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Browsing by Author "Machado, Maria Helena Azevedo Moreira"

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  • Chemical and biological characterization of the macroalga Undaria pinnatifida for disease prevention
    Publication . Machado, Maria Helena Azevedo Moreira; Soares, Cristina Maria Dias; Figueiredo, Sónia Adriana Ribeiro da Cunha
    The Asian kelp, Undaria pinnatifida, is one of the invasive algae identified on the Portuguese coast. Like other brown macroalgae, it has been the research focus due to its natural biocompounds with neuroprotective and antioxidant properties. These compounds have shown potential in combating neurodegenerative diseases such as Alzheimer’s and Parkinson’s. Research continues to explore ways to utilize these substances to develop treatments that could improve therapeutic options and enhance the quality of life for patients. Therefore, the aim of this study was to test the bioactivities of twenty-two extracts of U. pinnatifida using phytochemical, chemical and biological analyses to select the best extracts with a higher antioxidant, anti-inflammatory and neuroprotective potential. To obtain the extracts, an optimization of the extraction parameters was carried out, in which environmentally friendly extraction methods, such as Subcritical-Water Extraction (SWE) and Ultrassound-Assisted Extraction (UAE), were employed using organic solvents (recovered acetone, ethanol, and water). Thus, the extraction yields were determined, with notable results for extracts 21 (SWE, 30 min, 1 g:100 mL (biomass:solvent), 120°C, 20 bar) and 22 (SWE, 30 min, 1 g:100 mL (biomass:solvent), 150°C, 30 bar), yielding 53.1% and 54.5%, respectively, and extract 15 (Water, UAE, 30 min, 1 g:100 mL (biomass:solvent)) with a yield of 40.4 ± 9.1%. The total carotenoid content (TCC) was assessed, with the highest result for extract 1 (Acetone, UAE, 10 min, 1 g:50 mL (biomass:solvent)), showing 0.51 ± 0.08 mg/mg extract. Additionally, the total phenolic content (TPC) was measured, and extract 22 stood out with a result of 0.0354 ± 0.0029 mg GAE/mg extract. The richest four extracts in TCC and TPC (1, 15, 21 and 22) were selected and their antioxidant activity was subsequently evaluated. Extract 22 exhibited the highest antioxidant capacity, with values of 73.58 ± 2.62 μg TEAC/mg extract and 26.05 ± 1.29 μg AA/mg extract for the ABTS and FRAP methods, respectively. The phlorotannin content was assessed in the four extracts, with extract 1 standing out from the others, showing a result of 1.57 ± 0.14 μg phloroglucinol equivalents/mg extract. The mineral profile of the four extracts was evaluated, considering four types of elements: macro, essential trace, non-essential and toxic trace elements. Macro elements -magnesium, phosphorus, and calcium, were found mainly in extract 22, with results of 9186 ± 270, 6034 ± 108, and 8750 ± 205 mg/g extract, respectively. Essential trace elements were predominantly found in extracts 15 and 21. Extract 15 showed the highest concentrations of the essential trace elements zinc and manganese, with values of 24.0 ± 1.4 and 9.67 ± 0.43 mg/g extract, respectively. In contrast, extract 21 had the highest levels of the essential trace elements molybdenum, chromium, and iron, with values of 1.51 ± 0.10, 7.43 ± 0.59, and 67.3 ± 5.8 mg/g extract, respectively. All these metals have beneficial effects on human health, such as maintaining the health of the immune system, promoting proper kidney function and preventing osteoporosis, among others. In the four extracts, non-essential and toxic trace elements were found in low levels, except for strontium, that presented a significantly higher concentration in comparison to the other toxic elements. However, the concentration of strontium in these extracts can still be considered too low to cause any harm on the human health. The best two extracts, 1 and 22, were selected to continue the analysis of the scavenging and neuroprotective activity. The antioxidant activity was again evaluated regarding the scavenging of the nitric oxide (•NO) and hydroxyl (•OH), biologically relevant radicals. Extract 22 showed a maximum •NO scavenging percentage of 42.53 ± 2.34 (at 0.33 mg/mL) and extract 1 exhibited a maximum •OH scavenging percentage of 50.76 ± 4.90% (at 0.5 mg/mL). Lastly, regarding enzymatic activity, extract 22 did not show inhibitory activity for acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) at a concentration of 2 mg/mL. Extract 1 exhibited inhibitory activity for AChE and BuChE, with inhibition percentages of 81.61 ± 11.65 and 47.92 ± 4.77 % (0.25 mg/mL), respectively. In conclusion, the study successfully identified extracts 1 and 22 as the most promising candidates for future studies, with remarkable antioxidant, anti-inflammatory and neuroprotective properties.
    2024-09-19Master thesis Embargoed access Show more