Luciana de Siqueira Oliveira

Anti-oxidative and proteolytic activities and protein profile of laticifer cells of Cryptostegia grandiflora, Plumeria rubra and Euphorbia tirucalli

In this study, proteins extracted from laticifer cells of three plants were examined by electrophoresis, mass spectrometry (MALDI-TOF) and characterized in respect of proteolytic, chitinolytic and anti-oxidative activities by means of zymography and colorimetric assays. Acidic proteins with molecular masses between 12.5 and 74.5 kDa predominated in laticifers of P. rubra. This profile was not found in laticifers of C. grandiflora and E. tirucalli. The later was poor in respect of proteins. Strong anti-oxidative activity of superoxide dismutase (E.C. 1.15.1.1) was detected in P. rubra and C. grandiflora latices, and to a lesser extent ascorbate peroxidase (E.C. 1.11.1.1) and isoforms of peroxidase were seen. Catalase (E.C. 1.11.1.6) was detected only in laticifer cells of C. grandiflora. Chitinase (E.C. 3.2.1.14) was the sole activity found in laticifer cells of E. tirucalli, but was also detected in the other latices. The strong proteolytic activity of C. grandiflora was shown to be shared by at least three distinct cysteine proteinases (E.C. 3.4.22.16). Serine, aspartic and metaloproteinases were not detected. In laticifer cells of P. rubra, four proteinases were detected, including cysteine and serine types. This study reports new protein data of laticifers from plants that have been poorly investigated in this respect and contributes to the understanding of biochemical and functional aspects of laticifers in plants.

Antioxidant metabolism during fruit development of different acerola (Malpighia emarginata D.C) clones.

The present research work describes the major changes in the antioxidant properties during development of acerola from five different clones. Ripening improved fruit physicochemical quality parameters; however, total vitamin C and total soluble phenols (TSP) contents declined during development, which resulted in a lower total antioxidant activity (TAA). Despite the decline in TSP, at ripening, the anthocyanin and yellow flavonoid content increased and was mainly constituted of cyanidin 3-rhamnoside and quercetin 3-rhamnoside, respectively. The activities of oxygen-scavenging enzymes also decreased with ripening; furthermore, the reduction in vitamin C was inversely correlated to membrane lipid peroxidation, indicating that acerola ripening is characterized by a progressive oxidative stress. Among the studied clones, II47/1, BRS 237, and BRS 236 presented outstanding results for vitamin C, phenols, and antioxidant enzyme activity. If antioxidants were to be used in the food supplement industry, immature green would be the most suitable harvest stage; for the consumers market, fruit should be eaten ripe.

The influence of processing and long-term storage on the antioxidant metabolism of acerola (Malpighia emarginata) purée

Este trabalho avaliou o efeito do processamento e do tempo de armazenamento sobre o potencial antioxidante e atividade de enzimas antioxidantes de polpa congelada de frutos de seis clones de aceroleira. Foram colhidas acerolas maduras dos clones BRS 235, BRS 236, BRS 237, BRS 238, II47/1 e BRS 152; a polpa foi processada, acondicionada em sacos plasticos de polietileno selados a vacuo e armazenada em freezer domestico a -18 °C por 11 meses. Amostras de cada clone foram analisadas no dia colheita/processamento e a cada 30 dias quanto aos compostos bioativos antioxidantes, a atividade de enzimas antioxidantes e a atividade antioxidante total. As polpas de acerola apresentaram uma diminuicao dos antioxidantes nao enzimaticos e um aumento da atividade das enzimas antioxidantes, indicativo de um mecanismo compensatorio entre antioxidantes enzimatico e nao enzimatico. Na polpa de acerola, antocianinas e polifenois estao fortemente correlacionados com o conteudo de solidos soluveis e de vitamina C, destacando os polifenois como o principal contribuinte para a atividade antioxidante total. A polpa do clone II47/1 teve um excelente desempenho em relacao ao potencial antioxidante e o melhor periodo de armazenamento a -18 °C seria de 150 dias, para todos os clones estudados.

THERMOSTABILITY OF ANTIOXIDANT AND DETERIORATIVE ENZYMES FROM SOURSOP AND CASHEW APPLE JUICES

This work aimed to evaluate the thermostability of antioxidant (superoxide dismutase - SOD, catalase - CAT and ascorbate peroxidase - APX) and deteriorative (guaiacol peroxidase - G-POD, polyphenoloxidase - PPO, pectin-methylesterase - PME and polygalacturonase - PG) enzymes from soursop and cashew apple juices. Juices were prepared homogenizing ripe fruit pulps and submitting to different thermal treatments (55, 65, 75, 85 and 95°C) for different time period (1, 3, 5, 10, 15, 20 and 30 min) then enzymatic activities were evaluated. The treatments at 55°C for soursop juice and at 75°C for cashew apple juice presented the best results, considering the low residual activities for deteriorative enzymes and the retained activity of SOD. Our results suggest appropriate technological condition to thermal processing from soursop and cashew apple juice whereby ensuring quality beyond their functionality.