Mycosporine-like Amino Acids Concentrations Research Articles

UV-absorbing mycosporine-like amino acids in the eyes of temperate marine and freshwater fish species

Ultraviolet radiation (UVR) is the photochemically most reactive waveband of incident solar irradiation. Despite high absorption in aquatic environments, UVR causes numerous biochemical, genetic, and cytotoxic effects in aquatic organisms. To counteract UVR stress, many of those species are able to synthesize, accumulate, or acquire UV-sunscreen compounds for photoprotection from their diet. The most abundant UV sunscreens in marine and freshwater organisms are mycosporine-like amino acids (MAAs), which exhibit high molar extinction coefficients in the UVR range along with a strong photo- and heat stability. In this study, we investigated the qualitative and quantitative MAA distribution patterns in the eyes of 39 fish species, mainly from the temperate northern hemisphere (Baltic Sea, Northern Atlantic), using state-of-the-art analytical methods. The fish eyes of the most investigated species (33 taxa) contained MAAs, between one and seven different compounds. The MAAs palythine, asterina-330, palythene, and usujirene were present (as previously reported), and three new compounds, aplysiapalythine A, porphyra-334, and shinorine, were identified. Total MAA concentrations covered a wide range from trace amounts to > 4.2 mg g−1 dry weight, thereby providing the first quantitative data on MAAs in fish eyes. The highest MAA contents were measured in Sprattus sprattus, which are comparable to those of intertidal red seaweeds. The trophic transfer of MAAs from primary producers via zooplankton to the fish is discussed, along with the localization in the fish eye as well as possible additional functions.

Daily variations on photosynthesis, pigmentation and photoprotection of Plocamium cartilagineum (Plocamiaceae, Rhodophyta)

ABSTRACT Field studies are a useful tool to understanding how seaweeds develop protective mechanisms against environmental variation and acclimate to them. These mechanisms can include morphological changes, inhibition of electron transportation rate, pigments and UV-absorbing compounds production. The present paper evaluates the daily cycle of photosynthesis and biochemistry of Plocamium cartilagineum from Spain under varying radiation and temperature conditions. For this purpose, four sites were chosen at La Herradura beach, Spain. Photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) were measured in situ at the sites, and ETR in situ (electron transport rate) as an estimator of photosynthetic capacity was determined. Algal thalli from each site were sampled throughout the day at 09:30, 11:00, 13:00, 15:30, 17:00, 19:30 h, to quantify photosynthetic pigments, UV-photoprotective compounds (i.e. mycosporine-like amino acids, MAAs), and antioxidant capacity. Higher irradiance and temperature at two sites directly influenced ETR in situ . Algae from the site with highest PAR and UV radiation had dynamic photoinhibition when compared to algae from a more shaded site during certain periods of the day. Lower pigment concentrations were observed in algae that received higher irradiances, suggesting photoacclimation. Samples found at the site exposed to the highest ultraviolet-A radiation had the highest concentrations of mycosporine-like amino acids between 15:30 h and 19:30 h. MAAs proportion varied among the sites and during the day. We conclude that environmental conditions in the short-term influenced photosynthetic parameters and the accumulation of pigments and MAAs in P. cartilagineum showing its high physiological plasticity.

Enhancing Mycosporine-Like Amino Acids (MAAs) Extraction Yield from Fischerella sp. F5 using Experimental Design

Background: Mycosporine-like amino acids (MAAs) are ultraviolet-absorbing metabolites found in cyanobacteria, fungi, algae, and animals, known for their antioxidant and anti-inflammatory properties. Objectives: This study aimed to optimize MAAs extraction from Fischerella sp. F5 using experimental design techniques. Methods: The central composite design was employed to determine the optimal levels of five factors: Total extraction time, temperature, sonication time, methanol ratio, and solvent volume. Each run involved extracting 100 mg of dried biomass under the specified conditions. Mycosporine-like amino acids content was quantified using high performance liquid chromatography (HPLC), and the antioxidant activity of the extract was assessed using the DPPH radical scavenging test. The best model was selected based on the highest R2 value, and the optimized extraction conditions were determined. Results: Mycosporine-like amino acids content in the final extracts ranged from 27.7% to 89%, with antioxidant activities ranging from 15% to 59.3%. Overall, all factors showed a positive correlation with MAAs content in the final extract. However, no significant model was established to correlate extraction conditions with MAAs purity ratio (MAA%) or extract antioxidant activity. Conclusions: The bioactivity of partially purified MAAs may be influenced by factors such as associated impurities extracted alongside MAAs, which were not investigated in this study. Further research is necessary to identify the exact factors affecting MAAs extraction yield and purity, aiming to obtain partially purified MAAs extracts with optimal bioactivity.

Extraction and antioxidant capacity of mycosporine-like amino acids from red algae in Japan.

Mycosporine-like amino acids (MAAs) are the natural UV-absorbing compounds with antioxidant activity found in microalgae and macroalgae. We collected red algae Asparagopsis taxiformis, Meristotheca japonica, and Polysiphonia senticulosa from Nagasaki, where UV radiation is more intense than in Hokkaido, and investigated the effect of UV radiation on MAA content. It was suggested that A. taxiformis and M. japonica contained shinorine and palythine, while UV-absorbing compound in P. senticulosa could not be identified. The amounts of these MAAs were lower compared to those from Hokkaido. Despite an increase in UV radiation in both regions from February to April, MAA contents of red algae from Nagasaki slightly decreased while those from Hokkaido significantly decreased. This difference was suggested the amount of inorganic nitrogen in the ocean. Antioxidant activity of MAAs increased under alkaline conditions. The extract containing MAAs from P. senticulosa showed the highest antioxidant activity among 4 red algae.

Characterization of Mycosporine-like Amino Acids in Chlorophyll f Producing Cyanobacteria from Shaded Niches

Cyanobacteria are the oldest photoautotrophic prokaryotes that can perform plant-like oxygenic photosynthesis. The obligate requirement of sunlight for photosynthesis inevitably exposes cyanobacteria to UV radiation. Mycosporine-like amino acids (MAAs) played necessary roles in protecting cyanobacteria from UV radiation and were frequently reported in cyanobacteria exposed to high light radiation. Here, the MAA production was tried in the chlorophyll f-producing cyanobacterial strains isolated from the shaded environments. Four Chroococcidiopsis strains were finally induced to produce MAAs under 0.15 W·m-2 of UV-B exposure, and the MAA contents increased along with the prolonged UV-B treatments in these four Chroococcidiopsis strains. After separation by HPLC system, one MAA type was detected at similar retention times in the methanol extracts of Chroococcidiopsis strains, and all the MAA compounds showed in-line absorption at 310 nm and mass spectra 246 m/z. The absorption spectra and mass spectra matched well the characteristics of the simplest MAA mycosporine-glycine. Chroococcidiopsis had the simplest MAA gene clusters for mycosporine-glycine. MAAs could also be produced in the cyanobacteria even distributed in the light-deficient niches. These results suggested other roles of MAAs in addition to UV-B protection in the special cyanobacteria from shaded environments.

Characterization of Mycosporine-Like Amino Acids in Chlorophyll f Producing Cyanobacteria from Shaded Niches

Cyanobacteria are the oldest photoautotrophic prokaryotes that can perform plant-like oxygenic photosynthesis. The obligate requirement of sunlight for photosynthesis inevitably exposes cyanobacteria to UV radiation. Mycosporine-like amino acids (MAAs) played necessary roles in protecting cyanobacteria from UV radiation and were frequently reported in cyanobacteria exposed to high light radiation. Here, the MAA production was tried in the chlorophyll f-producing cyanobacterial strains isolated from the shaded environments. Four Chroococcidiopsis strains were finally induced to produce MAAs under 0.15 W·m-2 of UV-B exposure, and the MAA contents increased along with the prolonged UV-B treatments in these four Chroococcidiopsis strains. After separation by HPLC system, one MAA type was detected at the similar retention times in the methanol extracts of Chroococcidiopsis strains, and all the MAA compounds showed in-line absorption at 310 nm and mass spectra 246 m/z. The absorption spectra and mass spectra matched well the characteristics of the simplest MAA mycosporine-glycine. Chroococcidiopsis had the simplest MAA gene clusters for mycosporine-glycine. MAAs could also be produced in the cyanobacteria even distributed in the light-deficient niches. These results suggested other roles of MAAs in addition to UV-B protection in the special cyanobacteria from shaded environments.

Mycosporine-like Amino Acids in Palmaria palmata (Rhodophyta): Specific Implication of Usujirene in Photoprotection.

The effect of UV radiation on the accumulation of mycosporine-like amino acids (MAAs) and pigments was investigated on red macroalga Palmaria palmata cultivated for 21 days. The data were combined with the effect of NaNO3 to further investigate the synthesis of these nitrogenous compounds. A progressive decrease in both total MAA and pigment contents was observed, with a positive effect of nitrate supply. Usujirene was the only MAA exhibiting a significantly increasing content when exposed to UV radiation, changing from 9% to 24% of the total MAA's contribution, with no variation observed with NaNO3. This suggests a specific induction or synthesis pathway of usujirene for photoprotection, while the synthesis of other MAAs could have been limited by an insufficient amount of UV radiation and/or irradiance. The photoprotective ability of some MAAs could have been impacted by nitrogen starvation over time, resulting in a limited synthesis and/or potential use of MAAs as a nitrogen source for red macroalgae. The data confirmed the multiple effects of environmental factors on the synthesis of MAAs while providing new insights into the specific synthesis of usujirene, which could find an application in the cosmetics sector as natural sunscreen or an anti-ageing agent.

Argentine squid (Illex argentinus): A source of mycosporine-like amino acids with antioxidant properties

Here we report on the occurrence of mycosporine-like amino acids (MAAs) in the Argentine shortfin squid, Illex argentinus, the second fishery resource mostly exploited in the Argentinean continental shelf. The total content of four MAAs was evaluated by reverse-phase-HPLC in different tissues (eyes, skin, liver, and gonads). Also, the antioxidant activity of crude extracts was assessed by in-vitro determinations: 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), Folin-Ciocalteu, and ferrous ion-chelating capacity assays. The content of MAAs was found to be almost ten times higher in female gonads than in other tissues (11,89 ± 0,56 mg/g dry weight). Extracts from skin, female gonads and eyes, exhibit higher antioxidant activity than the reference compounds ascorbic acid and TROLOX. Overall, Argentine squid waste is a promising potential source of MAAs with antioxidant and UV photoprotective properties, which could bear interest in food, cosmetic and pharmaceutical industries, thus encouraging maximal and sustainable use of fishing resources.

Mycosporine-like Amino Acids from Red Alga Dulse (Devaleraea inkyuleei): Monthly Variation and Improvement in Extraction

Mycosporine-like amino acids (MAAs) are natural UV-absorbing compounds found in microalgae and macroalgae. The content of MAAs in algae varies with the seasons and environmental factors. Red alga dulse in Usujiri (Hokkaido, Japan) is an underutilized resource. Therefore, we investigated the amount of MAAs in Usujiri dulse in 2022 to clarify the suitable months for MAA extraction. In addition, we also evaluated the extraction method focusing on the extraction volume. MAAs were prepared via the 20 volumes of 25% ethanol extraction method and detected via HPLC. The results showed that the amount of MAAs on 25 March 2022 showed the highest value (40.4 μmol/g DW) among the samples from 24 January to 13 May. The tendency of suitable samples for MAA preparation corresponded to the term from mid-February to early April, which was the same as the previous three years. Although the surveys from 2019–2021 were performed by using the successive water–methanol method, it was found that the improved method also reflected the monthly variation in MAAs. The extraction of MAAs was performed via 20 or 40 volumes of 25% ethanol at 4 °C for 24 h. The amount of MAAs with 40 volumes of 25% ethanol extraction increased 1.3-fold compared to that with 20 volumes of 25% ethanol extraction. These data are useful information for valuable compound extraction from Usujiri dulse.

Improvement of the UV-resistance capability of fish gelatin-oxidized starch film via inserting mycosporine-like amino acids.

Mycosporine-like amino acids (MAAs) are known as the strongest solar guardians in nature. In the present study, the extraction of MAAs from dried Pyropia haitanensis was achieved. Fish gelatin and oxidized starch composite films embedded with MAAs (0-0.3% w/w) were fabricated. The maximum absorption wavelength of the composite film appeared at 334 nm, which was consistent with MAA solution. Furthermore, the UV absorption intensity of the composite film was highly dependent on the concentration of MAAs. The composite film exhibited excellent stability during the 7-day storage period. The physicochemical features of composite film were demonstrated by the measurement of water content, water vapor transmission rate, oil transmission, and visual characteristics. Furthermore, in the actual anti-UV effect investigation, the increase in peroxide value and the acid value of grease under the films coverage was delayed. In the meantime, the decrease in ascorbic acid content in dates was postponed, and survivability of Escherichia coli was increased. Our results suggest that fish gelatin-oxidized starch-mycosporine-like amino acids film (FOM film) with biodegradable and anti-ultraviolet properties has a high potential for usage in food packaging materials. © 2023 Society of Chemical Industry.

Rapid Screening for Mycosporine-like Amino Acids (MAAs) of Irish Marine Cyanobacteria and Their Antioxidant Potential

The present study evaluated 53 Irish marine cyanobacteria intending to identify potential producers of mycosporine-like amino acids (MAAs) to meet the increasing demand for replacing chemical sunscreen with bio-sunscreen. The biodiscovery analysis using absorption spectra of methanolic extracts identified eight cyanobacteria as potential MAAs producers with a specific content of 0.114–0.511 A* mg DW−1. Leptolyngbya tenuis SABC010201 was found to possess notably higher MAAs content. LC-MS analysis identified a total of eight different types of known MAAs (mycosporine-glutamicol, mycosporine-glutaminol-glucoside, mycosporine-serinol, mycosporine-taurine, palythine, palythine-threonine-sulphate, porphyra-334, and usujirene) in eight cyanobacteria, while four compounds were considered unknown UV-absorbing compounds with specific mass and absorption maximum. For example, two unknown compounds with, respectively, [M-H]- values of 219.0557 and 289.0730 and lambda max of 314 and 326 nm, were detected in three cyanobacteria Leptolyngbya tenuis SABC010201, Phormidium angustissimum SABC020801, and Schizothrix sp. SABC022401. These two unknown compounds were named M-314 and M-326, respectively. Antioxidant activities of total MAAs of all cyanobacteria showed considerable amounts of DPPH, FRAP, and ORAC activities. Considering the specific MAAs content and antioxidant activities, Leptolyngbya africana SABC021601 was considered the best producer of MAAs.

Monthly Variation in Mycosporine-like Amino Acids from Red Alga Dulse (Devaleraea inkyuleei, Formerly Palmaria palmata in Japan)

Mycosporine-like amino acids (MAAs) are natural ultraviolet-absorbing compounds found in microalgae and macroalgae. MAA content changes seasonally and in response to environmental factors. We previously investigated MAAs from the red alga dulse (Devaleraea inkyuleei, formerly Palmaria palmata in Japan) in Usujiri, Hokkaido, Japan, from 2019 to 2020. At that time, some factors affecting MAA content were still unclear. In this study, we investigated MAA variation during the period from January to June 2021, and evaluated new methods of MAA extraction from dulse. We recorded a maximum MAA extraction yield (7.03 µmol/g dry weight) on 25 March 2021. Over the course of our three years of investigations from 2019 to 2021, we found that dulse was most suitable for MAA preparation from the middle of February to late April. In the later work reported in this paper, we improved our extraction method by using a lower-risk organic solvent (ethanol) rather than methanol. In addition, we evaluated MAA extraction using different levels of ethanol concentration (25, 50, and 99%) and different extraction times (2, 6, and 24 h). We found that extraction with 25% ethanol for 24 h increased MAA content by a factor of 3.2, compared with our previous extraction method. In summary, we determined the most suitable sampling period for Usujiri dulse, to extract the highest content of MAAs. We also improved the effectiveness of the extraction process.

Separating and Purifying Mycosporine-like Amino Acids from Cyanobacteria for Application in Commercial Sunscreen Formulations.

Using algal-derived mycosporine-like amino acids (MAAs) in sunscreen formulations is constrained by low cellular concentrations of MAAs and by the high costs associated with harvesting algal cells and extracting the MAAs. Here, we report an industrial scalable method using a membrane filtration approach to purify and concentrate aqueous extracts of MAAs. The method includes an additional biorefinery step enabling purification of phycocyanin, an established valuable natural product. Cultivated cells of the cyanobacterium Chlorogloeopsis fritschii (PCC 6912) were concentrated and homogenised to produce a feed for sequential processing through three membranes of decreasing pore size to obtain a retentate and permeate for each step. Microfiltration (0.2 µm) was used to remove cell debris. Ultrafiltration (10,000 Da) was used to remove large molecules and recover phycocyanin. Finally, nanofiltration (300-400 Da) was used to remove water and other small molecules. Permeate and retentate were analysed using UV-visible spectrophotometry and HPLC. The initial homogenised feed had a shinorine concentration of 5.6 ± 07 mg L-1. The final nanofiltered retentate resulted in a 3.3 times-purified concentrate (shinorine concentration of 18.71 ± 0.29 mg L-1). Significant process losses (35%) highlight scope for improvement. Results confirm the potential of membrane filtration to purify and concentrate aqueous solutions of MAAs with simultaneous separation of phycocyanin highlighting a biorefinery approach.

Enhancing Bioproducts in Seaweeds via Sustainable Aquaculture: Antioxidant and Sun-Protection Compounds.

Marine macroalgae are considered an untapped source of healthy natural metabolites and their market demand is rapidly increasing. Intertidal macroalgae present chemical defense mechanisms that enable them to thrive under changing environmental conditions. These intracellular chemicals include compounds that can be used for human benefit. The aim of this study was to test cultivation protocols that direct seaweed metabolic responses to enhance the production of target antioxidant and photoprotective biomaterials. We present an original integrated multi-trophic aquaculture (IMTA) design, based on a two-phase cultivation plan, in which three seaweed species were initially fed by fish effluents, and subsequently exposed to various abiotic stresses, namely, high irradiance, nutrient starvation, and high salinity. The combined effect of the IMTA's high nutrient concentrations and/or followed by the abiotic stressors enhanced the seaweeds' content of mycosporine-like amino acids (MAAs) by 2.3-fold, phenolic compounds by 1.4-fold, and their antioxidant capacity by 1.8-fold. The Sun Protection Factor (SPF) rose by 2.7-fold, and the chlorophyll and phycobiliprotein synthesis was stimulated dramatically by an order of magnitude. Our integrated cultivation system design offers a sustainable approach, with the potential to be adopted by emerging industries for food and health applications.

Interactive effects of solar radiation and inorganic nutrients on biofiltration, biomass production, photosynthetic activity and the accumulation of bioactive compounds in Gracilaria cornea (Rhodophyta)

Interactive effects of solar radiation and inorganic nitrogen and phosphate on biofiltration capacity, biomass production, photosynthetic activity and the accumulation of bio-active compounds were studied in the red alga Gracilaria cornea grown in tanks with a seawater open-flow system during 35 days. Two light conditions were utilized: outdoor (O), full solar natural radiation, and indoor, inside of a greenhouse (G) where UV-B radiation was cut-off and part of the UV-A radiation was filtered. Two inorganic nitrogen and phosphate concentrations were used: High nutrients (HN; 100–200μM of NH4+ and 20μM of KHPO4) and Low nutrients (LN; 10–20μM of NH4+ and 1μM of KHPO4). Growth and biomass productivity were related to the daily integrated electron transport rate determined in situ, as an estimator of daily photosynthetic activity. Nitrogen uptake efficiency (NUE) was close to 100 % under LN, whereas under HN it ranged from 50 to 70 % in the first week of culture, decreasing to 10–15 % in the rest of the experimental period. Nitrogen uptake rate (NUR) ranged from 20 to 45 mmol N m−2 h−1 under HN, and 5 to 18 mmol N m−2 h−1 in LN treatments. Morphological and pigmentation changes were evident through the culture period. The thalli under HN were more reddish under the indoor treatments, than that in LN. The internal compounds increased throughout the experimental period. Mycosporine-like amino acids (MAAs) were accumulated under HN. N plays a photoprotective role due to both the increased photosynthesis and the MAA content. Maximal MAA productivity reached 113–253 mg MAAs m−2 d−1 under the O-HN treatment, the highest level reported until now in the bibliography. G. cornea could be used for bioremediation of high N content waters. In addition, under full solar radiation and high N availability produce high levels of bioactive compounds as MAAs, polyphenols and biliproteins for cosmeceutical applications.

The distribution of mycosporine-like amino acids in phytoplankton across a Southern Ocean transect

Interactions between phytoplankton and ultraviolet radiation (UVR: 280 – 400 nm) are undergoing changes dictated by variability in ocean temperature, the depth of mixed layers, nutrient availability, and the thickness of the ozone layer. There are a variety of mechanisms for phytoplankton to cope with UVR stress, one of the most prevalent being the presence of mycosporine-like amino acids (MAAs). Despite the importance of these molecules to phytoplankton fitness under UVR stress, knowledge of the diversity and distribution of these molecules in the world’s oceans is relatively limited. Here, the composition and distribution of MAAs in phytoplankton were examined in a transect across the Southern Ocean, crossing multiple fronts, from eastern New Zealand to the West Antarctic Peninsula in March and April of 2018. The highest concentration of MAAs (> 0.2 μg/L) was found between 50 and 60°S, as well as along a longitudinal gradient between 137.47 and 144.78°W. A strong correlation was found between a model of the preceding month’s UVR dosage experienced in the mixed layer and the ratio of MAAs to chlorophyll-a across the transect, indicating a relationship between the integrated history of light exposure and phytoplankton physiology. Haptophytes accounted for the majority of biomass north of the polar front (PF) and were strongly correlated with a diversity of MAAs. South of the PF a transition to a community dominated by diatoms was observed, with community composition changes strongly correlated to porphyra-334 concentrations. The data presented here provide a baseline for MAA abundance and association with specific phytoplankton taxa across the Southern Ocean amid a changing climate.

A Chemical Investigation of the Antioxidant Capacity of Extracts from Red Macroalga Gracilaria domingensis

Extracts that were obtained with solvents of increasing polarity (hexane, dichloromethane, methanol, 80% methanol, and water) from the red macroalga Gracilaria domingensis were evaluated by reducing power with ferric reduction antioxidant power (FRAP) and Folin–Ciocalteu (FC) assays, lipid peroxidation inhibition by β-carotene-linoleic acid assay, and metal chelating ability based on the iron-ferrozine system. The highest antioxidant capacity was reported for the hexane (Hx) extract by the FRAP, metal chelating, and lipid peroxidation inhibition assays. An activity-guided fractionation of the Hx extract was carried out for the identification of its active constituents. The primary components were the most active antioxidant compounds. Despite the high antioxidant activities, the Hx extract was not active in the FC assay. In this assay, the activities were found in the methanol (M) and 80% methanol (80M) extracts. The FC assay is commonly used to measure the total phenolic compounds. However, no phenolic compounds were detected by GC-MS and HPLC analyses in the M and 80M extracts. Thus, non-phenolic components influenced the FC assay. The M and 80M extracts showed high content of mycosporine-like amino acids (MAAs). A fraction contained two MAAs (porphyra-334 and shinorine) (156 mg GAE·g−1) showed a similar performance to the values that were found for well-known antioxidants (BHT = 156 mg GAE·g−1 and Trolox = 166 mg GAE·g−1) and 30 times higher than those of the original extracts (~5 mg GAE·g−1) in the FC assay. Thus, MAAs contribute to the antioxidant activities that were observed in the FC assay within the studied samples. Together, these results advance our understanding of the antioxidant properties of algal extracts.

The influence of predator community composition on photoprotective traits of copepods.

Trait expression of natural populations often jointly depends on prevailing abiotic environmental conditions and predation risk. Copepods, for example, can vary their expression of compounds that confer protection against ultraviolet radiation (UVR), such as astaxanthin and mycosporine‐like amino acids (MAAs), in relation to predation risk. Despite ample evidence that copepods accumulate less astaxanthin in the presence of predators, little is known about how the community composition of planktivorous fish can affect the overall expression of photoprotective compounds. Here, we investigate how the (co‐)occurrence of Arctic charr (Salvelinus alpinus) and threespine stickleback (Gasterosteus aculeatus) affects the photoprotective phenotype of the copepod Leptodiaptomus minutus in lake ecosystems in southern Greenland. We found that average astaxanthin and MAA contents were lowest in lakes with stickleback, but we found no evidence that these photoprotective compounds were affected by the presence of charr. Furthermore, variance in astaxanthin among individual copepods was greatest in the presence of stickleback and the astaxanthin content of copepods was negatively correlated with increasing stickleback density. Overall, we show that the presence and density of stickleback jointly affect the content of photoprotective compounds by copepods, illustrating how the community composition of predators in an ecosystem can determine the expression of prey traits that are also influenced by abiotic stressors.

Antioxidant potential of two Brazilian seaweeds in response to temperature: Pyropia spiralis (red alga) and Sargassum stenophyllum (brown alga)

Natural antioxidants found in macroalgae represent a significant protective role against oxidative damage. The antioxidant capacity responses to abiotic stresses allow understanding the tolerance and sensitivity of the species. Pyropia and Sargassum inhabiting the intertidal zone exhibit several antioxidant mechanisms against oxidative stress stimulated by environmental factors, such as thermal stress. In this study, we evaluated the antioxidant capacity under different temperatures of the red macroalga Pyropia spiralis and the brown macroalga Sargassum stenophyllum, associated with the composition of mycosporine-like amino acids (MAAs) and phenolic compounds. Antioxidant capacity was determined by four antioxidant assays (ABTS: 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid); DPPH: 2,2-diphenyl-1-picryl-hydrazyl; FRAP: ferric reducing antioxidant power, and metal chelating). Phenolic compounds content was assessed using Folin-Ciocalteau reagent and HPLC, and MAAs using HPLC. In both species, the ABTS assay was the most sensitive antioxidant assay. At low temperature (15 °C), P. spiralis exhibited the lowest EC50 (half maximal effective concentration) in the ABTS assay, the highest total antioxidant capacity index, and high content of MAAs (porphyra-334, shinorine, and palythine). For S. stenophyllum, the lowest EC50 value for ABTS assay was registered at 15 °C, and the lowest total antioxidant capacity index at 30 °C with high content of phlorotannins, probably phloroethols. The information provided by this research may be useful for the study of thermal tolerance and sensitivity in marine macroalgae as well as a template for further investigations of designing phytochemicals in marine macroalgae.

Monthly Variation and Ultraviolet Stability of Mycosporine-like Amino Acids from Red Alga Dulse Palmaria palmata in Japan

Mycosporine-like amino acids (MAAs) are the natural ultraviolet (UV)-absorbing compounds from micro- and macro-algae. The MAAs in algae change with the environmental conditions and seasons. We previously determined an efficient extraction method of MAAs from red alga dulse in Usujiri (Hokkaido, Japan) and revealed monthly variation of MAA in 2019. Dulse samples in 2019 for MAA preparation were suitable from late February to April. In this study, to confirm the suitable timings to extract MAAs from Usujiri dulse, we also investigated the monthly (from January to May) variation of MAA content in 2020. There were the most MAAs in the sample on 18 March (6.696 µmol g−1 dry weight) among the samples from January to May 2020. From two years of investigation, we deduce that samples of Usujiri dulse from late February to early April were suitable for MAA preparation. The UV stability of the two major purified MAAs in Usujiri dulse—palythine and porphyra-334—was tested. The two MAAs and 2-hydroxy-4-methoxybenzophenone were stable for up to 12 h under a 312 nm lamp at 200 µW cm−2, but 2-ethylhexyl-4-methoxycinnamate formed a cis/trans-mixture in a short time. The data in this study show the suitable sampling period for Usujiri dulse and the possible application for UV protection from food and cosmetics.