Ascophyllum nodosum is a brown seaweed common in Arctic tidal waters. We have collected A. nodosum samples from the Barents Sea (BS), Irminger Sea (IS), and Norwegian Sea (NS) in different reproductive stages and have evaluated their biochemical composition, radical scavenging potential, and health risks. The total content of dominating carbohydrates (fucoidan, mannitol, alginate, and laminaran) ranged from 347 mg/g DW in NS to 528 mg/g DW in BS. The proportion of two main structural monosaccharides of fucoidan (fucose and xylose) differed significantly between the seas and reproductive phase, reaching a maximum at the fertile phase in the BS sample. Polyphenols and flavonoids totals were highest in NS A. nodosum samples and increased on average in the following order: BS < IS < NS. A positive correlation of free radical scavenging activity for seaweed extracts with polyphenols content was observed. The concentration of elements in A. nodosum from the Arctic seas region was in the following order: Ca > Mg > Sr > Fe > Al > Zn > As total > Rb > Mn > Ba > Cu > Co. Seaweeds from BS had the lowest metal pollution index (MPI) of 38.4. A. nodosum from IS had the highest MPI of 83. According to the calculated target hazard quotient (THQ) and hazard index (HI) values, Arctic A. nodosum samples pose no carcinogenic risk to adult and child health and are safe for regular consumption. Our results suggest that the Arctic A. nodosum has a remarkable potential for food and pharmaceutical industries as an underestimated source of polysaccharides, polyphenols, and flavonoids.

Introduction. Phlorotannins are secondary metabolites produced mainly by brown seaweeds and belong to the class of polyphenolic compounds with diverse bioactivities. Storm-cast brown algae, a problem for coastal biocenoses, may be a valuable source of polyphenols. The Folin-Ciocalteu reagent (FCR) is the most commonly used for the quantification of total polyphenols in natural samples. Different spectrophotometric methods with FCR for the determination of phlorotannins in algae have been described in the literature. Aim. The primary aim of this study is to standardize and validate the spec-trophotometric determination of total phlorotannins using FCR and demonstrate its applicability to analysis of storm-cast and fresh algae. Materials and methods. A. nodosum samples were collected in sheltered beach on the Olenitsa Bay (66°27'15.7"N 35°18'20.4" E), Kandalaksha Gulf (White Sea, Russia) on two tidal levels: one located at low tide at a depth of 0.6–1.0 m (fresh) and the second was located at the supralittoral in the zone of wave splashing (storm-cast). Field sampling was carried out between June and September. The cleaned seaweed were transported to the laboratory, washed accu-rately with clean water, freeze-dried, ground into powder. Functional groups present in the algae were identified using Fourier Transform Infrared (FT-IR) spectroscopy. Spectrophotometric determination of total phlorotannins content (TPhC) with FCR was used and validated according to national and international guidelines. Results and discussion. The optimum conditions for analysis time, wave-length, and standard substance were 45 min, 750 nm, and phloroglucinol, respec-tively. Under these conditions, validation by UV/Vis spectrophotometry proved the method to be linear ( R ² > 0.99), specific, precise, accurate, reproducible, robust, and easy to perform. The limit of detection and limit of quantification were 0.005 and 0.02 mg/mL, respectively. For precision analysis, an intra-day test (RSD 2.16 %) and an inter-day test (RSD 2.84 %) were performed. Matrix effect assessment demonstrated that this had a negligible effect (1.9 %) on the phlorotannins quantification. TPhC in storm-cast algae ranged from 59 to 101 mg/g, while freshly collected algae were statistically significantly higher ( p < 0.01) and ranged from 71 to 135 mg/g. Maximum accumulation of phlorotannins in A. nodosum was observed between July and August, after which a decrease was observed. Conclusion. Results of current study could be utilised for routine analysis of TPhC in brown algae and storm-cast seaweed using optimized spectrophotometric method with FCR on readily available low-cost equipment in most laboratories to provide rapid. This methodology complies with the requirements for pharmaceutical analysis to ensure the reliability of results during pharmaceutical development and routine control both in fresh and storm-cast of A. nodosum .

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Brown algae are a valuable renewable bioresource and are also important organisms to monitor due to anthropogenic impacts in the Arctic. In both cases, the content of natural elements and their potential seasonal variations are important knowledge for developing a monitoring program and planning biomass collection. The purpose of this work was a comparative study of the influence of the reproductive phase and biochemical characteristics on the elemental composition of Ascophyllum nodosum from the Barents Sea, the Irminger Sea and the Norwegian Sea. The content of polysaccharides (alginic acid, laminaran, fucoidan and mannitol) and 12 elements was studied. It was shown that the content of Fe, Al, Co, Cu correlates significantly in pairs, regardless of the presence of receptors in algae (r = 0.71–0.95, p < 0.05). It has been shown that the content of alginic acid significantly correlates with Co, Ca, Cu, As, Rb (r = –0.95, –0.89, –0.89, –0.88, –0.81, p ˂ 0.05, respectively) in sterile algae A. nodosum. Also for sterile individuals, a direct correlation of mannitol with Ca, Cu, Co, Rb, Sr, Al, Ba, Fe, Mn was noted (r = 0.98, 0.95, 0.93, 0.92, 0.91, 0.89, 0.82, 0.78, 0.76, р ˂ 0.05, respectively) and polyphenols with Zn (r = 0.94 at р ˂ 0.05) and As (r = 0.85 at р ˂ 0.05). For the first time, a direct correlation between the accumulation of alginic acid and fucoidan has been revealed for A. nodosum from the Arctic seas, which is not associated with the reproductive phase of the algae.

Storm-cast macroalgae represent a vast, underutilized biomass in the Arctic. This study evaluates the mineral composition, safety, and nutritional potential of storm-cast versus attached macroalgae from the Barents and White Seas to determine their suitability for commercial application. Mineral profiles (K, Na, Ca, Mg, As, Zn, Fe, Cu, Hg, Pb, and Cd) were determined by atomic absorption spectroscopy (AAS), while iodine (I) was analysed via iodometric titration. All elemental data were subsequently evaluated using ANOVA, principal component analysis (PCA), and hierarchical cluster analysis (HCA). Human health risks were assessed via Hazard Index (HI) and Lifetime Cancer Risk (LTCR) models based on the inorganic arsenic fraction. Storm-cast macroalgae exhibited a senescent post-detachment profile characterized by significant potassium and iodine leaching (p < 0.05) and iron enrichment from sediment entrapment. Despite leaching, iodine levels (up to 3.8 mg/g d.w.) satisfied pharmacopoeial minimums, though autumn White Sea samples exceeded the upper limit, necessitating blending with lower-iodine material. Toxic heavy metals remained below quantification limits, and total arsenic was well within regulatory thresholds. PCA confirmed that biomass physiological state is the primary driver of elemental variance. Adult consumption of storm-cast macroalgae was safe, whereas the pediatric HI exceeded 1.0. Overall, Arctic storm-cast macroalgae exhibit a high level of elemental purity, representing a promising raw material with a low chemical health risk for potential functional food and pharmaceutical applications.