Orientador: Prof. Dr. Jesuí Vergílio Visentainer

Data da Defesa: 22/04/2013



 INTRODUCTION. Brazil boats a large number of native and exotic fruits and the interest in exploiting new species during recent years has arisen because many of them are rich in antioxidants and are thus able to protect the human metabolism against oxidative stress. In addition to the significant impact on human health, antioxidants may also have application in the food industry and pharmaceutical industry. Recent research studies of bioactive compounds in peels and seeds of fruits, considered subproducts, found significant levels of these compounds, which strengthens the possibilities of using these parts of the fruit as a source of nutraceutical compounds and application in the food industry to increase stability and shelf life of food products. Jambolan (Syzygium cumini), Maria Preta (Solanum nigrum), Inga (Inga edulis) and Japanese grape (Hovenia dulcis) are fruits cultivated in Brazil, but few studies have been published concerning their bioactive compounds and antioxidant activity of parts of these fruits individually. Therefore, need to be properly investigated, in order to evaluate its potential as a source of antioxidants.
AIMS. The aims of this study were to evaluate the antioxidant activity in different parts of Jambolan, Maria Preta, Inga and Japanese grape via the activity of free- radical scanveging of 1,1-diphenyl-2 picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assay and quantify the total phenolic compounds, total flavonoids, total anthocyanins and identify fatty acids and phenolic compounds by chromatographic methods.
MATERIAL AND METHODS. Jambolan, Maria Preta, Inga and Japanese grape were obtained from farmers in the region of the state of Paraná. Parts of the fruit were separated, crushed, transferred to plastic bags, subjected to vacuum and stored in a freezer at –18 °C. The methanol extracts were prepared using 10 g of each part of fruit and 100 mL of methanol. Was stirred for 4 h, the extracts were filtered and concentrated on a rotary evaporator. The dried extracts were stored at –18 °C until analyzed. Analyses of DPPH, FRAP, total phenolics, flavonoids and identification of bioactive compounds by high performance liquid chromatography (HPLC) were performed with methanol extracts. The antioxidant activity of methanolic extracts was evaluated via the activity of free-radical scavenging of 1,1-diphenyl-2-picrylhydrazyl (DPPH), based on the method of El-Massry, El-Ghorab, and Farouk (2002). The results are expressed as Trolox equivalents (μMTE 100 g−1) and also estimated by the FRAP assay, according to Benzie and Strain (1996). The results are expressed as equivalents in μM FeSO4 100 g−1. The content of total phenolic compounds (TPC) was determined according to Shahidi and Naczk method (1995) and the results were expressed as gallic acid equivalents (GAE 100 mg g−1). The total flavonoid (TF) was determined according Buriol et al. (2009) and the results were expressed as mg of quercetin equivalents (QE 100 mg g−1). Extraction of total anthocyanins (TA) was performed according to Lee and Francis (1972) and the results were expressed in mg 100 g−1 sample. The moisture, ash and crude protein (CP) were determined according to AOAC (Cunniff, 1998). The total lipids (TL) were extracted by the method of Bligh and Dyer (1959). The fatty acid methyl esters were prepared by methylation of total lipids according to Hartman and Lago (1973) and separated by chromatography according to Martin et al. (2008). The identification of fatty acids (FA) were performed by comparison of retention times with a mixture of methyl esters (189-19). The quantification of FAs was performed as described by Joseph and Ackman (1992), using methyl tricosanoato as the internal standard (23:0). Was used a correction factor and a conversion factor to express the results in FAs instead of methyl esters according Visentainer (2012). The results were converted from mg g−1 for g 100 g−1 of FAs. The identification of phenolic compounds was performed by HPLC according Fratianni et al. (2007) and the results were expressed as mg 100 g−1. Statistical analysis of the results were presented as mean ± standard deviation. Data were analyzed by analysis of variance (ANOVA). The Tukey test (p = 0.05), was used to evaluate the significant differences between the means of the samples. Pearson’s correlation coefficient (r) was calculated for each part of fruit to relate the contents of TPC, TF and TA with DPPH and FRAP.
RESULTS. The moisture content of fruits ranged from 4.85% in seeds to 86.35% in pulps of Maria Preta. The highest levels of ash (2:46%), PB (17:08%) and TL (8.73%) were found in Japanese grape seeds. The Jambolan peels excelled in TA content (63.31 mg 100 g−1). The highest concentration of TPC (518.18 mg GAE 100 g−1) and TF (76.54 mg QE 100 g−1) were found in the peel and pulp of Japanese grape. The same parts of the Japanese grape also had the highest antioxidant activity by DPPH (13240.6 μMTE 100 g−1) and FRAP (690.68 μMFeSO4 100 g−1). Pearson’s correlation coefficient (r) showed moderate positive results in pulps and peels between of TPC and DPPH analysis, in pulps between TF and DPPH analysis and in pulps between TA and DPPH analysis. In seeds, between TPC and DPPH analysis, in peels and seeds between TF and DPPH, in pulps, peels and seeds between TPC, TF and FRAP and pulps, between TA and FRAP analysis of the results were strongly positive. The correlation was negative in peels and seeds from TA with DPPH and TA with FRAP, respectively. In peels and seeds between TA with DPPH and FRAP, the correlation was zero, respectively. Only the Jambolan seeds showed ellagic acid (36.30 mg 100 g−1) and epicatechin (48.14 mg 100 g−1) and present high levels of content of gallic acid (571.05 mg 100 g−1). Maria Preta peels showed higher concentrations of kaempferol (573.80 mg 100 g−1). The FA oleic (18:1 n–9) was found in greater proportion in pulp (18.19 mg 100 g−1), peel (257.24 mg 100 g−1) and seed (291.01 mg 100 g−1) of Jambolan, Inga pulp (97.36 mg 100 g−1) and Maria Preta seed (1891.36 mg 100 g−1). Linoleic acid (18:2 n–6) stood in Maria Preta pulp (48.09 mg 100 g−1) and peel and pulp of Japanese grape (98.69 mg 100 g−1). The arachidic acid (20:0) was the major FA in Maria Preta peel (888.22 mg 100 g−1). Inga seeds (313.70 mg 100 g−1) stood palmitic acid (16:0) and the Japanese grape seed (3985.95 mg 100 g−1), alpha-linolenic acid (18:3 n–3). Relations between FAs linoleic and linolenic (n–6/n–3) was greater than 5:1 in pulp and peel of Jambolan (51.01 and 19.54, respectively), in pulp and seed Maria Preta (51.15 and 78.30,  respectively) and Inga pulp (38.40). However, relations between the FAs were more adequate in pulp and peel of Japanese grape (2.38), Maria Preta peel (0.24), Jambolan seeds (0.06), Inga seeds (0.16) and Japanese grape seeds (0.48).
CONCLUSIONS. Jambolan peels showed significant concentration of anthocyanins. Phenolic compounds responsible for the antioxidant activity of the extracts showed the highest concentration in Jambolan seeds, followed by Japanese grape, Maria Preta and Inga. The concentration of bioactive compounds identified by HPLC in peel followed the decreasing scale: Maria Preta > Jambolan > Japanese grape and pulps: Japanese grape > Jambolan> Maria Preta > Inga. DPPH and FRAP methods were able to represent the antioxidant activity of the samples with relation to concentration of bioactive compounds only in fruit pulp. Japanese grape seed has excelled content of alpha-linolenic acid, a FA essential for human health. These results demonstrate that these seeds have significant levels of nutrients, in addition, high levels of bioactive compounds found in peels and pulps of Japanese grape, Maria Preta peels and Jambolan seeds confirm the antioxidant potential of these parts of fruit and may be considered as a source of natural antioxidants.
KEYWORDS: Brazilian fruits, bioactive compounds, antioxidant activity, fatty acids

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