds. MATERIAL AND METHODS Mature fruits were collected from 60 guava accessions, including white (n=10), red (n=23) pink (n=27) pulp guavas, from the Psidium active germplasm bank installed on the Experimental Field of Embrapa Semiarid, Petrolina, PE (Table 1). The accessions were separated into the three groups based on visual observation (Fig. 1). The accessions were field established in a complete randomized block design, with two replications and three plants/experimental unit, at 4.0×4.0 m plant spacing. A drip irrigation system was adopted for the field. Whole fruit without seeds from each experimental unit were used to quantify nine compounds. Fruit pulp were finely crushed in a homogenizer and stored in a freezer (-80°C) for analysis, except for titratable acidity and soluble solids, that were quantified immediately. The sixty accessions were evaluated for total antioxidant activity, phenolic compounds, ascorbic acid, flavonoids, lycopene and beta-carotene as described by Côrrea et al. (2011). The acidity was determined by the method proposed by the Adolfo Lutz Institute (2008) using 1 g fresh material in 50 ml distilled water. The extract was titrated with 0.1 N NaOH and the results expressed as percentage of citric acid. The soluble solids content was determined using digital refractometer as proposed by the Adolfo Lutz Institute (2008), and the results expressed as °Brix. The soluble solids/titratable acidity ratio was obtained by dividing soluble solids and titratable acidity values. The soluble sugars were quantified by the anthrone method (McCready et al., 1950), using 100 mg fresh material to 25 ml distilled water in a water bath maintained at 60°C for 30 min. After centrifugation at 6000 rpm for 10 min, the supernatant was removed for analysis. The results were expressed as % glucose in fresh weight (FW). An ANOVA was performed with SAS, with the degrees of freedom based upon the three pulp color groups in order to evaluate any significant contrasts among the nine evaluated compounds and the pulp color groups. RESULTS AND DISCUSSION The accessions presented high variability (p<0.01) for all compounds. White pulp guava did not present variability for the majority of the compounds, except soluble solids and lycopene, while red and pink guava presented high variability (p<0.01) for most compounds, except flavonoids in pink guava and flavonoids, beta-carotene, soluble solids and total sugars in red guava (Table 1). The white*red + pink pulp contrasts were significant (p<0.01) for most compounds, except for titratable acidity and soluble solids and the greatest mean values were found in the accessions with pink + red pulp, except for total soluble sugars. The red*pink contrast was also significant (p<0.01), except for titratable acidity and soluble solids. The greatest values were found in the accessions of red pulp fruit, except for lycopene and total soluble sugars (Table 1). Maximum values for total antioxidant activity, total phenolic compounds, free ascorbic acid, flavonoids and titratable acidity, respectively, 81.8μmoles reduced DPPH g F.W, 448 mg galic acid equivalent (GAE) 100 g FW, 409.8 mg AA 100 g FW, 46.82 rutin 100 g FW and 0.67% citric acid, were found in the red guava accessions, while pink guava accessions presented maximum values for lycopene, beta-carotene and total soluble sugars, respectively, 4.03 mg 100 g FW, 2.54 mg 100 g F.W and 13.1%. White guava presented accessions with maximum value only for soluble solids, 15.9°Brix