Browsing by Author "Coelho, Natacha"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
- Bioactive profile, bioaccessibility and antioxidant activity of diatoms: a comparative studyPublication . Rocha, Helena R.; Coelho, Marta; Coelho, Natacha; Morais, Rui M. S. C.; Pintado, Manuela E.; Gomes, Ana M.Diatoms are microalgae with significant biotechnological potential due to their richness in bioactive compounds, including carotenoids and phenolics, contributing to their antioxidant properties. This study aims to compare the bioactive profile and antioxidant activity of three diatom species: Chaetoceros calcitrans, Nannofrustulum shiloi, and Cylindrotheca fusiformis cultivated in closed Flat Panel photobioreactors by Necton S.A. The biomass was harvested via centrifugation, freeze-dried, milled, and vacuum-packed for subsequent analysis.Carotenoids were extracted using ethanolic extraction assisted by ultrasound and analyzed through HPLC-DAD. The Total phenolic content (TPC) was determined using the Folin-Ciocalteu method, considering both free and bound phenolics to provide a comprehensive understanding of their distribution. Antioxidant activity was evaluated using ABTS, ORAC, and DPPH assays, offering complementary insights into the radical-scavenging potential of the diatom species. Additionally, a bioaccessibility assessment was performed using the standardized INFOGEST in vitro model to evaluate the stability of these bioactive compounds.Carotenoid analysis revealed distinct profiles among the species. N. shiloi exhibited the highest levels of β-carotene and zeaxanthin, highlighting its strong potential as a source of antioxidant pigments, whereas C. fusiformis showed a balanced composition of β-carotene, zeaxanthin, and other carotenoids, suggesting a varied antioxidant capacity. In contrast, C. calcitrans contained comparatively lower levels of these carotenoids. In addition to carotenoids, phenolic compounds play a significant role in the antioxidant potential of these diatoms. The TPC varied significantly, with C. fusiformis presenting the highest levels, followed by N. shiloi and C. calcitrans. Besides the differences in the results of the antioxidant activity among species, all exhibited considerable antioxidant capacity, suggesting the presence of multiple bioactive compounds contributing to distinct yet effective mechanisms of action.These findings highlight the potential of diatoms as sources of natural bioactives, particularly for nutraceutical and pharmaceutical applications. The study underscores the importance of species selection in maximizing bioactive compound yield and antioxidant properties, paving the way for further exploration in functional food and cosmetic industries.
- Carotenoid-microbiota dynamics: in vitro analysis of gut modulation and associated health benefitsPublication . Rocha, Helena R.; Coelho, Marta; Coelho, Natacha; Morais, Rui M.S.C.; Pintado, Manuela E.; Gomes, Ana M.Carotenoids are bioactive compounds with recognized health benefits, yet their full potential is limited by poor bioaccessibility and complex interactions within the gastrointestinal tract. This study aimed to investigate the digestion, absorption, and gut microbiota modulation of three carotenoids (β-carotene, lutein, lycopene), a mixed carotenoid solution, and the red alga Osmundea pinnatifida. Using a simulated gastrointestinal digestion model (INFOGEST), combined with dialysis and in vitro fecal fermentation, we evaluated carotenoid recovery, antioxidant capacity, antidiabetic and antimutagenic activities, and short-chain fatty acid (SCFA) production. Results demonstrated low carotenoid recovery and structural transformation during digestion, with the mixed carotenoid solution exhibiting the highest antioxidant activity. Lutein and the mixed group also showed significant α-glucosidase inhibition, suggesting antidiabetic potential. Fermented samples increased the production of SCFAs and significantly modulated the gut microbiota, enhancing beneficial taxa such as Lachnospiraceae. These findings highlight the potential of carotenoids and O. pinnatifida in supporting gut health and preventing noncommunicable diseases through microbiota-mediated mechanisms.
- Linking bioaccessibility and carotenoids to antioxidant activity in diatomsPublication . Rocha, Helena R.; Coelho, Marta; Coelho, Natacha; Morais, Rui M. S. C.; Pintado, Manuela; Gomes, Ana M.Diatoms are photosynthetic microalgae with a siliceous cell wall and remarkable adaptability, making them a sustainable and renewable resource for high-value bioactive compounds (1,2). Their rapid growth, efficient carbon fixation, and minimal land and freshwater requirements (1,2) position them as attractive candidates for the development of eco-friendly products in the nutraceutical, pharmaceutical, and cosmetic industries. Among their most relevant metabolites are carotenoids and phenolic compounds, which exhibit strong antioxidant properties (3,4,5). This study explores the carotenoid profile of Chaetoceros calcitrans, Nannofrustulum shiloi, and Cylindrotheca fusiformis, and evaluates their antioxidant capacity using ABTS and DPPH assays. Furthermore, the natural bioaccessibility of carotenoids was assessed using the INFOGEST in vitro digestion model, highlighting the relevance of these compounds under physiological conditions and their potential for sustainable functional applications.
- Nutritional profiling and stability analysis of selected microalgaePublication . Rocha, Helena R.; Coelho, Marta; Coelho, Natacha; Morais, Rui; Pintado, Manuela E.; Gomes, Ana M.Microalgae are emerging as a valuable source of nutrients and bioactive compounds1, offering substantial potential for applications in food2. This study provides a comprehensive biochemical characterisation of several microalgae species, including Chaetoceros calcitrans, Cylindrotheca fusiformis, and Nannofrustulum shiloi, focusing on protein content, mineral composition, amino acid profile, and shelf-life stability. In terms of protein content, Chaetoceros calcitrans exhibited the highest concentration at approximately 42% (w/w), followed by Cylindrotheca fusiformis and Nannofrustulum shiloi, which had protein contents of around 31% (w/w) and 27% (w/w), respectively. These findings highlight relevant protein levels and significant variations among different microalgae species, necessitating future studies on their quality and bioavailability. Mineral analysis revealed that Nannofrustulum shiloi contains about 70% calcium. Additionally, this microalgae is rich in sodium (Na), potassium (K), magnesium (Mg), and iron (Fe). Importantly, no heavy metals were detected in any of the analysed species, confirming their safety for food applications. Amino acid profiling of lyophilised biomass from Chaetoceros calcitrans and Cylindrotheca fusiformis showed high concentrations of essential amino acids, including leucine, isoleucine, methionine, phenylalanine, and threonine (ranging from 1.10 to 8.42 g/100 gDW). Shelf-life assessments revealed that Nannofrustulum shiloi maintained a stable amino acid composition over time, with only minor variations between the initial (T0) and subsequent (T2) storage periods (October 2023 and April 2024, respectively), suggesting that the dried biomass of this species retains its nutritional properties during extended storage. Conversely, Cylindrotheca fusiformis displayed notable changes in amino acid levels after storage, indicating that storage conditions can significantly affect its protein composition. These results underscore the nutritional potential and stability of certain microalgae species, particularly Nannofrustulum shiloi, for food applications. The observed variations in protein and amino acid profiles across species provide valuable insights for the development of functional food ingredients derived from microalgae.