Considerations on the use of enzyme-assisted extraction in combination with pressurized liquids to recover bioactive compounds from algae

Antioxidant and Antidiabetic Properties of Phlorotannins from Ascophyllum nodosum Seaweed Extracts

Seaweeds have gained considerable attention in recent years due to their potential health benefits and high contents of bioactive compounds. This review focuses on the exploration of seaweed's health-promoting properties, with particular emphasis on phlorotannins, a class of bioactive compounds known for their antioxidant and antidiabetic properties. Various novel and ecofriendly extraction methods, including solid-liquid extraction, ultrasound-assisted extraction, and microwave-assisted extraction are examined for their effectiveness in isolating phlorotannins. The chemical structure and isolation of phlorotannins are discussed, along with methods for their characterization, such as spectrophotometry, nuclear magnetic resonance, Fourier transform infrared spectroscopy, and chromatography. Special attention is given to the antioxidant activity of phlorotannins. The inhibitory capacities of polyphenols, specifically phlorotannins from Ascophyllum nodosum against digestive enzymes, such as α-amylase and α-glucosidase, are explored. The results suggest that polyphenols from Ascophyllum nodosum seaweed hold significant potential as enzyme inhibitors, although the inhibitory activity may vary depending on the extraction conditions and the specific enzyme involved. In conclusion, seaweed exhibits great potential as a functional food ingredient for promoting health and preventing chronic diseases. Overall, this review aims to condense a comprehensive collection of high-yield, low-cost, and ecofriendly extraction methods for obtaining phlorotannins with remarkable antioxidant and antidiabetic capacities.

Applications of Antioxidant Secondary Metabolites of Sargassum spp

Sargassum is one of the largest and most diverse genus of brown seaweeds, comprising of around 400 taxonomically accepted species. Many species of this genus have long been a part of human culture with applications as food, feed, and remedies in folk medicine. Apart from their high nutritional value, these seaweeds are also a well-known reservoir of natural antioxidant compounds of great interest, including polyphenols, carotenoids, meroterpenoids, phytosterols, and several others. Such compounds provide a valuable contribution to innovation that can translate, for instance, into the development of new ingredients for preventing product deterioration, particularly in food products, cosmetics or biostimulants to boost crops production and tolerance to abiotic stress. This manuscript revises the chemical composition of Sargassum seaweeds, highlighting their antioxidant secondary metabolites, their mechanism of action, and multiple applications in fields, including agriculture, food, and health.

Pressurized Liquid Extraction for the Recovery of Bioactive Compounds from Seaweeds for Food Industry Application: A Review

Seaweeds are an underutilized food in the Western world, but they are widely consumed in Asia, with China being the world’s larger producer. Seaweeds have gained attention in the food industry in recent years because of their composition, which includes polysaccharides, lipids, proteins, dietary fiber, and various bioactive compounds such as vitamins, essential minerals, phenolic compounds, and pigments. Extraction techniques, ranging from more traditional techniques such as maceration to novel technologies, are required to obtain these components. Pressurized liquid extraction (PLE) is a green technique that uses high temperatures and pressure applied in conjunction with a solvent to extract components from a solid matrix. To improve the efficiency of this technique, different parameters such as the solvent, temperature, pressure, extraction time and number of cycles should be carefully optimized. It is important to note that PLE conditions allow for the extraction of target analytes in a short-time period while using less solvent and maintaining a high yield. Moreover, the combination of PLE with other techniques has been already applied to extract compounds from different matrices, including seaweeds. In this way, the combination of PLE-SFE-CO2 seems to be the best option considering both the higher yields obtained and the economic feasibility of a scaling-up approximation. In addition, the food industry is interested in incorporating the compounds extracted from edible seaweeds into food packaging (including edible coating, bioplastics and bio-nanocomposites incorporated into bioplastics), food products and animal feed to improve their nutritional profile and technological properties. This review attempts to compile and analyze the current data available regarding the application of PLE in seaweeds to determine the use of this extraction technique as a method to obtain active compounds of interest for food industry application.

Bioprospecting of Targeted Phenolic Compounds of Dictyota dichotoma, Gongolaria barbata, Ericaria amentacea, Sargassum hornschuchii and Ellisolandia elongata from the Adriatic Sea Extracted by Two Green Methods

The content of bioactive compounds in four brown and one red algae from the Adriatic Sea (Dictyota dichotoma, Gongolaria barbata, Ericaria amentacea, Sargassum hornschuchii and Ellisolandia elongata) is explored. The efficiency of two different extraction methods viz. ultrasound-assisted extraction (UAE) and matrix solid-phase dispersion (MSPD) to obtain the extracts rich in phenolic compounds was compared. The effect of the extraction solvent to modulate the phenolic profile was assessed. In general, the mixture ethanol/water in an isovolumetric proportion showed the best results. The total phenolic content (TPC) and antioxidant activity (AA), as well as the individual polyphenolic profile, were evaluated for five target algae. TPC values ranged between 0.2 mg GAE/g (for E. elongata) and 38 mg GAE/g (for S. hornschuchii). Regarding the quantification of individual polyphenols by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis, the presence of a high number of hydroxybenzoic acid derivatives (mainly of 3- and 4-hydroxybenzoic acids) in all species was noted. In G. barbata their concentrations reached up to 500 mg/kg. IC50 values (ABTS assay) ranged between 44 mg/L (for S. hornschuchii) and 11,040 mg/L (for E. elongata). This work contributes to the in-depth characterization of these little-explored algae, showing their potential as a natural source of phenolic compounds.

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.

Methodological Optimization of Supercritical Fluid Extraction of Valuable Bioactive Compounds from the Acidophilic Microalga Coccomyxa onubensis

Microalgae grow in diverse environments and possess a great biotechnological potential as they contain useful bioactive compounds. These bioactive compounds can be obtained by selective and energy-efficient extraction methods. Various industries are using the supercritical fluid extraction (SFE) method to extract these valuable bioactive compounds. Hence, for the first time, we evaluated the effects of SFE on the recovery of bioactive and antioxidant compounds using Coccomyxa onubensis, a eukaryotic acidophilic microalga of potential relevance which can be used in the field of nutraceutical and functional foods. It was isolated from the Tinto River (Pyritic Belt, Huelva, Spain), a mining region in Spain. Variables such as extraction yield, lutein purity (LP) and recovery (LR), total phenols, and antioxidant capacity (Trolox equivalents antioxidant capacity method) were studied using a Box–Behnken design based on a response surface methodology along with the overall extraction curve fitted to a spline linear model. The effects of temperature (30, 50, and 70 °C), pressure (25, 40, and 55 MPa), and the percentage of co-solvent (0, 25%, and 50% v/v ethanol) on SFE were analyzed, resulting in the co-solvent and temperature as the most significant factors followed by the pressure. Under 70 °C, 40 MPa, and 50% v/v ethanol, C. onubensis reached a maximum of 66.98% of LR. The extracts were richest in total phenols and showed the maximum antioxidant activity (36.08 mg GAEs/g extracts and 2.237 mmol TE/g extracts, respectively) under similar pressure and co-solvent percentage values and different temperatures (30 and 70 °C, respectively). The extracts obtained in this study may have potential applications in the food, nutraceutical, and cosmetic industries. SFE is a highly efficient method to valorize microorganisms living in extreme environments, which are so far unexplored using green extraction methods.

Purification and Identification of an ACE-Inhibitory Peptide from Gracilaria tenuistipitata Protein Hydrolysates

Edible marine species are valuable sources of bioactive peptides. This study investigated the ACE-inhibitory activity of protein hydrolysates from the red algae Gracilaria tenuistipitata. Fifteen groups of protein hydrolysates were prepared by a two-step enzymatic hydrolysis of G. tenuistipitata: initial hydrolysis with several glycolytic enzymes, followed by three separate proteolytic reactions (Alcalase, Neutrase and Flavourzyme) for 2–10 h. Results showed that the hydrolysate GTN4H had the highest ACE-inhibitory activity in vitro. Furthermore, oral administration of GTN4H significantly reduced systolic blood pressure in spontaneously hypertensive rats. Fraction A derived from GTN4H displayed the highest ACE-inhibitory activity among fractions. Further purification of fraction A by RP-HPLC obtained a purified peptide (MW: 1776 Da) with 17 amino acids and 95.4% ACE-inhibitory activity.

Marine algal flavonoids and phlorotannins; an intriguing frontier of biofunctional secondary metabolites

Algae are the oldest representatives of the plant world with reserves exceeding hundreds of millions of tons in the world's oceans. Currently, a growing interest is placed toward the use of algae as feedstocks for obtaining numerous natural products. Algae are a rich source of polyphenols that possess intriguing structural diversity. Among the algal polyphenols, phlorotannins, which are unique to brown seaweeds, and have immense value as potent modulators of biochemical processes linked to chronic diseases. In algae, flavonoids remain under-explored compared to other categories of polyphenols. Both phlorotannins and flavonoids are inclusive of compounds indicating a wide structural diversity. The present paper reviews the literature on the ecological significance, biosynthesis, structural diversity, and bioactivity of seaweed phlorotannins and flavonoids. The potential implementation of these chemical entities in functional foods, cosmeceuticals, medicaments, and as templates in drug design are described in detail, and perspectives are provided to tackle what are perceived to be the most momentous challenges related to the utilization of phlorotannins and flavonoids. Moving beyond: industrial biotechnology applications, metabolic engineering, total synthesis, biomimetic synthesis, and chemical derivatization of phlorotannins and flavonoids could broaden the research perspectives contributing to the health and economic up-gradation.

Aquatic Phlorotannins and Human Health: Bioavailability, Toxicity, and Future Prospects

Medicinal chemists and pharmacognosists have relied on terrestrial sources for bioactive phytochemicals to manage and treat disease conditions. However, minimal interest is given to sea life, especially macroalgae and their inherent phytochemical reserves. Phlorotannins are a special class of phytochemicals mainly predominant in brown algae of marine and estuarine habitats. Phlorotannins are formed through the polymerization of phloroglucinol residues and derivatives via the polyketide (acetate–malonate) pathway. Studies over the past decades have implicated phlorotannins with several bioactivities, including anti-herbivory, antioxidants, anti-inflammatory, anti-microbial, anti-proliferative, anti-diabetic, radio-protective, adipogenic, anti-allergic, and anti-human immunodeficiency virus (anti-HIV) properties. All these activities are reflected in their applications as nutraceuticals and cosmeceutical agents. This article reviews the chemical composition of phlorotannins, their biological roles, and their applications. Moreover, very few studies on phlorotannin bioavailability, safety, and toxicity have been thoroughly reviewed. The paper concludes by suggesting exciting research questions for further studies.

Pressurized Liquid Extraction Combined with Enzymatic-Assisted Extraction to Obtain Bioactive Non-Extractable Polyphenols from Sweet Cherry (Prunus avium L.) Pomace

Sweet cherry generates large amounts of by-products within which pomace can be a source of bioactive phenolic compounds. Commonly, phenolic compounds have been obtained by conventional extraction methodologies. However, a significant fraction, called non-extractable polyphenols (NEPs), stays held in the conventional extraction residues. Therefore, in the present work, the release of NEPs from cherry pomace using pressurized liquid extraction (PLE) combined with enzyme-assisted extraction (EAE) using Promod^TM enzyme is investigated for the first time. In order to study the influence of temperature, time, and pH on the NEPs extraction, a response surface methodology was carried out. PLE-EAE extracts displayed higher TPC (75 ± 8 mg GAE/100 g sample) as well as, PA content, and antioxidant capacity than the extracts obtained by PLE (with a TPC value of 14 ± 1 mg GAE/100 g sample) under the same extraction conditions, and those obtained by conventional methods (TPC of 8.30 ± 0.05 mg GAE/100 g sample). Thus, PLE-EAE treatment was more selective and sustainable to release NEPs from sweet cherry pomace compared with PLE without EAE treatment. Besides, size-exclusion chromatography profiles showed that PLE-EAE allowed obtaining NEPs with higher molecular weight (>8000 Da) than PLE alone.

An Overview on Effects of Processing on the Nutritional Content and Bioactive Compounds in Seaweeds

The effect of the different processing technologies and the extraction techniques on the bioactive compounds and nutritional value of seaweeds is reviewed in this study. This work presents and discusses the main seaweeds treatments such as drying, heating, and culinary treatments, and how they affect their nutritional value, the bioactive compounds, and antioxidant capacity. Some examples of traditional and green extraction technologies for extracting seaweeds bioactive components are also presented. The last trends and research on the development of seaweed-based food products is also covered in this review. The use of environmentally friendly extraction procedures, as well as the development of new healthy seaweed-based foods, is expected to grow in the near future.

Screening of Bioactive Properties in Brown Algae from the Northwest Iberian Peninsula

Algae are an underexploited source of natural bioactive compounds in Western countries, so an increasing interest in the valorization of these marine organisms has emerged in recent years. In this work, the effect of extracting solvent on the extraction yield, phenolic content, antioxidant capacity, and antimicrobial activity of nine brown macroalgae species (Ascophyllum nodosum, Himanthalia elongata, Undaria pinnatifida, Pelvetia canaliculata, Saccharina latissima, Bifurcaria bifurcata, Laminaria ochroleuca, Sargassum muticum, and Fucus spiralis) was assessed. Total phenolic content (TPC) and the antioxidant properties of extracts by different assays: radical scavenging activity (DPPH-RSA) and ferric reducing antioxidant power (FRAP) were performed. The antimicrobial activity of extracts was studied against six different foodborne microorganisms: Staphylococcus aureus, Staphylococcus epidermidis, Bacillus cereus, Escherichia coli, Salmonella enteritidis, and Pseudomonas aeruginosa. The highest extraction yield was achieved in ethanolic extracts. However, the highest TPC and FRAP values were obtained on the ethyl acetate extracts, especially from A. nodosum. Concerning algal species, the highest TPC and FRAP values were found in A. nodosum, while the highest DPPH-RSA values were achieved in the hexane extracts of B. bifurcata. The antimicrobial activity of algal extracts varied according to the solvent and alga selected, suggesting the species- and solvent-dependent behavior of this property, with B. bifurcata extracts showing the highest results for a wide range of bacteria. Our results provide insight on the characterization of widespread brown algae in the coasts of the North-Western region of the Iberian Peninsula, reflecting multiple health-enhancing properties which may lead to their exploitation in food, pharmacological, and cosmetic industries.

Exploitation of Marine Molecules to Manage Alzheimer's Disease

Neurodegenerative diseases are sociosanitary challenges of today, as a result of increased average life expectancy, with Alzheimer’s disease being one of the most prevalent. This pathology is characterized by brain impairment linked to a neurodegenerative process culminating in cognitive decline and behavioral disorders. Though the etiology of this pathology is still unknown, it is usually associated with the appearance of senile plaques and neurofibrillary tangles. The most used prophylaxis relies on anticholinesterase drugs and NMDA receptor antagonists, whose main action is to relieve symptoms and not to treat or prevent the disease. Currently, the scientific community is gathering efforts to disclose new natural compounds effective against Alzheimer’s disease and other neurodegenerative pathologies. Marine natural products have been shown to be promising candidates, and some have been proven to exert a high neuroprotection effect, constituting a large reservoir of potential drugs and nutraceutical agents. The present article attempts to describe the processes of extraction and isolation of bioactive compounds derived from sponges, algae, marine bacteria, invertebrates, crustaceans, and tunicates as drug candidates against AD, with a focus on the success of pharmacological activity in the process of finding new and effective drug compounds.

Maximizing the Antioxidant Capacity of Padina pavonica by Choosing the Right Drying and Extraction Methods

Marine algae are becoming an interesting source of biologically active compounds with a promising application as nutraceuticals, functional food ingredients, and therapeutic agents. The effect of drying (freeze-drying, oven-drying, and shade-drying) and extraction methods (shaking at room temperature, shaking in an incubator at 60 °C, ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE)) on the total phenolics content (TPC), total flavonoids content (TFC), and total tannins content (TTC), as well as antioxidant capacity of the water/ethanol extracts from Padina pavonica were investigated. The TPC, TFC, and TTC values of P. pavonica were in the range from 0.44 ± 0.03 to 4.32 ± 0.15 gallic acid equivalents in mg/g (mg GAE/g) dry algae, from 0.31 ± 0.01 to 2.87 ± 0.01 mg QE/g dry algae, and from 0.32 ± 0.02 to 10.41 ± 0.62 mg CE/g dry algae, respectively. The highest TPC was found in the freeze-dried sample in 50% ethanol, extracted by MAE (200 W, 60 °C, and 5 min). In all cases, freeze-dried samples extracted with ethanol (both 50% and 70%) had the higher antioxidant activity, while MAE as a green option reduces the extraction time without the loss of antioxidant activity in P. pavonica.

The Use of Invasive Algae Species as a Source of Secondary Metabolites and Biological Activities: Spain as Case-Study

In the recent decades, algae have proven to be a source of different bioactive compounds with biological activities, which has increased the potential application of these organisms in food, cosmetic, pharmaceutical, animal feed, and other industrial sectors. On the other hand, there is a growing interest in developing effective strategies for control and/or eradication of invasive algae since they have a negative impact on marine ecosystems and in the economy of the affected zones. However, the application of control measures is usually time and resource-consuming and not profitable. Considering this context, the valorization of invasive algae species as a source of bioactive compounds for industrial applications could be a suitable strategy to reduce their population, obtaining both environmental and economic benefits. To carry out this practice, it is necessary to evaluate the chemical and the nutritional composition of the algae as well as the most efficient methods of extracting the compounds of interest. In the case of northwest Spain, five algae species are considered invasive: Asparagopsis armata, Codium fragile, Gracilaria vermiculophylla, Sargassum muticum, and Grateulopia turuturu. This review presents a brief description of their main bioactive compounds, biological activities, and extraction systems employed for their recovery. In addition, evidence of their beneficial properties and the possibility of use them as supplement in diets of aquaculture animals was collected to illustrate one of their possible applications.

In vitro neuroprotective potential of terpenes from industrial orange juice by-products

Citrus sinensis (orange) by-products represent one of the most abundant citric residues from orange juice industrial production, and are a promising source of health-promoting compounds like terpenes. In this work, different extraction solvents have been employed to increase terpene extraction yield and selectivity from this orange juice by-product. A set of bioactivity assays including enzymatic (acetylcholinesterase (AChE), butylcholinesterase (BChE) and lipoxygenase (LOX)) as well as antioxidant (ABTS, reactive oxygen species (ROS) and reactive nitrogen species (RNS)) activity tests have been applied to investigate the neuroprotective potential of these compounds. New fluorescence-based methodologies were developed for AChE and BChE assays to overcome the drawbacks of these tests when used in vitro to determine the anticholinergic activity of colored extracts. Comprehensive phytochemical profiling based on gas chromatography coupled to quadrupole time of flight mass spectrometry (GC-qTOF-MS) analysis showed ahigh content of mono- and sesquiterpenes in the extracts obtained with ethyl acetate, whereas n-heptane extracts exhibited a large amount of triterpenes and carotenoids. From a neuroprotective activity point of view, ethyl acetate extract is the most promising due to its anticholinergic activity and antioxidant capacity. Finally, a multivariate data analysis revealed a good correlation between some monoterpenes (e.g. nerol or limonene) and the antioxidant capacity of the natural extract, while a group of sesquiterpenes (e.g.δ-Cadinene or nootkatone) showed correlation with the observed AChE, BChE and LOX inhibition capacity. Hydrocarbons mono- and sesquiterpenoids reveal high capacity in vitro to cross the blood-brain barrier (BBB).

Phlorotannins: From isolation and structural characterization, to the evaluation of their antidiabetic and anticancer potential

Phlorotannins are phenolic characteristic compounds of brown seaweeds that are only constituted by phloroglucinol (1,3,5-trihydroxybenzene). They are chain- and net-like structures of diverse molecular weights and have been widely identified in Ecklonia, Eisenia, and Ishige species. Since the time they were discovered in the '70 s, phlorotannins have been suggested as a main factor responsible for the antimicrobial activities attributed to algae extracts. Currently, cumulative in vitro and in vivo research evidence the diverse bioactivities of phlorotannin extracts -such as antidiabetic, anticancer, and antibacterial- pointing out their potential pharmacological and food applications. However, metabolomic studies and clinical trials are scarce, and thus many phlorotannins health-beneficial effects in humans are not yet confirmed. This article reviews recent studies assessing the antidiabetic and anticancer activities of phlorotannins. Particularly, their potential to prevent and control the progression of these non-communicable diseases is discussed, considering in vitro and animal studies, as well as clinical interventions. In contrast to other approaches, we only included investigations with isolated phlorotannins or phlorotannin-rich extracts. Thus, phlorotannin extraction, purification and characterization procedures are briefly addressed. Overall, although considerable research showing the antidiabetic and anticancer potential of phlorotannins is now available, further clinical trials are still necessary to conclusively demonstrate the efficacy of these compounds as adjuvants for diabetes and cancer prevention or treatment.

Main bioactive phenolic compounds in marine algae and their mechanisms of action supporting potential health benefits

Given the growing tendency of consumers to choose products with natural ingredients, food industries have directed scientific research in this direction. In this regard, algae are an attractive option for the research, since they can synthesize a group of secondary metabolites, called phenolic compounds, associated with really promising properties and bioactivities. The objective of this work was to classify the major phenolic compounds, compare the effectiveness of the different extractive techniques used for their extraction, from traditional systems (like heat assisted extraction) to the most advance ones (such as ultrasound, microwave or supercritical fluid extraction); the available methods for identification and quantification; the stability of the enriched extract in phenolic compounds and the main bioactivities described for these secondary metabolites, to offer an overview of the situation to consider if it is possible and/or convenient an orientation of phenolic compounds from algae towards an industrial application.

Phlorotannins from Fucus vesiculosus: Modulation of Inflammatory Response by Blocking NF-κB Signaling Pathway

Due to their large spectrum of bioactive properties, much attention has recently been drawn to phlorotannins-i.e., phenolic compounds characteristic from brown macroalgae. This study aimed to evaluate the antioxidant and anti-inflammatory properties of F. vesiculosus phlorotannin extracts and purified fractions. Overall, the crude extract and its ethyl acetate fraction (EtOAc) showed good radical scavenging activity, particularly towards nitric oxide (NO•). Subsequent subfractions of EtOAc (F1 to F9) with different molecular weights were then shown to inhibit lipopolysaccharide-induced NO• production in macrophages, with stronger effects being observed for fractions of lower MWs. Of the three intracellular markers analyzed, inducible NO• synthase showed the highest sensitivity to almost all the phlorotannin-rich samples, followed by interleukin 1β and cyclooxygenase 2, which was only inhibited by F2. Furthermore, this subfraction inhibited the phosphorylation and degradation of inhibitory protein κBα, thus preventing the activation of NF-κB and blocking the inflammatory cascade at the transcriptional level. This sample was characterized by the presence of a major compound with a deprotonated molecular ion at m/z 507 with a fragmentation pattern coherent with that of a phlorotannin derivative. Overall, this work unveiled some of the mechanistic aspects behind the anti-inflammatory capacity of phlorotannins from F. vesiculosus, endorsing its use as a possible natural source of anti-inflammatory compounds.

Seaweed-based natural ingredients: Stability of phlorotannins during extraction, storage, passage through the gastrointestinal tract and potential incorporation into functional foods

Adding value to seaweed by extracting their different bioactive compounds and incorporating them into foods represent an interesting and strategic approach to diversify the functional foods offer. However, once harvested, fresh seaweed must overcome a sequence of crucial steps to confer their biological activity. Pre-processing operations and extraction processes, as well as long-term storage, play important roles in improving or decreasing the phlorotannins content. In their way to the gut (biological target), phlorotannins are exposed to the human gastrointestinal tract (GIT), where the physiological pH and digestive enzymes can significantly affect the phlorotannins' stability and thus, alter their biological activity. Besides, the subsequent incorporation into foodstuffs could be limited due to sensory issues, as tannins have been associated with astringency and bitter taste, and thus effective phlorotannins doses may negatively affect the sensory attributes of foods. These drawbacks expose the need of applying smart strategies to develop a final product providing the necessary protective mechanisms to maintain the active molecular form of phlorotannins up to the consumption time, also controlling their release upon arrival to the gut. In this context, the impact of these technological processes (from pre-processing to the passage through the GIT) on phlorotannins stability, as well as the innovative developed approaches to overcome these issues will be deeply discussed in this review. Besides, recent findings related to the phlorotannins' health benefits will be pointed out. Special attention on the potential incorporation of phlorotannins into functional foods will be also put it on.

Emerging Technologies for the Extraction of Marine Phenolics: Opportunities and Challenges

Natural phenolic compounds are important classes of plant, microorganism, and algal secondary metabolites. They have well-documented beneficial biological activities. The marine environment is less explored than other environments but have huge potential for the discovery of new unique compounds with potential applications in, e.g., food, cosmetics, and pharmaceutical industries. To survive in a very harsh and challenging environment, marine organisms like several seaweed (macroalgae) species produce and accumulate several secondary metabolites, including marine phenolics in the cells. Traditionally, these compounds were extracted from their sample matrix using organic solvents. This conventional extraction method had several drawbacks such as a long extraction time, low extraction yield, co-extraction of other compounds, and usage of a huge volume of one or more organic solvents, which consequently results in environmental pollution. To mitigate these drawbacks, newly emerging technologies, such as enzyme-assisted extraction (EAE), microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), pressurized liquid extraction (PLE), and supercritical fluid extraction (SFE) have received huge interest from researchers around the world. Therefore, in this review, the most recent and emerging technologies are discussed for the extraction of marine phenolic compounds of interest for their antioxidant and other bioactivity in, e.g., cosmetic and food industry. Moreover, the opportunities and the bottleneck for upscaling of these technologies are also presented.

Application of Box-Behnken Design and Desirability Function for Green Prospection of Bioactive Compounds from Isochrysis galbana

A microalga, Isochrysis galbana, was chosen in this study for its potent natural antioxidant composition. A broad bioactive compounds spectrum such as carotenoids, fatty acid polyunsaturated (PUFA), and antioxidant activity are described with numerous functional properties. However, most of the optimization of extraction use toxic solvents or consume a lot of it becoming an environmental concern. In this research, a Box-Behnken design with desirability function was used to prospect the bioactive composition by supercritical fluid extraction (SFE) after performing the kinetics curve to obtain the optimal extraction time minimizing operational costs in the process. The parameters studied were: pressure (20–40 MPa), temperature (40–60 °C), and co-solvent (0–8% ethanol) with a CO2 flow rate of 7.2 g/min for 120 min. The response variables evaluated in I. galbana were extraction yield, carotenoids content and recovery, total phenols, antioxidant activity (TEAC method, trolox equivalents antioxidant capacity method), and fatty acid profile and content. In general, improvement in all variables was observed using an increase in ethanol concentration used as a co-solvent (8% v/v ethanol) high pressure (40 MPa), and moderately high temperature (50 °C). The fatty acids profile was rich in polyunsaturated fatty acid (PUFA) primarily linoleic acid (C18:2) and linolenic acid (C18:3). Therefore, I. galbana extracts obtained by supercritical fluid extraction showed relevant functional ingredients for use in food and nutraceutical industries.

Advanced Technologies for the Extraction of Marine Brown Algal Polysaccharides

Over the years, brown algae bioactive polysaccharides laminarin, alginate and fucoidan have been isolated and used in functional foods, cosmeceutical and pharmaceutical industries. The extraction process of these polysaccharides includes several complex and time-consuming steps and the correct adjustment of extraction parameters (e.g., time, temperature, power, pressure, solvent and sample to solvent ratio) greatly influences the yield, physical, chemical and biochemical properties as well as their biological activities. This review includes the most recent conventional procedures for brown algae polysaccharides extraction along with advanced extraction techniques (microwave-assisted extraction, ultrasound assisted extraction, pressurized liquid extraction and enzymes assisted extraction) which can effectively improve extraction process. The influence of these extraction techniques and their individual parameters on yield, chemical structure and biological activities from the most current literature is discussed, along with their potential for commercial applications as bioactive compounds and drug delivery systems.

The Quest for Phenolic Compounds from Macroalgae: A Review of Extraction and Identification Methodologies

The current interest of the scientific community for the exploitation of high-value compounds from macroalgae is related to the increasing knowledge of their biological activities and health benefits. Macroalgae phenolic compounds, particularly phlorotannins, have gained particular attention due to their specific bioactivities, including antioxidant, antiproliferative, or antidiabetic. Notwithstanding, the characterization of macroalgae phenolic compounds is a multi-step task, with high challenges associated with their isolation and characterization, due to the highly complex and polysaccharide-rich matrix of macroalgae. Therefore, this fraction is far from being fully explored. In fact, a critical revision of the extraction and characterization methodologies already used in the analysis of phenolic compounds from macroalgae is lacking in the literature, and it is of uttermost importance to compile validated methodologies and discourage misleading practices. The aim of this review is to discuss the state-of-the-art of phenolic compounds already identified in green, red, and brown macroalgae, reviewing their structural classification, as well as critically discussing extraction methodologies, chromatographic separation techniques, and the analytical strategies for their characterization, including information about structural identification techniques and key spectroscopic profiles. For the first time, mass spectrometry data of phlorotannins, a chemical family quite exclusive of macroalgae, is compiled and discussed.

Phlorotannins from Undaria pinnatifida Sporophyll: Extraction, Antioxidant, and Anti-Inflammatory Activities

Undaria pinnatifida sporophyll (U. pinnatifida) is a major byproduct of U. pinnatifida (a brown algae) processing. Its phenolic constituents, phlorotannins, are of special interest due to their intrinsic ability to precipitate proteins. Herein, a high-temperature extraction procedure was used to isolate these biologically active compounds. The heating temperature, heating time, and extraction solvent (ethanol) concentration were examined with response surface analysis to determine the optimal conditions to achieve the maximum extraction rate. The analysis revealed the optimal conditions to be: 170 °C of heating temperature, 5.2 h of heating time, and 52% ethanol concentration for a yield of 10.7 ± 0.2 mg gallic acid equivalent/g dry weight (GAE/g DW) of sample. Compared to epigallocatechin gallate (EGCG), the extracted phlorotannins displayed higher antioxidant activity on H2O2-induced RAW 264.7 cells with improved efficiency. Furthermore, the compounds exhibited strong anti-inflammatory activity. These findings potentially can be utilized to guide development of novel functional foods and food supplements from sea-originated resources such as brown algae.

Phenolic Content of Brown Algae (Pheophyceae) Species: Extraction, Identification, and Quantification

Over the last few decades, isolations and chemical characterizations of secondary metabolites with proved biological activities have been of interest for numerous research groups across the world. Phenolics, as one of the largest and most widely distributed group of phytochemicals, have gained special attention due to their pharmacological activity and array of health-promoting benefits. Reports on phenolic potentials of marine algae, especially brown algae (Pheophyceae) that are characterized by the presence of phlorotannins, are still scarce. The aim of this review paper is to provide an overview of current knowledge about phenolic potential of different brown algae species (74 species from 7 different orders). Studies on brown algae phenolics usually involve few species, thus the focus of this review is to provide information about the phenolic potential of reported algae species and to get an insight into some issues related to the applied extraction procedures and determination/quantification methods to facilitate the comparison of results from different studies. The information provided through this review should be useful for the design and interpretation of studies investigating the brown algae as a source of valuable phytochemicals.

A multi-analytical platform based on pressurized-liquid extraction, in vitro assays and liquid chromatography/gas chromatography coupled to high resolution mass spectrometry for food by-products valorisation. Part 1: Withanolides-rich fractions from goldenberry (Physalis peruviana L.) calyces obtained after extraction optimization as case study

In this work, a multi-analytical platform that allows obtaining and characterizing high-added value compounds from natural sources is presented, with a huge potential in traditional medicine, natural products characterization, functional foods, etc. Namely, the proposed multi-analytical platform is based on the combination of pressurized liquid extraction (PLE), liquid chromatography (LC) and gas chromatography quadrupole time-of-flight mass spectrometry GC-q-TOF-MS(/MS), in vitro assays and modelling tools for guiding extraction optimization. As case study, goldenberry or cape gooseberry fruit (Physalys peruviana L.) was selected. In particular, the potential of P. peruviana calyces, an important by-product of goldenberry processing, as promising source of bioactive compounds was evaluated. Selection of the most suitable solvent for PLE was based on the Hansen solubility parameters (HSP) approach using 4β-hydroxywithanolide E (4βHWE) and withanolide E (WE) as target compounds due to their bioactive potential. A surface response methodology was further applied for the optimization of the PLE parameters: temperature (50, 100 and 150 °C) and solvent composition (% EtOH in the mixture EtOH/EtOAc). The effects of the independent variables on extraction yield, withanolides content (4βHWE and WE), total phenolic content (TPC), total flavonoids content (TFC) and antioxidant activity (EC₅₀ and TEAC) were evaluated in order to obtain withanolide-rich extracts from P. peruviana calyces. The extract obtained under optimal conditions (at 125 °C and 75% EtOH v/v) exhibited satisfactory extraction yield (14.7%) and moderate antioxidant activity (with an EC₅₀ value of 77.18 μg mL^-1 and 1.08 mM trolox g^-1), with 4βHWE and WE concentrations of 8.8 and 2.3 mg g^-1, respectively. LC-q-TOF-MS/MS analysis of the extract allowed the quantitation of 4βHWE and WE and the tentative identification of several other withanolides structures. The obtained results demonstrate the great potential of this multi-analytical approach for developing valorisation strategies of food by-products under sustainable conditions, to obtain bioactive-enriched extracts with potential medicinal or health-promoting properties.

State-of-the-Art Extraction Methodologies for Bioactive Compounds from Algal Biome to Meet Bio-Economy Challenges and Opportunities

Over the years, significant research efforts have been made to extract bioactive compounds by applying different methodologies for various applications. For instance, the use of bioactive compounds in several commercial sectors such as biomedical, pharmaceutical, cosmeceutical, nutraceutical and chemical industries, has promoted the need of the most suitable and standardized methods to extract these bioactive constituents in a sophisticated and cost-effective manner. In practice, several conventional extraction methods have numerous limitations, e.g., lower efficacy, high energy cost, low yield, etc., thus urges for new state-of-the-art extraction methodologies. Thus, the optimization along with the integration of efficient pretreatment strategies followed by traditional extraction and purification processes, have been the primary goal of current research and development studies. Among different sources, algal biome has been found as a promising and feasible source to extract a broader spectrum of bioactive compounds with point-of-care application potentialities. As evident from the literature, algal bio-products includes biofuels, lipids, polyunsaturated fatty acids, pigments, enzymes, polysaccharides, and proteins. The recovery of products from algal biomass is a matter of constant development and progress. This review covers recent advancements in the extraction methodologies such as enzyme-assisted extraction (EAE), supercritical-fluid extraction (SFE), microwave-assisted extraction (MAE) and pressurized-liquid extraction (PLF) along with their working mechanism for extracting bioactive compounds from algal-based sources to meet bio-economy challenges and opportunities. A particular focus has been given to design characteristics, performance evaluation, and point-of-care applications of different bioactive compounds of microalgae. The previous and recent studies on the anticancer, antibacterial, and antiviral potentialities of algal-based bioactive compounds have also been discussed with particular reference to the mechanism underlying the effects of these active constituents with the related pathways. Towards the end, the information is also given on the possible research gaps, future perspectives and concluding remarks.