Antioxidant activity of black bean (Phaseolus vulgaris L.) protein hydrolysates

Abstract The objective of this work was to study the effect of enzymatic hydrolysis of black bean protein concentrate using different enzymes. Bean proteins were extracted and hydrolyzed over a period of 120 min using the enzymes pepsin or alcalase. The protein hydrolysates’ molecular weight was assayed by electrophoresis and the antioxidant activity was evaluated by the capturing methods of free radicals ABTS●+ and DPPH. Electrophoretic results showed that the bands above 50 kDa disappeared, when the beans protein was subjected to hydrolysis with pepsin. The bean protein hydrolysate obtained by hydrolysis with alcalase enzyme, showed higher antioxidant activity for inhibition of the radical ABTS●+. However, the hydrolysates obtained by hydrolysis with pepsin had higher antioxidant activity for inhibition of the radical DPPH. The use of pepsin and alcalase enzymes, under the same reaction time, produced black bean protein hydrolysates with different molecular weight profiles and superior antioxidant activity than the native bean protein.

Anti-quorum sensing activity of phenolic extract from Eugenia brasiliensis (Brazilian cherry)

Abstract The aim of this study was to assess the anti-quorum sensing activity of phenolic extracts from grumixama (Eugenia brasiliensis), also known as Brazilian cherry, in concentrations that did not interfere with bacterial growth. The pulp phenolic compounds were extracted by using solid phage extraction in a mini-collumn C18 and quantified by spectrophotometry. The anti-quorum sensing activity was evaluated by testing the inhibition of violacein production in Chromobacterium violaceum and by evaluating the swarming motility in Aeromonas hydrophila and Serratia marcescens, both phenotypes regulated by quorum sensing. The phenolic extract strongly inhibited the production of violacein in C. violaceum, reducing its production in comparison with a control with no extract. No inhibition of growth was observed at the concentrations tested for quorum sensing inhibition. Confirming the quorum sensing inhibition phenotype, the extract was also able to inhibit swarming motility in S. marcescens and in A. hydrophila, although in the later the effect was marginal. Overall, these results indicate that phenolic extract from E. brasiliensis presents quorum sensing inhibitory activity most likely due to the presence of fruit phenolics which have been implicated as quorum sensing inhibitors in Gram negative bacteria.

Influence of the degree of hydrolysis and type of enzyme on antioxidant activity of okara protein hydrolysates

Abstract The objective of this work was to evaluate the antioxidant activity of protein hydrolysates obtained by the enzymatic hydrolysis of okara using an endopeptidase (Alcalase) and exopeptidase (Flavourzyme). The reaction was monitored by the pH-stat procedure in which five aliquots were collected during the hydrolysis by each enzyme, corresponding to different degrees of hydrolysis (DH). The antioxidant activities of the aliquots were evaluated by the ABTS, DPPH and FRAP methods. For the hydrolysates obtained using Alcalase, the antioxidant activities increased from: 68.6 to 99.5% (ABTS), 14.5 to 17.7% (DPPH) and 222.6 to 684.9 µM Trolox (FRAP), when the DH varied from 0 to 33.6%. With respect to Flavourzyme, the results were: 67.2 to 88.2% (ABTS), 9.5 to 18.5% (DPPH) and 168.0 to 360.3 µM Trolox (FRAP), when the DH increased up to 5.8%. The results showed that the protein hydrolysates had antioxidant capacities, which were influenced by the degree of hydrolysis and the type of enzyme.

Action of gibberellic acid (GA3) on dormancy and activity of alpha-amylase in rice seeds

To evaluate the effectiveness of gibberellic acid (GA3) in breaking rice seed dormancy and the use of alpha-amylase enzyme activity as an indicator of the dormancy level, seed from the intensively dormant irrigated cultivar Urucuia were used. The seeds were submitted to a pre-drying process in a forced air circulation chamber under 40ºC during 7 days and submersed in 30 mL of GA3 solution under 0, 10, 30 and 60 mg/L H2O concentrations, during 2, 24 and 36 hours. After the treatments, the alpha-amylase activity was determined by using the polyacrilamide electrophoresis and spectrophotometry. At the same time, the germination test was made. The results indicated a gain in germination and in alpha-amylase activity in higher concentrations and soaking time of seeds in GA3. These observations support the conclusion that soaking seed in 60 mg GA3/L during 36 hours can be used as a quick and efficient treatment in breaking rice seed dormancy and is equivalent to the forced air circulation chamber at 40ºC during 7 days. The alpha-amylase enzyme activity proved to be as an efficient marker of the seeds dormancy level.

Physiological quality, content and activity of antioxidants in soybean seeds artificially aged

The objective of this study was to evaluate physiological quality, content, and activity of antioxidants, in soybean seeds subjected to accelerated aging during different periods. Seeds of cultivars BRS 258, BRS 262 and BRS 268, subjected to accelerated aging during 12, 24, 36 and 48 hours and non-aged seeds were used. After each aging period, the seed were evaluated by tests of: germination; first count and tetrazolium. The total of phenolic compounds, total flavonoides, total of isoflavones, and activity for eliminating ABTS●+ radicals were quantified. There were differences among cultivars according to vigor and viability only after seeds were aged. Cultivars BRS 158 and BRS 268 have shown better seed physiological quality in each aging period; however, not presenting higher amounts of isoflavones and efficiency in removing free radicals. For all cultivars, the values for total of phenolic compounds, as well as total of flavonoids have shown quadratic positive behavior; the values for isoflavones remained constant and the vigor and viability showed contrary trend to activity of antioxidant agents.