Variations in the Composition, Antioxidant and Antimicrobial Activities of Cystoseira compressa during Seasonal Growth

Method development and validation of phloroglucinol and dieckol in Ecklonia cava using HPLC-DAD

The purpose of this study was to simultaneously analyze and validate phlorotannins, a group of functional compounds in Ecklonia cava, using HPLC-DAD. E. cava was profiled using UHPLC-Q-Orbitrap HRMS, and a total of six phlorotannin components were identified. Among these six compounds, phloroglucinol and dieckol were selected as marker components of E. cava, and a simultaneous analysis method using HPLC-DAD for phloroglucinol and dieckol was developed. Specificity, linearity, accuracy, precision, limit of detection (LOD), limit of quantification (LOQ), and matrix effect (ME) were verified using HPLC-DAD. These results complied with validation guidelines. The applicability of this simultaneous analysis method was confirmed by quantifying the contents of phloroglucinol and dieckol in E. cava samples (n = 10) purchased in Korea. This method can be used for quality control, such as standardization or determination of compounds in health functional foods containing E. cava extract.

Graphical abstract

Abiotic Factors Modulating Metabolite Composition in Brown Algae (Phaeophyceae): Ecological Impacts and Opportunities for Bioprospecting of Bioactive Compounds

Brown algae are vital structural elements and contributors to biodiversity in marine ecosystems. These organisms adapt to various environmental challenges by producing primary and secondary metabolites crucial for their survival, defense, and resilience. Besides their ecological role, these diverse metabolites have potential for biotechnological applications in industries including pharmaceuticals, cosmetics, and food. A literature review was conducted encompassing studies from 2014-2024, evaluating the effects of hydrodynamics, temperature, light, nutrients, seasonality, and salinity on the chemical profiles of various Phaeophyceae algae species. Thirty original articles spanning 69 species from the Sargassaceae, Dictyotaceae, Fucaceae, and Scytosiphonaceae families were analyzed and systematically arranged, with a focus on methodologies and key findings. This review furthers ecological discussions on each environmental factor and explores the biotechnological potential of metabolites such as polysaccharides, fatty acids, phenolics, diterpenes, and pigments. The information in this work is beneficial for metabolite bioprospecting and in vitro cultivation models as well as indoor and outdoor cultivation studies.

Comparative metabolic study of the chloroform fraction of three Cystoseira species based on UPLC/ESI/MS analysis and biological activities

This study aims to investigate the phytoconstituents of the chloroform fraction of three Cystoseira spp. namely C. myrica, C. trinodis, and C. tamariscifolia using UPLC/ESI/MS technique. The results revealed the identification of 19, 20 and 11 metabolites in C. myrica, C. trinodis, and C. tamariscifolia, respectively mainly terpenoids, flavonoids, phenolic acids and fatty acids. Also, an in vitro antioxidant study using FRAP and DPPH assays was conducted where the chloroform fraction of C. trinodis displayed the highest antioxidant activity in both assays, which would be attributed to its highest total phenolics and total flavonoids. Besides, the investigation of COX-1, α-glucosidase and α-amylase inhibitory activities were performed. Regarding C. trinodis, it showed the strongest inhibitory activity towards COX-1. Moreover, it showed potent inhibitory activity towards α-glucosidase and α-amylase enzymes. According to the molecular docking studies, the major compounds characterised showed efficient binding to the active sites of the target enzymes.

Cryptophytes as potential source of natural antimicrobials for food preservation

Cryptophytes are a promising source of bioactive compounds that have not been fully explored. This research investigated the antimicrobial activity of total phenolic compounds (TPC) and exopolysaccharides (EPS) extracted from several cryptophytes against a range of harmful foodborne bacteria and fungi. To measure the minimum inhibitory concentration (MIC) value, the broth microdilution method was used. In the antibacterial evaluation of TPC, the MIC ranged between 31.25 and 500 μg/mL, while for the antifungal activity test, it varied from 31.25 to 125 μg/mL. In the antibacterial activity test of EPS, the MIC values ranged from 125 to 1,000 μg/mL, whereas in the antifungal susceptibility test, it ranged between 62.5 and 1,000 μg/mL. The most resistant pathogen against TPC was Escherichia coli, while Campylobacter jejuni was the most susceptible. In the case of EPS, the most resistant pathogen was Salmonella Typhimurium, while Aspergillus versicolor exhibited the highest susceptibility. Overall, in terms of antimicrobial activity, TPC was more effective than EPS. Finally, the tolerance level (TL) for TPC and EPS was ≤4 in all tested samples, indicating their bactericidal/fungicidal mechanism of action. In conclusion, TPC and EPS isolated from cryptophytes demonstrated remarkable antimicrobial properties and ability to fully eradicate pathogens, and could be considered as natural preservatives in the food industry.

Volatiles from French and Croatian Sea Fennel Ecotypes: Chemical Profiles and the Antioxidant, Antimicrobial and Antiageing Activity of Essential Oils and Hydrolates

Sea fennel is a halophytic plant rich in valuable nutritional components and is characterized by pleasant organoleptic properties. While its essential oils (EOs) are well investigated, there are no reports on the volatiles from their corresponding hydrolates, which are the main by-products of EO isolation, as well as on their biological activity. Therefore, the composition and biological activities of EOs and corresponding hydrolates of sea fennel from Atlantic (French, FRA) and Mediterranean (Croatian, CRO) ecotypes were investigated and compared. The EO from the CRO sample was characterized by an abundance of sabinene and limonene, while that from the FRA ecotype was rich in dillapiol and carvacryl methyl ether. The CRO hydrolate was rich in terpinen-4-ol and 10-(acetylmethyl)-3-carene, while dillapiol, thymyl methyl ether and γ-terpinene were the main compounds in the FRA sea fennel hydrolate. The biological activities of the EOs and hydrolates were evaluated for their antioxidant (with DPPH, NO, FRAP and ORAC bioassays), antimicrobial (against some Gram+ and Gram- spoilage bacteria) and antiageing (tyrosinase, elastase and collagenase inhibition) activities. Both EOs showed low reducing powers and antiradical activities while the ability of both hydrolates to quench NO was slightly higher (35-39% if inhibition). The FRA EO showed low activity against Staphylococcus aureus (8 mm), while CRO moderately inhibited the growth of P. aeruginosa (8 mm), but strongly inhibited the other two bacterial strains. While the French EO showed no antityrosinase and anticollagenase activity, the Croatian oil significantly inhibited both enzymes (IC50 of 650 µg/mL and IC50 of 2570 µg/mL, respectively) probably due to the dominance of limonene and sabinene. Neither EO exhibited antielastase properties, while the hydrolates from both ecotypes showed no antiageing activity, regardless of the enzyme tested. The EOs from the aerial parts of sea fennel from FRA and CRO differed greatly in composition, resulting in different activities. The Croatian samples appeared to have better biological properties and are therefore good candidates for applications as preservatives or antiageing agents.

Valorisation of prawn/shrimp shell waste through the production of biologically active components for functional food purposes

BACKGROUND

The aim of the work was to develop a technology for using waste from prawn and shrimp processing as a source of active ingredients that could be used in the promotion of healthy foods. From fresh and freeze-dried prawn and shrimp shells, protein hydrolysates (carotenoproteins) were obtained using two different enzymes, Flavourzyme and Protamex.

RESULTS

The obtained hydrolysates were characterised in terms of protein content, degree of hydrolysis, and antioxidant and antimicrobial activity. The hydrolysate with the best antioxidant properties (FRAP value of 2933.33 μmol L-1 TE; ORAC value of 115.58 μmol L-1 TE) was selected and tested for its possible use as a component of functional foods. Molecular weight distribution, amino acid profile and free amino acids, the solubility of the hydrolysate in different pH ranges as well as foaming ability were determined. It was found that this hydrolysate was characterised by an amino acid profile with high nutritional value, flavour enhancement properties and excellent solubility in a wide pH range (from 97.06% to 100%). Afterward, the possibility of using carotenoproteins from prawn waste as a component of an emulsion with furcellaran and a lipid preparation of astaxanthin, taken from post-hydrolysate production waste, was investigated. The obtained complexes were stable as proved by the measurement of zeta potential (ζ = -23.87 and -22.32 to -27.79 mV).

CONCLUSION

It is possible to produce stable complexes of the hydrolysate with furcellaran and to emulsify a lipid preparation of astaxanthin, obtained from waste following production of the hydrolysate, in them. © 2023 Society of Chemical Industry.

Evaluation of the Impact of Alternanthera philoxeroides (Mart.) Griseb. Extract on Memory Impairment in D-Galactose-Induced Brain Aging in Mice through Its Effects on Antioxidant Enzymes, Neuroinflammation, and Telomere Shortening

Aging is a well-known factor that accelerates brain deterioration, resulting in impaired learning and memory functions. This current study evaluated the potential of an extract of Alternanthera philoxeroides (AP), an edible flavonoid-rich plant, to ameliorate D-galactose-induced brain aging in male mice. Chronic administration of D-galactose (150 mg/kg/day) in mice mimicked the characteristics of aging by accelerating senescence via downregulation of the following telomere-regulating factors: mouse telomerase reverse transcriptase (mTERT) and mouse telomeric repeat-binding factors 1 (mTRF1) and 2 (mTRF2). D-galactose also decreased the activities of the antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD), while increasing expression of neuroinflammatory cytokines in the frontal cortex and hippocampus. Daily treatment of D-galactose-induced aging mice with AP at 250 and 500 mg/kg/day or vitamin E (100 mg/kg/day) significantly increased the activities of SOD and CAT, as well as expression of mTERT, mTRF1, and mTRF2, which are involved in telomere stabilization, but decreased the levels of proinflammatory cytokines IL-1β, IL-6, and TNF-α. In the behavioral portion of the study, AP improved aging-related cognitive deficits in short-term memory as shown by the Y-maze task and the novel object recognition test (NORT) and long-term memory as shown by the Morris water maze test (MWMT). The flavones kaempferol-O-glucoside (1), quercetin (2), alternanthin B (3), demethyltorosaflavone D (4), and chrysoeriol-7-O-rhamnoside (5), which could be responsible for the observed effects of AP in the D-galactose-induced aging mice, were identified by HPLC analysis.

Seasonal Monitoring of Volatiles and Antioxidant Activity of Brown Alga Cladostephus spongiosus

Cladostephus spongiosus was harvested once a month during its growing season (from May to August) from the Adriatic Sea. Algal volatile organic compounds (VOCs) were obtained by headspace solid-phase microextraction (HS-SPME) and hydrodistillation (HD) and analysed by gas chromatography and mass spectrometry (GC-MS). The effects of air drying and growing season on VOCs were determined. Two different extraction methods (ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE)) were used to obtain ethanolic extracts of C. spongiosus. In addition, the seasonal antioxidant potential of the extracts was determined, and non-volatile compounds were identified from the most potent antioxidant extract. Aliphatic compounds (e.g., pentadecane) were predominantly found by HS-SPME/GC-MS. Hydrocarbons were more than twice as abundant in the dry samples (except in May). Aliphatic alcohols (e.g., hexan-1-ol, octan-1-ol, and oct-1-en-3-ol) were present in high percentages and were more abundant in the fresh samples. Hexanal, heptanal, nonanal, and tridecanal were also found. Aliphatic ketones (octan-3-one, 6-methylhept-5-en-2-one, and (E,Z)-octa-3,5-dien-2-one) were more abundant in the fresh samples. Benzene derivatives (e.g., benzyl alcohol and benzaldehyde) were dominant in the fresh samples from May and August. (E)-Verbenol and p-cymen-8-ol were the most abundant in dry samples in May. HD revealed aliphatic compounds (e.g., heptadecane, pentadecanal, (E)-heptadec-8-ene, (Z)-heptadec-3-ene), sesquiterpenes (germacrene D, epi-bicyclosesquiphellandrene, gleenol), diterpenes (phytol, pachydictyol A, (E)-geranyl geraniol, cembra-4,7,11,15-tetraen-3-ol), and others. Among them, terpenes were the most abundant (except for July). Seasonal variations in the antioxidant activity of the ethanolic extracts were evaluated via different assays. MAE extracts showed higher peroxyl radical inhibition activity from 55.1 to 74.2 µM TE (Trolox equivalents). The highest reducing activity (293.8 µM TE) was observed for the May sample. Therefore, the May MAE extract was analysed via high-performance liquid chromatography with high-resolution mass spectrometry and electrospray ionisation (UHPLC-ESI-HRMS). In total, 17 fatty acid derivatives, 9 pigments and derivatives, and 2 steroid derivatives were found. The highest content of pheophorbide a and fucoxanthin, as well as the presence of other pigment derivatives, could be related to the observed antioxidant activity.

Photoprotective and Anti-Aging Properties of the Apical Frond Extracts from the Mediterranean Seaweed Ericaria amentacea

There is a growing interest in using brown algal extracts thanks to the bioactive substances they produce for adaptation to the marine benthic environment. We evaluated the anti-aging and photoprotective properties of two types of extracts (50%-ethanol and DMSO) obtained from different portions, i.e., apices and thalli, of the brown seaweed, Ericaria amentacea. The apices of this alga, which grow and develop reproductive structures during summer when solar radiation is at its peak, were postulated to be rich in antioxidant compounds. We determined the chemical composition and pharmacological effects of their extracts and compared them to the thallus-derived extracts. All the extracts contained polyphenols, flavonoids and antioxidants and showed significant biological activities. The hydroalcoholic apices extracts demonstrated the highest pharmacological potential, likely due to the higher content of meroditerpene molecular species. They blocked toxicity in UV-exposed HaCaT keratinocytes and L929 fibroblasts and abated the oxidative stress and the production of pro-inflammatory cytokines, typically released after sunburns. Furthermore, the extracts showed anti-tyrosinase and anti-hydrolytic skin enzyme activity, counteracting the collagenase and hyaluronidase degrading activities and possibly slowing down the formation of uneven pigmentation and wrinkles in aging skin. In conclusion, the E. amentacea apices derivatives constitute ideal components for counteracting sunburn symptoms and for cosmetic anti-aging lotions.

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.

Golden Chanterelle or a Gold Mine? Metabolites from Aqueous Extracts of Golden Chanterelle (Cantharellus cibarius) and Their Antioxidant and Cytotoxic Activities

Cantharellus cibarius, the golden chanterelle, is the second most-collected wild edible mushroom in Europe and very frequently harvested in Croatia. Wild mushrooms have been considered a healthy food since ancient times and are today highly valued for their beneficial nutritional as well as medicinal properties. Since golden chanterelle is added to different food products to improve their nutritive value, we studied the chemical profile of aqueous extracts of golden chanterelle (at 25 °C and 70 °C) and their antioxidant and cytotoxic activities. Malic acid, pyrogallol and oleic acid were some of the main compounds identified by GC-MS from derivatized extract. p-Hydroxybenzoic acid, protocatechuic acid and gallic acid were the most abundant phenolics quantitatively determined by HPLC, with somewhat higher amounts for samples extracted at 70 °C. Antioxidant activity was determined by ferric reducing antioxidant power assay and oxygen radical absorption method, and the highest results were recorded for golden chanterelle extracted at 70 °C, being 41.54 ± 1.54 and 38.72 ± 2.47 µM TE/L, respectively. Aqueous extract at 25 °C showed the better response against human breast adenocarcinoma MDA-MB-231 (IC₅₀ = 375µg/mL). Our results confirm the beneficial effect of golden chanterelle even under aqueous extraction conditions and highlight its significance as a dietary supplement and in the development of new beverage products.

Stabilization Activity of Kelp Extract in Ethylene-Propylene Rubber as Safe Packaging Material

This paper presents the stabilization effects of the solid extract of kelp (Ascophyllum nodosum) on an engineering elastomer, ethylene-propylene copolymer (EPR), which may be used as packaging material. Progressive increase in additive loadings (0.5, 1, and 2 phr) increases the oxidation induction time for thermally aged rubber at 190 °C from 10 min to 30 min for pristine material and modified polymer by adding 2 phr protection powder. When the studied polymer is γ-irradiated at 50 and 100 kGy, the onset oxidation temperatures increase as a result of blocking the oxidation reactivity of free radicals. The stabilization effect occurs through the activity of alginic acid, which is one of the main active components associated with alginates. The accelerated degradation caused by γ-exposure advances more slowly when the kelp extract is present. The OOT value for the oxidation of EPR samples increases from 130 °C to 165 °C after the γ-irradiation of pristine and modified (2 phr of kelp powder) EPR, respectively. The altered oxidation state of EPR samples by the action of γ-rays in saline serum is faster in neat polymer than in stabilized material. When the probes are placed in physiological serum and irradiated at 25 kGy, the OOT value for neat EPR (145 °C) is much lower than the homologous value for the polymer samples protected by kelp extract (153 °C for the concentration of 0.5 phr, 166 °C for the concentration of 1 phr, and 185 °C for the concentration of 2 phr).

Phytochemical Investigation of Three Cystoseira Species and Their Larvicidal Activity Supported with In Silico Studies

Culex pipiens mosquitoes are transmitters of many viruses and are associated with the transmission of many diseases, such as filariasis and avian malaria, that have a high rate of mortality. The current study draws attention to the larvicidal efficacy of three methanolic algal extracts, Cystoseira myrica, C. trinodis, and C. tamariscifolia, against the third larval instar of Cx. pipiens. The UPLC-ESI-MS analysis of three methanol fractions of algal samples led to the tentative characterization of twelve compounds with different percentages among the three samples belonging to phenolics and terpenoids. Probit analysis was used to calculate the lethal concentrations (LC₅₀ and LC₉₀). The highest level of toxicity was attained after treatment with C. myrica extract using a lethal concentration 50 (LC₅₀) of 105.06 ppm, followed by C. trinodis (135.08 ppm), and the lowest level of toxicity was achieved by C. tamariscifolia (138.71 ppm) after 24 h. The elevation of glutathione-S-transferase (GST) and reduction of acetylcholine esterase (AChE) enzymes confirm the larvicidal activity of the three algal extracts. When compared to untreated larvae, all evaluated extracts revealed a significant reduction in protein, lipid, and carbohydrate contents, verifying their larvicidal effectiveness. To further support the observed activity, an in silico study for the identified compounds was carried out on the two tested enzymes. Results showed that the identified compounds and the tested enzymes had excellent binding affinities for each other. Overall, the current work suggests that the three algal extractions are a prospective source for the development of innovative, environmentally friendly larvicides.

In the Beginning Was the Bud: Phytochemicals from Olive (Olea europaea L.) Vegetative Buds and Their Biological Properties

Even though Olea europaea L. is one of the most important and well-studied crops in the world, embryonic parts of the plants remain largely understudied. In this study, comprehensive phytochemical profiling of olive vegetative buds of two Croatian cultivars, Lastovka and Oblica, was performed with an analysis of essential oils and methanol extracts as well as biological activities (antioxidant, antimicrobial, and cytotoxic activities). A total of 113 different volatiles were identified in essential oils with hydrocarbons accounting for up to 60.30% and (Z)-3-heptadecene being the most abundant compound. Oleacein, oleuropein, and 3-hydroxytyrosol had the highest concentrations of all phenolics in the bud extracts. Other major compounds belong to the chemical classes of sugars, fatty acids, and triterpenoid acids. Antioxidant, antimicrobial, and cytotoxic activities were determined for both cultivars. Apart from antioxidant activity, essential oils had a weak overall biological effect. The extract from cultivar Lastovka showed much better antioxidant activity than both isolates with both methods (with an oxygen radical absorbance capacity value of 1835.42 μM TE/g and DPPH IC₅₀ of 0.274 mg/mL), as well as antimicrobial activity with the best results against Listeria monocytogenes. The human breast adenocarcinoma MDA-MB-231 cell line showed the best response for cultivar Lastovka bud extract (IC₅₀ = 150 μg/mL) among three human cancer cell lines tested. These results demonstrate great chemical and biological potential that is hidden in olive buds and the need to increase research in the area of embryonic parts of plants.

Bio-Guided Optimization of Cystoseira abies-marina Cosmeceuticals Extraction by Advanced Technologies

Cystoseira abies-marina (reclassified as Gongolaria abies-marina) is a brown seaweed species rich in meroterpenoids, presenting interesting antioxidant, antitumor, and anti-inflammatory activities. However, there is still a lot to uncover regarding the bioactive potential of this species, as evidenced by the lack of records of antiaging activities from Cystoseira abies-marina, making this macroalga an excellent candidate for studies of its cosmeceutical potential. Ultrasound-(UAE) and microwave-assisted extraction (MAE) are advanced sustainable technologies that are very efficient in enhancing bioactive compound extraction. Applying these extraction techniques to a new biological matrix often calls for optimizing the parameters toward the best extraction yield. Since Cystoseira abies-marina is a new matrix for both UAE and MAE techniques, the present work proposes the optimization of the extraction process, using a novel approach: instead of only focusing on increasing the yield, the goal of this work is to determine the parameters for UAE and MAE that lead to extracts with better antiaging activities. For this bio-guided approach, several Cystoseira abies-marina extracts were prepared by UAE and MAE under varying conditions of solvent, time, and algae/solvent ratios. Their antiaging activities were then determined, and all the results combined to unveil the conditions yielding extracts with higher cosmeceutical potential. Using statistical tools, it was found that, for UAE, the best conditions were ethyl acetate, 15 min, and a ratio of 1:4, which led to an extract with high yield, and causing the strong inhibition of tyrosinase and elastase. In turn, ethanol, 10 min, and a ratio of 1:4 were the best conditions for MAE, leading to the extract with the best antioxidant activity. The results show that the proposed bio-guided approach was effective in obtaining extracts with high cosmeceutical potential, unveiling the possibility of modulating an extract's activity by changing the extraction method.

Seaweed as a Natural Source against Phytopathogenic Bacteria

Plant bacterial pathogens can be devastating and compromise entire crops of fruit and vegetables worldwide. The consequences of bacterial plant infections represent not only relevant economical losses, but also the reduction of food availability. Synthetic bactericides have been the most used tool to control bacterial diseases, representing an expensive investment for the producers, since cyclic applications are usually necessary, and are a potential threat to the environment. The development of greener methodologies is of paramount importance, and some options are already available in the market, usually related to genetic manipulation or plant community modulation, as in the case of biocontrol. Seaweeds are one of the richest sources of bioactive compounds, already being used in different industries such as cosmetics, food, medicine, pharmaceutical investigation, and agriculture, among others. They also arise as an eco-friendly alternative to synthetic bactericides. Several studies have already demonstrated their inhibitory activity over relevant bacterial phytopathogens, some of these compounds are known for their eliciting ability to trigger priming defense mechanisms. The present work aims to gather the available information regarding seaweed extracts/compounds with antibacterial activity and eliciting potential to control bacterial phytopathogens, highlighting the extracts from brown algae with protective properties against microbial attack.

Brown Macroalgae (Phaeophyceae): A Valuable Reservoir of Antimicrobial Compounds on Northern Coast of Spain

The search for new sources of antimicrobial compounds has become an urgent need, due to the threat that the spread of bacterial resistance represents for global health and food safety. Brown macroalgae have been proposed as a great reservoir in the search for novel antimicrobial compounds. In this study, mid-polarity extracts were performed with a selection of 20 brown macroalgae species from northern Spain. The total polyphenol, carbohydrate and protein contents were quantified by spectrophotometry. The volatile organic compounds (VOCs) of whole macroalgae were also studied as a biomarker of their metabolic state in the representative species of the tested families by gas chromatography-mass spectrometry (GC-MS). The antimicrobial potential of the extracts was assessed by a disk diffusion assay against 20 target bacteria and further determinations of the minimum inhibitory (MIC) and minimum bactericidal concentrations (MBC) were performed by a microdilution assay for the active extracts. Ericaria selaginoides, Bifurcaria bifurcata and Dictyota dichotoma showed an antimicrobial effect against six Gram-positive strains: Bacillus cereus, Bacillus subtilis, Geobacillus stearothermophilus, Listeria monocytogenes, Staphylococcus aureus and Staphylococcus haemolyticus. The phenolic content was generally higher in the extracts that showed antimicrobial activity, followed by carbohydrates and low contents of proteins. The results obtained in this study reveal the potential of brown macroalgae as a promising alternative source of antimicrobial compounds as functional ingredients for the application in industrial fields.

Seasonal Changes in Chemical Profile and Antioxidant Activity of Padina pavonica Extracts and Their Application in the Development of Bioactive Chitosan/PLA Bilayer Film

Seaweeds are a potentially sustainable source of natural antioxidants that can be used in the food industry and possibly for the development of new sustainable packaging materials with the ability to extend the shelf-life of foods and reduce oxidation. With this in mind, the seasonal variations in the chemical composition and antioxidant activity of brown seaweed (Padina pavonica) extracts were investigated. The highest total phenolic content (TPC) and antioxidant activity (measured by ferric reducing/antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, and oxygen radical absorbance capacity (ORAC)) were found for P. pavonica June extract. The TPC of 26.69 ± 1.86 mg gallic acid equivalent/g, FRAP of 352.82 ± 15.41 µmole Trolox equivalent (TE)/L, DPPH of 52.51 ± 2.81% inhibition, and ORAC of 76.45 ± 1.47 µmole TE/L were detected. Therefore, this extract was chosen for the development of bioactive PLA bilayer film, along with chitosan. Primary or quaternary chitosan was used as the first layer on polylactic acid (PLA) films. A suspension of chitosan particles with entrapped P. pavonica extract was used as the second layer. X-ray photoelectron spectroscopy confirmed the presence of layers on the material surface. The highest recorded antioxidant activity of the newly developed films was 63.82% inhibition. The developed functional films exhibited antifogging and antioxidant properties, showing the potential for application in the food industry.

Comparison of Growth and Chemical Profile of Diatom Skeletonema grevillei in Bioreactor and Incubation-Shaking Cabinet in Two Growth Phases

Marine microalgae, diatoms, are considered a source of a wide range of high-value compounds, and numerous studies indicate their biotechnological potential in the food and feed industry, cosmetic industry, nanotechnology, pharmaceutical industry, biodiesel production, fertilizers, and wastewater treatment. The aim of this study was to compare the growth, chemical profiles, and antioxidant activity of the diatom Skeletonema grevillei cultivated in a bioreactor and an incubation-shaking cabinet at different growth phases (after 192 and 312 h). Growth was monitored by evaluating cell density with the Sedgewick Rafter chamber, and the collected biomass was extracted with 70% ethanol assisted by ultrasound. Extracts were evaporated to dryness and compounds were identified in derivatized form by gas chromatography and mass spectrometry (GC-MS) analysis, while antioxidant capacity was evaluated by DPPH and ORAC. Significantly faster growth was observed in the bioreactor than in the incubation-shaking cabinet. Oleamide, palmitelaidic acid, glycerol monostearate, myristic acid, cholesterol, eicosapentaenoic acid, 1-monopalmitin, and 24-methylene cholesterol were identified as the major compounds in both systems. Among them, oleamide was the dominant compound in both systems. It is also shown that prolonging the cultivation period had a direct effect on increasing the extract yield. The highest DPPH inhibition (11.4 ± 1%) and ORAC values (93.3 ± 8.4 mM TE) were obtained for the S. grevillei extract recovered from the bioreactor after 312 h. The obtained results contribute to the possibility of using S. grevillei for various biotechnological applications in the future.

Limited Stress Response to Transplantation in the Mediterranean Macroalga Ericaria amentacea, a Key Species for Marine Forest Restoration

In the Mediterranean Sea, brown macroalgae represent the dominant species in intertidal and subtidal habitats. Despite conservation efforts, these canopy-forming species showed a dramatic decline, highlighting the urge for active intervention to regenerate self-sustaining populations. For this reason, the restoration of macroalgae forests through transplantation has been recognized as a promising approach. However, the potential stress caused by the handling of thalli has never been assessed. Here, we used a manipulative approach to assess the transplant-induced stress in the Mediterranean Ericaria amentacea, through the analysis of biochemical proxies, i.e., phenolic compounds, lipids, and fatty acids in both transplanted and natural macroalgae over time. The results showed that seasonal environmental variability had an important effect on the biochemical composition of macroalgae, suggesting the occurrence of acclimation responses to summer increased temperature and light irradiance. Transplant-induced stress appears to have only amplified the biochemical response, probably due to increased sensitivity of the macroalgae already subjected to mechanical and osmotic stress (e.g., handling, wounding, desiccation). The ability of E. amentacea to cope with both environmental and transplant-induced stress highlights the high plasticity of the species studied, as well as the suitability of transplantation of adult thalli to restore E. amentacea beds.

Investigation of Antioxidant Synergisms and Antagonisms among Phenolic Acids in the Model Matrices Using FRAP and ORAC Methods

The total antioxidant potential of a sample cannot be predicted from the antioxidant activity of its compounds; thus, scientists usually explain the overall activity through their combined effects (synergistic, antagonistic, or additive). Phenolic compounds are one of the most powerful and widely investigated antioxidants, but there is a lack of information about their molecular interactions. This study aimed to investigate the individual and combined antioxidant activity of equimolar mixtures (binary, ternary, quaternary, and quinary) of 10 phenolic acids (protocatechuic, gentisic, gallic, vanillic, syringic, p-coumaric, caffeic, ferulic, sinapic, and rosmarinic acid) at different concentrations using ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC) assays. Gallic acid showed the highest antioxidant activity, determined using the FRAP assay (494-5033 µM Fe2+) and rosmarinic acid with the ORAC assay (50-92 µM Trolox Equivalents (TE)), while the lowest antioxidant potential was observed for p-coumaric acid (FRAP 24-113 µM Fe2+ and ORAC 20-33 µM TE). The synergistic effect (by FRAP) in the equimolar mixtures of hydroxybenzoic acids was confirmed for a large number of tested mixtures, especially at low concentrations. All mixtures containing gentisic acid showed a synergistic effect (28-89% difference). Using the ORAC method, only two mixtures of hydroxybenzoic acids showed an antagonistic effect, namely a mixture of gentisic + syringic acids (-24% difference) and gallic + vanillic acids (-30% difference), while all other mixtures showed a synergistic effect in a range of 26-236% difference. Among mixtures of hydroxycinnamic acids, the highest synergistic effect was observed for the mixtures of p-coumaric + ferulic acids and caffeic + sinapic acids with differences of 311% and 211%, respectively. The overall antioxidant activity of phenolic acids could be explained by the number or position of hydroxyl and/or methoxy functional groups as well as the compound concentration, but the influence of other parameters such as dissociation, intramolecular hydrogen bonds, and electron donating or withdrawing effect should not be neglected.

Antioxidant and antimicrobial potential of six Fucoids from the Mediterranean Sea and the Atlantic Ocean

BACKGROUD

In recent years, research on the bioactive properties of macroalgae has increased, due to the great interest in exploring new products that can contribute to improve human health and wellbeing. In the present study, the antioxidant and antimicrobial potential of six different brown algae of the Fucales order were evaluated, namely Ericaria selaginoides, Ericaria amentacea, Gongolaria baccata, Gongolaria usneoides, Cystoseira compressa and Sargassum vulgare (collected along the Mediterranean and Atlantic coasts). The antioxidant capacity was measured by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, the oxygen radical absorbent capacity (ORAC) and the ferric reducing antioxidant power (FRAP) and were related to the total phenolic content (TPC). The antimicrobial activity was evaluated measuring the growth inhibition of Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans.

RESULTS

The highest antioxidant capacity was obtained for Ericaria selaginoides revealing the highest capacity to scavenge DPPH radical [half maximal effective concentration (EC50 ) = 27.02 μg mL-1 ], highest FRAP (1761.19 μmol FeSO4 equivalents g-1 extract), high ORAC (138.92 μmol TE g-1 extract), alongside to its high TPC (121.5 GAE g-1 extract). This species also reported the highest antimicrobial capacity against Staphylococcus aureus [half maximal inhibitory concentration (IC50 ) = 268 μg mL-1 ].

CONCLUSIONS

Among all studied seaweed, Ericaria selaginoides reveals the highest antioxidant and antimicrobial activities, and thus should be explored as a natural food additive and/or functional ingredient. © 2022 Society of Chemical Industry.

Antioxidant and Antimicrobial Activity of Hydroethanolic Leaf Extracts from Six Mediterranean Olive Cultivars

Phenolic profiles, antioxidant, and antimicrobial activities of hydroethanolic olive leaf extracts from six Mediterranean olive cultivars (Croatian: Lastovka, Levantinka, Oblica; Italian: Moraiolo, Frantoio, Nostrana di Brisighella) were investigated. As expected, various distributions of phenolic levels were observed for each cultivar and the total phenolic content showed high variability (ranging from 4 to 22 mg GAE/g of dry extract), with the highest amount of phenolics found in the Oblica sample, which also provided the highest antiradical (ORAC) and reducing activity (FRAP). The screening of individual compounds was performed by HPLC-PDA-ESI-QTOF-MS and the main detected compounds were oleuropein, hydroxytyrosol, oleoside/secologanoside, verbascoside, rutin, luteolin glucoside, hydroxyoleuropein, and ligstroside. While the antioxidant activity of the samples was relatively high, they showed no bactericidal and bacteriostatic activity against E. coli and S. Typhimurium; weak activity against Staphylococcus aureus, Bacillus cereus, and Listeria innocua; and inhibitory effects against Campylobacter jejuni at 0.5 mg dry extract/mL. The obtained results support the fact that olive leaf extracts, and especially those from the Oblica cultivar, could potentially be applied in various industries as natural preservatives and effective and inexpensive sources of valuable antioxidants.

Determination of Antioxidant, Antimicrobial Activity, Heavy Metals and Elements Content of Seaweed Extracts

The aim of the research was to determine the antioxidant and antimicrobial activity, determination of chemical elements and heavy metals in seaweed extracts of wakame, arame, dulse, laminaria, kombu, and hijiki. Antioxidant activity was determined by DPPH method and the activity ranged from 0.00 to 2641.34 TEAC. The highest antioxidant activity was observed in kombu (2641.34 TEAC) and arame (2457.5 TEAC). Antimicrobial activity was analyzed by disk diffusion method and MIC method. Three G+ bacteria (Staphylococcus aureus, Enterococcus faecalis, Bacillus subtilis), three G- bacteria (Salmonella enterica, Pseudomonas aeruginosa, Yersinia enterocolitica), and four yeasts (Candida tropicalis, C. krusei, C. glabrata, C. albicans) were used as model organisms. The size of inhibition zones ranged from 0.00 to 8.67 mm. The minimum inhibitory concentrations of the selected seaweeds ranged from MIC50 98.46 (MIC90 100.25) to MIC50 3.43 µL/mL (MIC90 5.26 µL/mL). The content of selected elements was determined in seaweed samples by ICP-OES. The chemical composition of the algae showed differences between species and the presence of heavy metals. Arsenic, cadmium, and aluminum were confirmed. All seaweed samples contained arsenic ranging from 6.6546 to 76.48 mg/kg. Further investigation of seaweeds is needed to identify the active substances present in the algae that are responsible for antioxidant and antimicrobial activity. This study was carried out to evaluate the antimicrobial and antioxidant activity of extracts from five commonly consumed seaweeds for their ability to inhibit selected microorganisms and to determine the health risk due to heavy metals content. Our study contributes to the evidence that seaweeds have antimicrobial and antioxidant activity and seaweed extracts have for pharmacological applications.

Carrageenan From Kappaphycus alvarezii (Rhodophyta, Solieriaceae): Metabolism, Structure, Production, and Application

Carrageenan is a polysaccharide derived from red algae (seaweed) with enormous economic potential in a wide range of industries, including pharmaceuticals, food, cosmetics, printing, and textiles. Carrageenan is primarily produced through aquaculture-based seaweed farming, with Eucheuma and Kappaphycus species accounting for more than 90% of global output. There are three major types of carrageenan found in red algae: kappa (κ)-, iota (ι)-, and lambda (λ)-carrageenan. Kappaphycus alvarezii is the most common kappa-carrageenan source, and it is primarily farmed in Asian countries such as Indonesia, the Philippines, Vietnam, and Malaysia. Carrageenan extracted from K. alvarezii has recently received a lot of attention due to its economic potential in a wide range of applications. This review will discuss K. alvarezii carrageenan in terms of metabolic and physicochemical structure, extraction methods and factors affecting production yield, as well as current and future applications.

Bio-Based Products from Mediterranean Seaweeds: Italian Opportunities and Challenges for a Sustainable Blue Economy

Seaweeds are attracting increasing attention as an alternative healthy food and renewable drugs source and as agents of climate change mitigation that provide essential ecosystem services. In this context, seaweeds represent marine resources capable of supporting and pursuing the objectives of the Sustainable Blue Economy and the Bio-Based Circular Economy. In this review, we analyze the state of seaweed bio-based products and research on the Mediterranean Sea from the last 20 years. Results of this analysis show a large number of investigations focusing on antimicrobial, antioxidant and anti-inflammatory activities compared to on biofuels and bioplastics. Attempts at seaweed farming, although generally very limited, are present in Israel and some North African countries. Lastly, we focus on the Italian situation—including research, companies and legislation on seaweed production—and we discuss gaps, perspectives and challenges for the potential development of a sustainable seaweed industry according to the Sustainable Blue Economy.