Composition of carotenoids and anthocyanins from acerola : stability and antioxidant activity of anthocyaninc extracts from acerola and açai in model-systems. / Composição de carotenoides e antocianinas em acerola : estabilidade e atividade antioxidante em sistemas-modelo de extratos antocianicos de acerola e de açai.

Veridiana Vera de Rosso

Natural pigments, such as anthocyanins and carotenoids, are responsible for the colors found in foods, influencing its visual aspect, which is considered the main attribute for the acceptance and preference of a food product. At the same time, these pigments show important biological functions and actions, being considered human health promoters. The association between the intake of fruits and vegetables and the decreased risk of developing several chronic-degenerated disorders is already recognized, being the pigments one of the bioactive compounds responsible for such actions. Acerola and açaí are tropical fruits that contain high levels of bioactive compounds, such as carotenoids and anthocyanins. The pigments, carotenoids and anthocyanins, of two acerola varieties (Waldy Cati 30 and Olivier) harvested from a Brazilian plantation during the 2003 and 2004 summer harvests were analyzed by high performance liquid chromatography (HPLC). Both varieties presented ?-carotene (265.5 ? 1669.4 ?g/100g), lutein (37.6 ? 100.7 ?g/100g), ?-cryptoxanthin (16.3 ? 56.5 ?g/100g) and ?-carotene (7.8 ? 59.3 ?g/100g) as the major carotenoids. In both harvests, the ?-carotene, ?-cryptoxanthin and ?-carotene levels were significantly higher in the Olivier variety, whereas the lutein content was higher in the Waldy Cati variety. The two acerola varieties showed similar anthocyanin composition, being cyanidin-3-rhamnoside the major anthocyanin, followed by pelargonidin-3-rhamnoside, cyanidin-3,5-di-rhamnoside and peonidin-3-rhamnoside. The Waldy variety of acerola showed total anthocyanin content of 6.5 and 7.6 mg/100g, whilst 7.9 and 8.4 mg/100g were found in the Olivier variety, for the harvests 2003 and 2004, respectively. No statically differences for the total anthocyanin content were found between varieties and between harvests. Two brand of frozen pulp of açai presented 282 to 303 mg/100 g of total anthocyanin, with cyanidin-3-glucoside and cyanidin-3-rutinoside being found in average proportions of 13.2% and 87.5%, respectively. Acerola is considered one of the best natural source of ascorbic acid (AA) and due to this fact, the influence of AA on the stability of the acerola anthocyanin extract was evaluated using as comparison the açai anthocyanin extract which does not have AA. The experiments demonstrated that the 276 mg/100mL AA level present in the acerola anthocyanin extract is the major responsible for the intense anthocyanin degradation, since the degradation rate (kobs) of the anthocyanins in the açai extract fortified with 276mg/100mL AA, was 22 times higher than the kobs found in the natural açai extract. Although the anthocyanic model-systems from both fruits had the same AA concentration (276 mg /100mL), the kobs value observed in the acerola system was 3 times higher than that found for the açai solutions. This difference can be attributed to the 10 times higher flavonoid content found in the anthocyanin extract from açai, since the total polyphenol levels were similar in the systems from both fruits. The viability to employ the anthocyanin extracts of acerola and açai as functional ingredient was evaluated in isotonic soft drink model-systems. In all conditions studied, the anthocyanin degradation followed a first order kinetics rate. The anthocyanin stability in the isotonic soft drink system was 1.3 e 1.7 times lower compared to the citrate-phosphate buffer for the acerola and açai extracts, respectively, at pH 2.5, in the presence of light and oxygen. In all systems, the gradual fading of the red color was observed by the incresead L* values CIE parameter and decreased C* values, probably resulted respectively from the degradation of the flavillium cation and formation of chalcones. Using the stable radicals ABTS?+ and DPPH?, the radical scavenger activities of the acerola and açai anthocyanin extracts with different purification degrees were evaluated and compared to standards of anthocyanins and anthocyanidin. The crude (EB), partially purified (EPP) and purified (EP) extracts of acerola showed higher antioxidant activity than the respective extracts from açai. Since the radical scavenger activity of both crude extracts decreased with the purification process, the presence of polyphenols, flavonoids and AA in the anthocyanic crude extracts affected the antioxidant activity. The results obtained with the standards confirmed that the antioxidant activity increases with the increased number of OH groups in the B ring of the anthocyanins and that the activity decreases with the increased numbers of glycosilated sugars. Studies concerning the reactivity of anthocyanin extracts towards singlet oxygen (O2(1?g)) were carried out using the EB, EPP and EP anthocyanin extracts from acerola and açai, dimethyl-anthracene as actinometer and methylene blue as sensitizer. The physical quenching constant (kq) was determined by the sensitized photooxidation method and by the O2(1?g) phosphorescence detection. The energy level of the excited triplet state of açai anthocyanins was determined by the time resolved photoacoustics (TRP) technique. It was observed a correlation between the increased purification degree and a decrease in the O2(1?g) quenching. Among the standards evaluated, malvidin, cyanidin-3-rutinoside and cyanidin-3-glucoside, the malvidin was the best O2(1?g) quencher, independently of the method used for kq calculation. The experiments with TRP demonstrated that the açai anthocyanin triplet state had a very short life time, indicating that the O2(1?g) quenching does not occur via formation of the anthocyanin excited triplet state.

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