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Estudo comparativo do perfil químico e das bioatividades de três macroalgas marinhas em diferentes contextos ecológicos
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Abstract(s)
Esta dissertação teve como principal objetivo comparar três espécies de macroalgas – Gracilaria gracilis, Sargassum muticum e Ulva sp. – colhidas em épocas distintas do ano e em locais distintos da costa portuguesa, através da caraterização do perfil bioquímico e das bioatividades (antimicrobianas, antioxidantes e bioestimulantes).
A caraterização ecológica dos locais demonstrou condições ambientais contrastantes: a Figueira da Foz apresenta forte influência marítima e alguma fluvial, com águas relativamente frias; a Lagoa de Óbidos é marcada por águas calmas e elevada variabilidade físico-química; e Peniche carateriza-se pelas praias rochosas, sujeitas a forte agitação marítima. Estas diferenças refletem-se sobretudo na salinidade e no oxigénio dissolvido, condicionando a fisiologia e a composição bioquímica das algas. Em diferentes análises observaram-se diferenças significativas entre espécies e também entre locais, enquanto a sazonalidade mostrou menor impacto nos resultados.
Os resultados mostraram que o teor de humidade é superior nas amostras colhidas em setembro/novembro, indicando um efeito sazonal. No teor de cinzas, G. gracilis possui os teores mais baixos, sem diferenças significativas entre épocas e locais. Quanto ao conteúdo mineral, destaca-se o cálcio, variando entre 1,91 e 17,91 mg/g, enquanto o arsénio excede os limites regulamentados, em todas as amostras. Além disso, a G. gracilis apresentou o maior teor de hidratos de carbono, enquanto o teor proteico variou entre espécies, com a Ulva sp. de Buarcos de março (UBM) a obter o valor máximo (4,78%).
Relativamente à matéria gorda total, a Ulva sp., registou o valor mais baixo (0,52%), enquanto o S. muticum apresentou o valor máximo (3,23%), exibindo predominantemente ácido palmítico (C16:0) e ácido oleico (C18:1 n9 cis). O rácio ómega-6/ómega-3, por sua vez, é superior a 1 nas amostras de S. muticum (entre 1,9 e 2,73) e maioritariamente inferior a 1 na Ulva sp., exceto na UBM.
Na análise dos pigmentos fotossintéticos, a clorofila a é o pigmento mais abundante, atingindo 8,45 mg/g em S. muticum. Adicionalmente, a fucoxantina variou entre 0,77 e 1,87 mg/g em S. muticum e a ficoeritrina-R oscilou entre 0,047 e 0,549 mg/g em G. gracilis. Também se verificou que a abundância de pigmentos é fortemente influenciada pelo local de recolha.
Os extratos hidroetanólicos não exibiram atividade antimicrobiana relevante, mas demonstraram forte atividade antioxidante, destacando-se a UBM (93,85% de inibição no DPPH e 564,16 μmol Fe/g no FRAP). No QTP, por sua vez, destacou-se o S. muticum de Óbidos em março, com uma concentração de 38,42 mg GAE/g.
As frações residuais dos extratos revelaram um elevado potencial bioestimulante nas sementes de alface e tomate, sendo que, relativamente ao crescimento, destaca-se a Ulva sp..
Estas descobertas evidenciam que a composição bioquímica e as bioatividades das espécies em estudo são influenciadas pela espécie, pelo local e pela sazonalidade, realçando o seu potencial como recursos de valor acrescentado na área nutricional, agronómico e biotecnológico.
The main objective of this dissertation was to compare three species of macroalgae – Gracilaria gracilis, Sargassum muticum and Ulva sp. – harvested at different times of the year and at different locations along the Portuguese coast, by characterising their biochemical profile and bioactivities (antimicrobial, antioxidant and biostimulant). The ecological characterisation of the locations revealed contrasting environmental conditions: Figueira da Foz has a strong maritime influence and some fluvial influence, with relatively cold waters; Lagoa de Óbidos is marked by calm waters and high physical-chemical variability; and Peniche is characterised by rocky beaches, subject to strong sea turbulence. These differences are mainly reflected in salinity and dissolved oxygen, conditioning the physiology and biochemical composition of the algae. In different analyses, significant differences were observed between species and between locations, while seasonality had less impact on the results. The results showed that the moisture content is higher in samples collected in September/November, indicating a seasonal effect. In terms of ash content, G. gracilis has the lowest levels, with no significant differences between seasons and locations. As for mineral content, calcium stands out, varying between 1.91 and 17.91 mg/g, while arsenic exceeds the regulated limits in all samples. In addition, G. gracilis had the highest carbohydrate content, while the protein content varied between species, with Ulva sp. from Buarcos of March (UBM) obtaining the maximum value (4.78%). In terms of total fat content, Ulva sp. recorded the lowest value (0.52%), while S. muticum recorded the highest value (3.23%), predominantly exhibiting palmitic acid (C16:0) and oleic acid (C18:1 n9 cis). The omega-6/omega-3 ratio, in turn, is greater than 1 in S. muticum samples (between 1.9 and 2.73) and mostly less than 1 in Ulva sp., except in UBM. In the analysis of photosynthetic pigments, chlorophyll a is the most abundant pigment, reaching 8.45 mg/g in S. muticum. Additionally, fucoxanthin ranged from 0.77 to 1.87 mg/g in S. muticum, and phycoerythrin-R ranged from 0.047 to 0.549 mg/g in G. gracilis. It was also found that pigment abundance is strongly influenced by the collection site. The hydroethanolic extracts did not exhibit significant antimicrobial activity, but demonstrated strong antioxidant activity, with UBM standing out (93.85% inhibition in DPPH and 564.16 μmol Fe/g in FRAP). In QTP, on the other hand, S. muticum from Óbidos of March stood out, with a concentration of 38.42 mg GAE/g. The residual fractions of the extracts revealed a high biostimulant potential in lettuce and tomato seeds, with Ulva sp. standing out in terms of growth. These findings show that the biochemical composition and bioactivities of the species under study are influenced by species, location and seasonality, highlighting their potential as value-added resources in the nutritional, agronomic and biotechnological fields.
The main objective of this dissertation was to compare three species of macroalgae – Gracilaria gracilis, Sargassum muticum and Ulva sp. – harvested at different times of the year and at different locations along the Portuguese coast, by characterising their biochemical profile and bioactivities (antimicrobial, antioxidant and biostimulant). The ecological characterisation of the locations revealed contrasting environmental conditions: Figueira da Foz has a strong maritime influence and some fluvial influence, with relatively cold waters; Lagoa de Óbidos is marked by calm waters and high physical-chemical variability; and Peniche is characterised by rocky beaches, subject to strong sea turbulence. These differences are mainly reflected in salinity and dissolved oxygen, conditioning the physiology and biochemical composition of the algae. In different analyses, significant differences were observed between species and between locations, while seasonality had less impact on the results. The results showed that the moisture content is higher in samples collected in September/November, indicating a seasonal effect. In terms of ash content, G. gracilis has the lowest levels, with no significant differences between seasons and locations. As for mineral content, calcium stands out, varying between 1.91 and 17.91 mg/g, while arsenic exceeds the regulated limits in all samples. In addition, G. gracilis had the highest carbohydrate content, while the protein content varied between species, with Ulva sp. from Buarcos of March (UBM) obtaining the maximum value (4.78%). In terms of total fat content, Ulva sp. recorded the lowest value (0.52%), while S. muticum recorded the highest value (3.23%), predominantly exhibiting palmitic acid (C16:0) and oleic acid (C18:1 n9 cis). The omega-6/omega-3 ratio, in turn, is greater than 1 in S. muticum samples (between 1.9 and 2.73) and mostly less than 1 in Ulva sp., except in UBM. In the analysis of photosynthetic pigments, chlorophyll a is the most abundant pigment, reaching 8.45 mg/g in S. muticum. Additionally, fucoxanthin ranged from 0.77 to 1.87 mg/g in S. muticum, and phycoerythrin-R ranged from 0.047 to 0.549 mg/g in G. gracilis. It was also found that pigment abundance is strongly influenced by the collection site. The hydroethanolic extracts did not exhibit significant antimicrobial activity, but demonstrated strong antioxidant activity, with UBM standing out (93.85% inhibition in DPPH and 564.16 μmol Fe/g in FRAP). In QTP, on the other hand, S. muticum from Óbidos of March stood out, with a concentration of 38.42 mg GAE/g. The residual fractions of the extracts revealed a high biostimulant potential in lettuce and tomato seeds, with Ulva sp. standing out in terms of growth. These findings show that the biochemical composition and bioactivities of the species under study are influenced by species, location and seasonality, highlighting their potential as value-added resources in the nutritional, agronomic and biotechnological fields.
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Gracilaria gracilis Sargassum muticum Ulva sp. Local Sazonalidade Bioatividades
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