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- Antioxidant activity and phenolic composition of Cv. Cobrançosa olives affected through the maturation processPublication . Sousa, Anabela; Malheiro, Ricardo; Casal, Susana; Bento, Albino; Pereira, J.A.Maturation stage is a critical feature to obtain high quality olive products, with maximized bioactivity. In this study, phenolic composition and antioxidant activity of Cv. Cobrançosa through the maturation process were evaluated.The phenolic profile was assessed by HPLC/ DAD, and antioxidant activity was studied through its reducing power and free-radical scavenging activity. Total phenols varied from 34 to 1 g/kg, respectively, in the first and last sampling dates. Oleuropein, the main phenolic in the first stages of maturation, decreased drastically during ripening. At intermediate and high maturation stages hydroxytyrosol was the predominant phenol. Globally, the reducing capacity of Cv. Cobrançosa olive fruits decreased during the maturation process but its radical scavenging activity was only slightly altered. A principal components analysis corroborated the characteristic phenolic profile and changes experienced by the olive fruit during the maturation process. These results are important to maximize Cv. Cobrançosa olive products’ quality and biological properties.
- Hazelnut (Corylus avellana L.) kernels as a source of antioxidants and their potential in relation to other nutsPublication . Delgado, Teresa; Malheiro, Ricardo; Pereira, J.A.; Ramalhosa, ElsaThe present work evaluates the potential of hazelnut kernels as a source of antioxidants to be incorporated into new products. First, the effects of extraction conditions on the isolation of hazelnut kernels’ total phenols and antioxidants were evaluated. Six conditions, involving different solvents (water, methanol and aqueous acetone) and contact times, were studied. The highest total phenol contents were obtained with boiling water for 30 min, 44.3±7.7mgGAE/gextract, and 80% (v/v) aqueous acetone solution for 24 h, 36.2±8.8mgGAE/gextract. Increasing the contact time for the acetonic extractions did not improve the total phenols content. Regarding antioxidant activity, the highest DPPH-scavenging effect value was obtained with 80% (v/v) aqueous acetone for 24 h with an effective concentration (EC50) equal to 1.12±0.07 mg/mL. When other nuts – walnuts, almonds, pine nuts and peanuts – were extracted under this condition, only walnut extract exhibited higher phenol content (268±32mgGAE/gextract), antioxidant activity as measured by reducing power (EC50 = 0.091±0.015 mg/mL) and free radical scavenging capacity (DPPH assay) (EC50 = 0.060±0.010 mg/mL) than hazelnut extract. The present work demonstrates that some nuts might be a natural source of bioactive compounds that can be incorporated into new health-related products or be substitutes of synthetic compounds of questionable safety, promoting human health and reducing disease risks.
- Organic and mineral fertilization influence on biomass and essential oil production, composition and antioxidant activity of Lippia origanoides HBKPublication . Teles, Simone; Pereira, J.A.; Oliveira, Lenaldo Muniz de; Malheiro, Ricardo; Machado, Serly Santigo; Lucchese, Angélica M.; Silva, FrancelitIn the present work, the effect of organic and mineral fertilization were evaluated on biomass produc-tion, essential oil content, essential oil composition, and antioxidant activity in comparison with plantscultivated without fertilization.Field evaluations reported that fertilization does not affect biomass and essential oil production of L.origanoides plants. However some variations were observed in the essential oils composition. Carvacrolwas the most abundant component followed by p-cymene, -terpinene, -caryophyllene, and thymol.Changes observed in the antioxidant potential of the different essential oils may be related to essential oils(EO’s) compositions. Essential oils from organic and mineral fertilization reported, respectively, higherand lower antiradical activity, while no differences were observed in the reducing power of the differenttreatments. Nevertheless, it was possible to partially discriminate the different fertilization treatmentsapplied thanks to the EO’s chemical composition and the bioactive potential.We conclude that for biomass and essential oil production, fertilization plans are not needed in L.origanoides plants at the applied conditions, however if it is necessary to enhance the bioactivity of theessential oils from L. origanoides, organic fertilization is encouraged.
- Optimal harvesting period for cvs. Madural and Verdeal Transmontana, based on antioxidant potential and phenolic composition of olivesPublication . Sousa, Anabela; Malheiro, Ricardo; Casal, Susana; Bento, Albino; Pereira, J.A.In the present study we propose to determine an approximate optimum harvesting period for table olives and olive oil of two Portuguese olive cultivars (Madural and Verdeal Transmontana) based on phenolic modifications (HPLC/DAD) and antioxidant activity (scavenging capacity on 2,2-diphenyl-1- picrylhydrazyl and reducing power). Samples were collected from almost edibility to slightly overmature. The sum of polyphenols, as well as its most abundant components oleuropein and hydroxytyrosol, decreased during this maturation period, more intensively in Madural than Verdeal Transmontana. In their green stages an antioxidant potential loss was gradually observed in both olive cultivars, while in the latter purple-black phases a slight increase in the antioxidant activity was observed. Both phenolic profile and antioxidant activity were highly correlated with the maturation process. A principal component analysis showed the particular effect of maturation in both olive cultivars. Based on the acquired knowledge we can advance that, for these cultivars and geographical region, olives harvest for table olives, traditionally collected sooner, can be performed in the middle of September. For olive oil harvesting can occur in the first days of November, giving priority to cv. Madural rather than Verdeal Transmontana, in order to enhance the bioactivity, phenolic composition and stability of olive oils.
- Arbutus unedo L. leaves as source of phytochemicals with bioactive propertiesPublication . Malheiro, Ricardo; Sá, Olga; Pereira, Eric Carvalho; Aguiar, Cristina; Baptista, Paula; Pereira, J.A.In recent years the strawberry tree (Arbutus unedo L.) is being gradually replaced by other species with higher economic value. With the ultimate goal of selecting superior genotypes, the present work was initiated to study the antioxidant and antimicrobial activities, and total phenolic content in 19 different genotypes of A. unedo leaves from the Trás-os-Montes region of Portugal. The genotype Braganc¸ a 1 contains higher total phenolic content (215.0 mg GAE/gextract) whereas the Vila Boa 4 genotype shows lower total phenolic content (148.0 mg GAE/gextract). In both methods tested to evaluate the antioxidant activity, Vila Verde and Donai displayed the highest antioxidant capacity (EC50 values of 0.088 and 0.090 mg/mL, respectively, for DPPH; EC50 values of 0.233 and 0.245 mg/mL, respectively, for reducing power assay) while Vila Boa 2 reported the lowest antioxidant potential (EC50 values of 0.142 and 0.378 mg/mL, respectively, in DPPH and reducing power methods). Linear negative correlations were established between the total phenol contents and the EC50 values for both of the antioxidant activity methods tested. Preliminary assays for antimicrobial potential showed that extracts from A. unedo leaves display antibacterial activity, with MIC values of 1 and 5 mg/mL for some Grampositive and Gram-negative bacteria, respectively. Taken together, the results suggest that A. unedo leaves are a potential source of natural compounds with valuable bioactive properties that could be explored by the pharmaceutical, chemical and food industries.
- Influence of strawberry tree (Arbutus unedo L.) fruit ripening stage on chemical composition and antioxidant activityPublication . Oliveira, Ivo; Baptista, Paula; Malheiro, Ricardo; Casal, Susana; Bento, Albino; Pereira, J.A.Arbutus unedo is a widespread shrub with economic importance, derived from the use of its berries in the production of alcoholic beverages and in folk medicine. This work intends to evaluate for the first time the effect of fruit ripening stage on antioxidant activity, total phenolic content, fatty acid profile and tocopherol composition. Ripe fruits shown higher extraction yield (45.04±2.23%) when compared to other fruit ripening stages. By contrast, total phenol contents were higher in the unripe and intermediate stage of ripeness (108 and 111 mg GAES/g dry fruit, respectively, against 60 mg/g dry fruit when ripe). Ripe and intermediate fruits shown the lower EC50 values on the DPPH radicals (0.25±0.02 mg/mL) and reducing power assay (1.09± 0.05 mg/mL), respectively. A significant correlation was established between antioxidant activity and fruits ripening stage. Fatty acid profiles were very similar between the ripening stages, being alfa-linolenic, linoleic and oleic, the three major ones. Polyunsaturated fatty acids (PUFA) represent as much as 60% of the total fatty acids, with a highly favorable omega 3/omega 6 ratio. From the analysis of the vitamin E vitamers, the most important was γ-tocotrienol, with a clear reduction in the total free vitamin E content with ripening. These results highlight that the fruits of intermediate ripeness can be regarded important sources of biologically active compounds with a fatty acid profile rich in omega-3 PUFA, properly supplemented with high vitamin E amounts.