Red and brown seaweeds extracts: A source of biologically active compounds

Optimized Extraction Protocols for Bioactive Antioxidants from Commercial Seaweeds in Portugal: A Comparative Study of Techniques

This study aimed to optimize the extraction conditions for a valuable source of antioxidants: seaweed. Therefore, ten seaweed samples were subjected to a solid-liquid extraction (SLE), where the extraction conditions (biomass (g): solvent (mL) ratio, temperature, and time) were optimized using response surface methodology (RSM). The seaweeds were also subjected to subcritical water extraction (SWE) (140 and 190 °C) and ultrasound-assisted extraction (UAE) (10 and 20 min). The antioxidant capacity of the extracts was determined through the ferric-reducing antioxidant power and the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid). The total phenolic content revealed the significance of temperature and biomass; solvent ratio parameters in the extraction process with higher conditions generally promoting the release of phenolic compounds. Furthermore, applying RSM allowed for the identification of optimal conditions and the establishment of predictive models that can be valuable in industrial-scale extraction processes. The antioxidant potency composite index (APCI) shows that SWE at 190 °C stands out, with E. bicyclis reaching an APCI score of 46.27%. The AGREEprep evaluation showed that UAE is the most sustainable method, achieving the highest score (0.69). The results of this study contribute to the development of efficient and standardized extraction protocols for each seaweed species, allowing for the maximum yield of antioxidants.

Antimicrobial Activities of Polysaccharide-Rich Extracts from the Irish Seaweed Alaria esculenta, Generated Using Green and Conventional Extraction Technologies, Against Foodborne Pathogens

A rise in antimicrobial resistance coupled with consumer preferences towards natural preservatives has resulted in increased research towards investigating antimicrobial compounds from natural sources such as macroalgae (seaweeds), which contain antioxidant, antimicrobial, and anticancer compounds. This study investigates the antimicrobial activity of compounds produced by the Irish seaweed Alaria esculenta against Escherichia coli and Listeria innocua, bacterial species which are relevant for food safety. Microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), ultrasound-microwave-assisted extraction (UMAE), and conventional extraction technologies (maceration) were applied to generate extracts from A. esculenta, followed by their preliminary chemical composition (total phenolic content, total protein content, total soluble sugars) and antimicrobial activity (with minimum inhibitory concentration determined by broth microdilution methods), examining also the molecular weight distribution (via high performance size exclusion chromatography) and oligosaccharide fraction composition (via high-performance liquid chromatography) of the polysaccharides, as they were the predominant compounds in these extracts, aiming to elucidate structure-function relationships. The chemical composition of the extracts demonstrated that they were high in total soluble sugars, with the highest total sugars being seen from the extract prepared with UAE, having 32.68 mg glucose equivalents/100 mg dried extract. Extracts had antimicrobial activity against E. coli and featured minimum inhibitory concentration (MIC) values of 6.25 mg/mL (in the case of the extract prepared with UAE) and 12.5 mg/mL (in the case of the extracts prepared with MAE, UMAE, and conventional maceration). No antimicrobial activity was seen by any extracts against L. innocua. An analysis of molar mass distribution of A. esculenta extracts showed high heterogeneity, with high-molecular-weight areas possibly indicating the presence of fucoidan. The FTIR spectra also indicated the presence of fucoidan as well as alginate, both of which are commonly found in brown seaweeds. These results indicate the potential of antimicrobials from seaweeds extracted using green technologies.

Alaria esculenta, Ulva lactuca, and Palmaria palmata as Potential Functional Food Ingredients for the Management of Metabolic Syndrome

Hypertension, type 2 diabetes (T2D), and obesity raise an individual's risk of suffering from diseases associated with metabolic syndrome (MS). In humans, enzymes that play a role in the prevention and development of MS include angiotensin converting enzyme (ACE-1) associated with hypertension, α-amylase associated with T2D, and lipase linked to the development of obesity. Seaweeds are a rich source of bioactives consisting of proteins/peptides, polysaccharides, and lipids. This study examined the potential of seaweed-derived bioactives from Alaria esculenta, Ulva lactuca, and Palmaria palmata as inhibitors of ACE-1, α-amylase, and lipase. In vitro enzyme inhibitory assays were used to quantify the bioactivity of the seaweed extracts and compare their half-maximal inhibitory (IC50) values to recognised positive control enzyme inhibitory drugs captopril© (an ACE-1 inhibitor), acarbose (an α-amylase inhibitor), and orlistat (a lipase inhibitor). Three seaweed extracts displayed enzyme inhibitory activities equal to, or more effective than, the reference positive control drugs. These were P. palmata peptides (ACE-1 IC50 94.29 ± 3.07 µg/mL, vs. captopril© 91.83 ± 2.68 µg/mL); A. esculenta polyphenol extract (α-amylase IC50 147.04 ± 9.72 µg/mL vs. acarbose 185.67 ± 12.48 µg/mL, and lipase IC50 106.21 ± 6.53 µg/mL vs. orlistat 139.74 ± 9.33 µg/mL); and U. lactuca polysaccharide extract (α-amylase IC50 168.06 ± 10.53 µg/mL vs. acarbose 185.67 ± 12.48 µg/mL). Proximate analysis also revealed that all three seaweeds were a good source of protein, fibre, and polyunsaturated essential fatty acids (PUFAs). These findings highlight the potential of these seaweeds in the management of diseases associated with MS and as foods.

Free and bound phenolic profiles and antioxidant ability of eleven marine macroalgae from the South China Sea

Marine macroalgae are of broad interest because of their abundant bioactive phenolic compounds. However, only a few previous studies have focused on bound phenolic compounds. In this study, there were significant differences in total phenolic content, total phlorotannin content, total flavonoid content, and antioxidant ability in free and bound forms, as well as in their bound-to-free ratios, among 11 marine macroalgal species from the South China Sea. Padina gymnospora had the highest total phenolic content of free fractions, and total phlorotannin content, total flavonoid content, and antioxidant activity of free fractions. Sargassum thunbergii had the highest total phlorotannin content of bound fractions, whereas Sargassum oligocystum had the highest total flavonoid content and total phenolic content of bound fractions. Moreover, 15 phenolic acids, 35 flavonoids, 2 stilbenes, 3 bromophenols, and 3 phlorotannins were characterized and quantified using ultra-high-performance liquid chromatography with Xevo triple quadrupole mass spectrometry, and 42 phenolic compounds were reported in the bound fractions of seaweeds for the first time. Among the species, the number and amount of free and bound phenolic compounds varied greatly and the main components were different. Padina gymnospora had the largest total phenolic number, while Turbinaria ornata showed the highest total phenolic amount. Coutaric acid and diosmetin were dominant in Sargassum polycystum, and hinokiflavone was dominant in Caulerpa lentillifera, and cyanidin was dominant in the other seaweeds. Hierarchical cluster analysis was used to divide the seaweed species into seven groups. This study revealed that Padina gymnospora, Sargassum thunbergii, Turbinaria ornata, and Sargassum oligocystum are promising functional food resources.

Infesting Seaweeds as a Novel Functional Food: Analysis of Nutrients, Antioxidants and ACE Inhibitory Effects

Globalization and climate change are both contributing to an increase in the number of potentially invasive algae in coastal areas. In terms of biodiversity and financial losses, the invasiveness of algae has become a significant issue in Orbetello Lagoon. Indeed, studies from the Tuscany Regional Agency for Environmental Protection show that the reduction in dissolved oxygen caused by algal diffusion is detrimental to fisheries and biodiversity. Considering that wakame and numerous other potentially invasive seaweeds are consumed as food in Asia, we assess the nutritional and nutraceutical qualities of two potentially invasive seaweeds: Valonia aegagrophila and Chaetomorpha linum. We found that both algae are a valuable source of proteins and essential amino acids. Even if the fat content accounts for less than 2% of the dried weight, its quality is high, due to the presence of unsaturated fatty acids. Both algae are rich in antioxidants pigments and polyphenols, which can be exploited as nutraceuticals. Most importantly, human gastrointestinal digestion increased the quantity of polyphenols and originated secondary metabolites with ACE inhibitory activity. Taken together, our data strongly promote the use of Valonia aegagrophila and Chaetomorpha linum as functional foods, with possible application in the treatment of hypertension and cardiovascular diseases.

Characterization of flavor substances in cooking and seasoned cooking brown seaweeds by GC-IMS and E-nose

The flavor of algae was one of the key factors for consumer acceptance. The objective of this study was to investigate the characteristic volatile compounds in cooking and seasoned cooking edible brown seaweeds (Undaria pinnatifida and Laminaria japonica). The gas chromatography-ion mobility spectrometry (GC-IMS) and electronic nose (E-nose) analysis showed that baking resulted in significant difference in flavor of brown seaweeds. However, the overall effect of cooking was not as significant as that of the seasoning solution treatment. Additionally, brown seaweeds treated with the seasoning solution were more acceptable. Undaria pinnatifida was found to contain 72 volatile flavor compounds, while Laminaria japonica had a total of 70. This study proved the applicability of GC-IMS combined with E-nose technology to detect the changes of volatile components of brown seaweeds after processing, providing beneficial knowledge and basic theory for the deep processing of brown seaweeds.

Dehydration, Rehydration and Thermal Treatment: Effect on Bioactive Compounds of Red Seaweeds Porphyra umbilicalis and Porphyra linearis

The nutritional and bioactive value of seaweeds is widely recognized, making them a valuable food source. To use seaweeds as food, drying and thermal treatments are required, but these treatments may have a negative impact on valuable bioactive compounds. In this study, the effects of dehydration, rehydration, and thermal treatment on the bioactive compounds (carotenoids, phycobiliproteins, total phenolic content (TPC), total flavonoids content (TFC)), antioxidant (ABTS and DPPH radical scavenging activities) and anti-Alzheimer's (Acetylcholinesterase (AchE) inhibitory activities, and color properties of Porphyra umbilicalis and Porphyra linearis seaweeds were evaluated. The results revealed significant reductions in carotenoids, TPC, TFC, and antioxidant activities after the seaweeds' processing, with differences observed between species. Thermal treatment led to the most pronounced reductions in bioactive compound contents and antioxidant activity. AchE inhibitory activity remained relatively high in all samples, with P. umbilicalis showing higher activity than P. linearis. Changes in color (ΔE) were significant after seaweeds' dehydration, rehydration and thermal treatment, especially in P. umbilicalis. Overall, optimizing processing methods is crucial for preserving the bioactive compounds and biological activities of seaweeds, thus maximizing their potential as sustainable and nutritious food sources or as nutraceutical ingredients.

Effect of Porphyra haitanensis polyphenols from different harvest periods on hypoglycaemic activity based on in vitro digestion and widely targeted metabolomic analysis

The hypoglycemic effect of Porphyra is well known. Based on in vitro digestion and metabolomics, the bioaccessibility, antidiabetic activity and phenolic conversion of P. haitanensis were investigated at different harvests. Total polyphenol content (TPC), α-glucosidase inhibition and oxygen radical absorbance capacity (ORAC) increased with harvesting and digestion stages, reaching maximum at the fourth harvest. TPC and α-glucosidase inhibition after digestion reached 130-150 mg/g and 50-90 %, ORAC was 8.7-13.5 times higher than the undigestion. However, bioaccessibility in the first and second harvests was 10-80 % higher than other harvests. The phenolic content in the fourth harvest was up-regulated to 2-30 times than the first and mostly were citrus flavonoids. Redundancy analysis indicated significant correlation between phenolic metabolites and bioactivities in different harvests of P. haitanensis during digestion, with the strongest correlation coefficients were apigenin and genistein. This study provides reference for the application of P. haitanensis in treating type 2 diabetes.

The Antioxidant Activity of Undaria pinnatifida Sporophyll Extract Obtained Using Ultrasonication: A Focus on Crude Polysaccharide Extraction Using Ethanol Precipitation

Undaria pinnatifida, a marine biological resource from which antioxidants such as polysaccharides can be obtained, is primarily distributed in the coastal areas of East Asia. Reactive oxygen species (ROS) are essential for physiological processes; however, excess ROS levels in the body result in cellular oxidative damage. Several extraction methods exist; however, factors such as long extraction times and high temperatures degrade polysaccharides. Therefore, this study aimed to increase the yield of U. pinnatifida sporophyll extract (UPE), a U. pinnatifida byproduct, using ultrasonication, an environmentally friendly extraction method, and identify UPE components with antioxidant activity. UPE_2, 4, 6, and 8 extracts were obtained at extraction times of 2, 4, 6, and 8 h, respectively. UPE_8 had the highest yield (31.91%) and polysaccharide (69.22%), polyphenol, (8.59 GAE μg/mg), and fucoxanthin contents (2.3 μg/g). UPE_8 showed the greatest protective and inhibitory effects on ROS generation in H2O2-damaged Vero cells. Ethanol precipitation of UPE_8 confirmed that UPE_8P (precipitate) had superior antioxidant activity in Vero cells compared to UPE_8S (supernatant). UPE_8P contained a large amount of polysaccharides, a major contributor to the antioxidant activity of UPE_8. This study shows that UPE_8 obtained using ultrasonication can be a functional food ingredient with excellent antioxidant activity.

Elucidation and quantification health-promoting phenolic compounds, antioxidant properties and sugar levels of ultrasound assisted extraction, aroma compositions and amino acids profiles of macroalgae, Laurencia papillosa

Currently, sustainability is one of the most critical issues confronting society today. The growing of macroalgae in ocean farms appears more sustainable than agriculture on land due to it does not require any fresh water, chemical fertiliser, or soil. Macroalgae have been shown to be a sustainable marine source of amino acids, novel bioactive phenolic and aroma compounds that can be exploitation in food, cosmetic, nutraceuticals, pharmacological applications. Despite starting the huge cultivation of macroalgae in world, bioactive compounds in the edible macroalgae have not been well characterized. Ultrasound assisted extraction (UAE) and conventional extraction (CE) techniques were compared and red macroalgae, L. papillosa extracts were characterized. The highest amount of amino acid was glutamic acid (GLU) and composed of 35% was essential amino acids. UAE at 10% amplitude for 15 min showed significantly highest (p < 0.05) phenolic (212.03±3.03 mg gallic acid equivalent/100 g) as well as antioxidant activity determined by DPPH (105.69±3.02 µmol Trolox/100 g), ABTS (238.69±2.23 µmol Trolox/100 g) radical assay and FRAP value (72.47±3.13 µmol Trolox/100 g) when in comparison with CE. Furthermore, bioactive compounds in extracts were indicated as phlorotannins, flavonoids, phenolic acids and other polyphenols using liquid chromatography coupled to diode array detection and electrospray ionisation tandem mass spectrometry (LC-DAD-ESI-MS/MS). This result confirmed higher antioxidant capacity detected with the UAE. A total of 46 volatile organic compounds were identified and quantified by GC-FID/MS with HS-SPME system. This study emerges as first report to novel extraction method used and deeply characterization of L papillosa. The results seem that significant potential application in the functional food, active packaging and nutraceuticals industry.

Effect of Deployment and Harvest Date on Growth and High-Value Compounds of Farmed Alaria esculenta

Alaria esculenta is a brown seaweed farmed in many European countries for its biomass rich in useful bio compounds. This study aimed to identify the optimal growing season to maximise biomass production and quality. The seeded longlines of the brown seaweed were deployed in the southwest of Ireland in October and November 2019 and samples of the biomass were harvested in different dates, between March and June 2020. Biomass gain and composition, phenolic and flavonoid content (TPC and TFC) and biological activities (antioxidant and anti-hypertensive activities) of seaweed extracts prepared with Alcalase were evaluated. The biomass production was significantly higher for the line deployed in October (>20 kg·m-1). In May and June, an increasing amount of epiphytes was observed on the surface of A. esculenta. The protein content of A. esculenta varied between 11.2 and 11.76% and fat content was relatively low (1.8-2.3%). Regarding the fatty acids profile, A. esculenta was rich in polyunsaturated fatty acids (PUFA), especially in eicosapentaenoic acid (EPA). The samples analysed were very rich in Na, K, Mg, Fe, Mn, Cr and Ni. The content of Cd, Pb Hg was relatively low and below the maximum levels allowed. The highest TPC and TFC were obtained in extracts prepared with A. esculenta collected in March and levels of these compounds decreased with time. In general, the highest radical scavenging activities (ABTS and DPPH), as well as chelating activities (Fe2+ and Cu2+) were observed in early spring. Extracts from A. esculenta collected in March and April presented higher ACE inhibitory activity. The extracts from seaweeds harvested in March exhibited higher biological activity. It was concluded that an earlier deployment allows for maximising growth and harvest of biomass earlier when its quality is at the highest levels. The study also confirms the high content of useful bio compounds that can be extracted from A. esculenta and used in the nutraceutical and pharmaceutical industry.

Releasing Bioactive Compounds from Brown Seaweed with Novel Cold-Adapted Alginate Lyase and Alcalase

Seaweeds are considered to be third-generation renewable biomasses, the comprehensive utilization of which has drawn increasing attention in recent years. A novel cold-active alginate lyase (VfAly7) was identified from Vibrio fortis and biochemically characterized for brown seaweed utilization. The alginate lyase gene was high-level expressed in Pichia pastoris, with an enzyme yield of 560 U/mL and a protein content of 9.8 mg/mL by high-cell density fermentation. The recombinant enzyme was most active at 30 °C and pH 7.5, respectively. VfAly7 was a bifunctional alginate lyase with both poly-guluronate and poly-mannuronate hydrolysis activities. On the basis of VfAly7, a bioconversion strategy for the utilization of brown seaweed (Undaria pinnatifida) was developed. The obtained AOSs showed stronger prebiotic activity towards tested probiotics when compared to that of commercial fructooligosaccharides (FOSs), while the obtained protein hydrolysates displayed strong xanthine oxidase inhibitory activity with IC50 of 3.3 mg/mL. This study provided a novel alginate lyase tool as well as a biotransformation route for the utilization of seaweeds.

Antioxidant Activity and Inhibition of Liver Cancer Cells' Growth of Extracts from 14 Marine Macroalgae Species of the Mediterranean Sea

Macroalgae exhibit beneficial bioactivities for human health. Thus, the aim of the present study was to examine the antioxidant and anticancer potential of 14 macroalgae species' extracts, namely, Gigartina pistillata, Gigartina teedei, Gracilaria gracilis, Gracilaria sp., Gracilaria bursa pastoris, Colpomenia sinuosa, Cystoseira amentacea, Cystoseira barbata, Cystoseira compressa, Sargassum vulgare, Padina pavonica, Codium fragile, Ulva intestinalis, and Ulva rigida, from the Aegean Sea, Greece. The antioxidant activity was assessed using DPPH, ABTS^•+, ^•OH, and O₂^•- radicals' scavenging assays, reducing power (RP), and protection from ROO^•-induced DNA plasmid damage assays. Moreover, macroalgae extracts' total polyphenol contents (TPCs) were assessed. Extracts' inhibition against liver HepG2 cancer cell growth was assessed using the XTT assay. The results showed that G. teedei extract's IC₅₀ was the lowest in DPPH (0.31 ± 0.006 mg/mL), ABTS^•+ (0.02 ± 0.001 mg/mL), ^•OH (0.10 ± 0.007 mg/mL), O₂^•- (0.05 ± 0.003 mg/mL), and DNA plasmid breakage (0.038 ± 0.002 mg/mL) and exhibited the highest RP (RP_0.5AU 0.24 ± 0.019 mg/mL) and TPC (12.53 ± 0.88 mg GAE/g dw). There was also a significant correlation between antioxidant activity and TPC. P. pavonica (IC₅₀ 0.93 ± 0.006 mg/mL) exhibited the highest inhibition against HepG2 cell growth. Conclusively, some of the tested extracts exhibited significant chemopreventive properties, and so they may be used for food products.

Malondialdehyde trapping by food phenolics

The reactions between malondialdehyde and 2,5-dimethylresorcinol, orcinol, olivetol, and alkylresocinols were studied in an attempt to investigate both if this lipid oxidation product is trapped by phenolics analogously to other reactive carbonyls and to elucidate the chemical structures of the produced adducts. After being formed, malondialdehyde is both partially fractionated to acetaldehyde and oligomerized into dimers and trimers. All these compounds react with phenolics producing three main kinds of derivatives: 5(or 7)-alkyl-7(or 5)-hydroxy-4-methyl-4H-chromene-3-carbaldehydes, 7-alkyl-9-hydroxy-6H-2,6-methanobenzo[d][1,3]dioxocine-5-carbaldehydes, and 4-(3-formylphenyl)-7-hydroxy-4H-chromene-3-carbaldehydes. A total of twenty-four adducts were isolated by semipreparative high-performance liquid chromatography (HPLC) and characterized by mono- and bi-dimensional nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). Reaction pathways to explain the formation of all these compounds are proposed. Obtained results show that phenolics can trap malondialdehyde producing stable derivatives. The function(s) that such derivatives can play in foods remain(s) to be elucidated.

A Bioactive Substance Derived from Brown Seaweeds: Phlorotannins

Phlorotannins are a type of natural active substance extracted from brown algae, which belong to a type of important plant polyphenol. Phloroglucinol is the basic unit in its structure. Phlorotannins have a wide range of biological activities, such as antioxidant, antibacterial, antiviral, anti-tumor, anti-hypertensive, hypoglycemic, whitening, anti-allergic and anti-inflammatory, etc. Phlorotannins are mainly used in the fields of medicine, food and cosmetics. This paper reviews the research progress of extraction, separation technology and biological activity of phlorotannins, which will help the scientific community investigate the greater biological significance of phlorotannins.

Antioxidant Capacities and Enzymatic Inhibitory Effects of Different Solvent Fractions and Major Flavones from Celery Seeds Produced in Different Geographic Areas in China

To extend the application of celery (Apium graveolens L.) seeds, the antioxidant and enzymatic inhibitory activities of different fractions and their main flavones were investigated. The n-butanol fractions possessed the highest total phenolic content (TPC) and total flavonoid content (TFC) values. The n-butanol fractions from Northeast China samples exhibited the strongest free radical scavenging (DPPH IC₅₀ = 20.27 μg/mL, ABTS IC₅₀ = 15.11 μg/mL) and ferric reducing antioxidant power (FRAP 547.93 mg trolox (TE)/g) capacity, while those collected from Hubei China showed the optimal cupric reducing antioxidant capacity (CUPRAC) values (465.78 mg TE/g). In addition, the dichloromethane fractions from Jiangsu samples displayed a maximum Fe²⁺ chelating capacity (20.81 mg ethylene diamine tetraacetic acid (EDTA)/g). Enzyme level experiments indicated polyphenolic compounds might be the main hypoglycemic active components. Subsequently, the enzyme inhibitory activity of nine main flavones was evaluated. Chrysoeriol-7-O-glucoside showed better α-glucosidase inhibitory activity than others. However, apigenin showed the best inhibitory effect on α-amylases, while the presence of glycosides would reduce its inhibitory effect. This study is the first scientific report on the enzymatic inhibitory activity, molecular docking, and antioxidant capacity of celery seed constituents, providing a basis for treating or preventing oxidative stress-related diseases and hyperglycemia.