Comparative Study on the Effect of Phenolics and Their Antioxidant Potential of Freeze-Dried Australian Beach-Cast Seaweed Species upon Different Extraction Methodologies

Multi-Element Fingerprinting Combined with Chemometrics for Identification of Seaweeds and Innovative Risk-Benefit Assessment

Seaweeds are one of the major marine foods with high values. The diversity of seaweed species significantly impacts their quality and is closely linked to their purity and safety. For the first time, this study established a model to discriminate seaweed species using a multi-element fingerprinting approach for species identification. Twenty-nine elements derived from seaweeds were analyzed. Chemometrics showed that seaweed samples could be well separated by the established multi-element fingerprints, of which Ag, Mn, Sr, and K were the most important variables for discrimination. Furthermore, the present study proposed an innovative risk-benefit assessment strategy for seaweeds that considers both risks and benefits, developing a novel risk-benefit assessment model from both dietary and medicinal perspectives for the first time. Our innovative strategy was well-conceived to accurately and effectively differentiate seaweeds based on species and scientifically evaluate both benefits and risks associated with seaweeds. This strategy is poised to offer invaluable insights into the sustainable growth of the seaweed sector and to bolster public health initiatives, ensuring a robust and forward-looking approach to both industry and healthcare advancements.

Optimizing extraction methods by a comprehensive experimental approach and characterizing polyphenol compositions of Ecklonia radiata

Brown seaweed Ecklonia radiata harbors valuable polyphenols, notably phlorotannins, prized for their health benefits. This study optimized phlorotannin extraction via conventional solvent extraction and ultrasound-assisted extraction methods, utilizing variable concentrations of ethanol. Employing fractional factorial designs, key variables were identified. Steepest ascent/descent method and central composite rotatable designs refined optimal conditions, enhancing phlorotannin and polyphenol yields, and antioxidant capacities. Under optimized conditions, phlorotannin contents reached 2.366 ± 0.01 and 2.596 ± 0.04 PGE mg/g, total polyphenol contents peaked at 10.223 ± 0.03 and 10.836 ± 0.02 GAE mg/g. Robust antioxidant activity was observed: DPPH and OH radical scavenging capacities measured 27.891 ± 0.06 and 17.441 ± 0.08 TE mg/g, and 37.498 ± 1.12 and 49.391 ± 0.82 TE mg/g, respectively. Reducing power capacities surged to 9.016 ± 0.02 and 28.110 ± 0.10 TE mg/g. Liquid chromatography-mass spectrometry (LC-MS) and high-performance liquid chromatography (HPLC) analyses revealed enriched antioxidant compounds. Variations in polyphenol profiles were noted, potentially influencing antioxidant capacity nuances. This study illuminated the potential of E. radiata potential as a polyphenol source and offers optimized extraction methods poised to benefit various industries.

Comprehensive Nutritional and Functional Characterization of Novel Mycoprotein Derived from the Bioconversion of Durvillaea spp

This study aimed, for the first time, to determine the nutritional composition, beta-glucan and ergosterol contents, phenolic compound composition, and biological and functional activities of a novel mycoprotein produced through a bioconversion process of Durvillaea spp., a brown seaweed. An untargeted metabolomics approach was employed to screen metabolites and annotate molecules with nutraceutical properties. Two products, each representing a distinct consortia of co-cultured fungi, named Myco 1 and Myco 2, were analysed in this study. These consortia demonstrated superior properties compared to those of Durvillaea spp., showing significant increases in total protein (~238%), amino acids (~219%), and β-D-glucans (~112%). The protein contains all essential amino acids, a low fatty acid content, and exhibits high antioxidant activity (21.5-25.5 µmol TE/g). Additionally, Myco 2 exhibited the highest anti-alpha-glucosidase activity (IC50 = 16.5 mg/mL), and Myco 1 exhibited notable anti-lipase activity (IC50 = 10.5 mg/mL). Among the 69 top differentially abundant metabolites screened, 8 nutraceutical compounds were present in relatively high concentrations among the identified mycoproteins. The proteins and polysaccharides in the mycoprotein may play a crucial role in the formation and stabilization of emulsions, identifying it as a potent bioemulsifier. In conclusion, the bioconversion of Durvillaea spp. results in a mycoprotein with high-quality protein, significant nutritional and functional value, and prebiotic and nutraceutical potential due to the production of unique bioactive compounds.

Comparison of phenolic composition in Australian-grown date fruit (Phoenix dactylifera L.) seeds from different varieties and ripening stages

In this research, different seeds of Australian-grown date palm (Phoenix dactylifera L.) were studied to evaluate the antioxidant potential and analyze their phenolic constituents. Phenolic compounds were extracted from seeds of various Australian-grown date varieties at different ripening stages. Eight varieties of date seeds (Zahidi, Medjool, Deglet nour, Thoory, Halawi, Barhee, Khadrawy, and Bau Strami) at three ripening stages (Kimri, Khalal, and Tamar) were investigated in this study. Date seeds at Khalal (9.87-16.93 mg GAE/g) and Tamar (9.20-27.87 mg GAE/g) stages showed higher total phenolic content than those at Kimri stage (1.81-5.99 mg GAE/g). For antioxidant assays like DPPH, FRAP, ABTS, RAP, FICA, and TAC, date seeds at Khalal and Tamar stages also showed higher antioxidant potential than Kimri stage. However, date seeds at Kimri stage (55.24-63.26 mg TE/g) expressed higher radical scavenging activity than Khalal (13.58-51.88 mg TE/g) and Tamar (11.06-50.92 mg TE/g) stages. Phenolic compounds were characterized using LC-ESI-QTOF-MS/MS, revealing the presence of 37 different phenolic compounds, including 8 phenolic acids, 18 flavonoids, and 11 other phenolic compounds. Further, phenolic compounds were quantified using LC-DAD, revealing that Zahidi variety of date seeds exhibited the highest content during the Kimri stage. In contrast, during the Khalal and Tamar stages, Deglet nour and Medjool date seeds displayed higher concentrations of phenolic compounds. The results indicated an increase in phenolic content in date seeds after the Kimri stage, with significant variations observed among different date varieties.

Optimization of Ultrasonic Extraction Parameters for the Recovery of Phenolic Compounds in Brown Seaweed: Comparison with Conventional Techniques

Seaweed, in particular, brown seaweed, has gained research interest in the past few years due to its distinctive phenolic profile that has a multitude of bioactive properties. In order to obtain the maximum extraction efficiency of brown seaweed phenolic compounds, Response Surface Methodology was utilized to optimize the ultrasound-assisted extraction (UAE) conditions such as the amplitude, time, solvent:solid ratio, and NaOH concentration. Under optimal conditions, UAE had a higher extraction efficiency of free and bound phenolic compounds compared to conventional extraction (stirred 16 h at 4 °C). This led to higher antioxidant activity in the seaweed extract obtained under UAE conditions. The profiling of phenolic compounds using LC-ESI-QTOF-MS/MS identified a total of 25 phenolics with more phenolics extracted from the free phenolic extraction compared to the bound phenolic extracts. Among them, peonidin 3-O-diglucodise-5-O-glucoside and hesperidin 5,7-O-diglucuronide are unique compounds that were identified in P. comosa, E. radiata and D. potatorum, which are not reported in plants. Overall, our findings provided optimal phenolic extraction from brown seaweed for research into employing brown seaweed as a functional food.

In vitro digestion and colonic fermentation of phenolic compounds and their antioxidant potential in Australian beach-cast seaweeds

Beach-cast seaweed has recently garnered attention for its nutrient-rich composition, including proteins, carbohydrates, vitamins, minerals, and phytochemicals. This study focuses on the phenolic content and antioxidant potential of five Australian beach-cast seaweed species during in vitro digestion and colonic fermentation. The bioaccessibility of the selected phenolic compounds was estimated and short chain fatty acids (SCFAs) production was determined. Cystophora sp., showed a notable increase in phenolic content (23.1 mg GAE/g) and antioxidant capacity (0.42 mg CE/g) during the intestinal and gastric phases of in vitro digestion. Durvillaea sp. demonstrated a significant release of flavonoids (0.35 mg QE/g), while Phyllosphora comosa released high levels of tannins (0.72 mg CE/g) during the intestinal phase. During colonic fermentation, P. comosa released the highest levels of phenolic compounds (4.3 mg GAE/g) after 2 h, followed by an increase in flavonoids (0.15 mg QE/g), tannins (0.07 mg CE/g), and antioxidant activity (DPPH: 0.12 mg CE/g; FRAP: 0.61 mg CE/g) after 4 h. Moreover, P. comosa released a considerable amount of phenolic compounds during both in vitro digestion and colonic fermentation. All species consistently released phenolic compounds throughout the study. Phloroglucinol, gallic acid, and protocatechuic acid were identified as the most bioaccessible phenolic compounds in all five Australian beach-cast seaweeds in the in vitro digestion. Nevertheless, compound levels declined during the colonic fermentation phase due to decomposition and fermentation by gut microbiota. With regard to SCFAs, P. comosa displayed elevated levels of acetic (0.51 mmol/L) and propionic acid (0.36 mmol/L) at 2 h, while Durvillaea sp. showed increased butyric (0.42 mmol/L) and valeric (0.26 mmol/L) production acid after 8 h. These findings suggest that seaweed such as Cystophora sp., Durvillaea sp., and P. comosa are promising candidates for food fortification or nutraceutical applications, given their rich phenolic content and antioxidant properties that potentially offer gut health benefits.

Seaweed and Seaweed-Based Functional Metabolites as Potential Modulators of Growth, Immune and Antioxidant Responses, and Gut Microbiota in Fish

Seaweed, also known as macroalgae, represents a vast resource that can be categorized into three taxonomic groups: Rhodophyta (red), Chlorophyta (green), and Phaeophyceae (brown). They are a good source of essential nutrients such as proteins, minerals, vitamins, and omega-3 fatty acids. Seaweed also contains a wide range of functional metabolites, including polyphenols, polysaccharides, and pigments. This study comprehensively discusses seaweed and seaweed-derived metabolites and their potential as a functional feed ingredient in aquafeed for aquaculture production. Past research has discussed the nutritional role of seaweed in promoting the growth performance of fish, but their effects on immune response and gut health in fish have received considerably less attention in the published literature. Existing research, however, has demonstrated that dietary seaweed and seaweed-based metabolite supplementation positively impact the antioxidant status, disease resistance, and stress response in fish. Additionally, seaweed supplementation can promote the growth of beneficial bacteria and inhibit the proliferation of harmful bacteria, thereby improving gut health and nutrient absorption in fish. Nevertheless, an important balance remains between dietary seaweed inclusion level and the resultant metabolic alteration in fish. This review highlights the current state of knowledge and the associated importance of continued research endeavors regarding seaweed and seaweed-based functional metabolites as potential modulators of growth, immune and antioxidant response, and gut microbiota composition in fish.

Improving potential strategies for biological activities of phlorotannins derived from seaweeds

Seaweeds have garnered considerable attention due to their capacity to serve as exceptional reservoirs of numerous bioactive metabolites possessing substantial chemical and biological significance. .Phlorotannins constitute a significant class of natural polyphenols originating from brown seaweeds, featuring a broad spectrum of bioactive attributes and demonstrating potential applicability across various sectors. The potential health advantages associated with phlorotannins, particularly concerning the prevention of conditions linked to oxidative stress, such as inflammation, diabetes, and allergies, have generated substantial interest within the food and pharmaceutical industries. Nevertheless, current research remains insufficient in providing a comprehensive understanding of their absorption, as comparisons drawn with their terrestrial counterparts remain speculative. It is commonly presumed that phenolic compounds, including phlorotannins, face challenges due to their limited solubility, instability, and extensive metabolism, all of which restrict their bioavailability. In order to circumvent these limitations and amplify their utility as components of medicinal formulations or healthcare products, researchers have explored various strategies, including the encapsulation or integration of phlorotannins into nano-/micro-particles or advanced drug delivery systems. This review offers a thorough exploration of the structural and biological attributes of phlorotannins and furnishes insights into potential strategies showing promise for their effective utilization in preclinical and clinical applications.