The search for bioactive natural compounds, traditionally focused on terrestrial environments, has increasingly expanded to the seas and oceans, opening new frontiers for exploration. Among the diverse organisms inhabiting these ecosystems, marine phanerogams have emerged as a promising source of health-promoting bioactive compounds. This review highlights the distinctive chemical diversity of seagrasses including species such as Posidonia oceanica, Zostera marina, and Cymodocea nodosa, among others, and focusses on the growing interest in natural therapies as alternatives to conventional pharmaceuticals. Compounds such as polysaccharides or secondary metabolites such as polyphenol and flavonoids produced by marine plants exhibit a broad range of beneficial properties, including anti-inflammatory, antibacterial, antioxidant, and antidiabetic qualities. This review describes how these compounds can mitigate inflammation, promote skin health, and combat oxidative stress. Moreover, certain marine extracts have demonstrated potential to inhibit cancer cell growth and improve metabolic disorders like obesity and diabetes. The manuscript also discusses the potential of marine plant extracts in the development of novel therapeutic agents to address various illnesses, including infections, chronic diseases, and metabolic disorders. It emphasizes the need for further research to fully elucidate the mechanisms underlying the activity of these bioactive compounds and their potential therapeutic applications. In summary, this study highlights marine plants as a valuable reservoir for identifying organic molecules, paving the way for innovative advancements in medical and healthcare interventions.

Human activities increasingly threaten marine ecosystems through rising waste and temperatures. This study investigated the role of plastics as vectors for Vibrio bacteria and the effects of temperature on the marine sponge Sarcotragus spinosulus. Samples of plastics and sponges were collected during July, August (high-temperature period), and November (lower-temperature period). Bacterial growth and sponge responses were analysed using biochemical biomarkers. The results revealed a peak in colony-forming units (CFU), particularly of Vibrio alginolyticus, on plastics and sponges in August, followed by a decrease in November. In August, CFU counts of Vibrio spp. were significantly higher in sponges with poor external appearance (characterized by dull coloration and heavy epiphytic growth) but returned to levels observed in healthy sponges by November. Microplastics were detected in the tissues of both sponge groups, with higher concentrations found in affected specimens. Biomarker analyses revealed increased lysozyme, glutathione S-transferase, catalase, and superoxide dismutase activities in healthy sponges during August, while malondialdehyde levels, indicating oxidative damage, were higher in affected sponges. In conclusion, affected sponges exhibited elevated CFU counts of Vibrio spp. and reduced antioxidant and detoxification responses under elevated temperatures. These findings suggest that combined impacts of plastics and warming may pose significant risks to S. spinosulus in the context of global climate change.

There is a paucity of in vivo assays to investigate the potential deleterious effects of plastic-laden compounds in the gastrointestinal tract of mammals, compared to in vitro testing and ecotoxicity assays in marine organisms. This work aims to fill this gap through a comprehensive evaluation of the acute toxicokinetics and bioavailability of bisphenol A (BPA)-adsorbed medium-density polyethylene (PE) microplastics (MPs) (ca. 3000 μg BPA/g), with a mean particle size of 136 μm, which were administered via oral gavage at a mere 0.67 mg BPA/kg body weight for 24 h using a murine model. The determination of plasma BPA-glucuronide revealed that BPA associated with MPs (PE-BPA) is bioavailable to a similar extent to that of freely dissolved BPA, with Area Under the Curves (AUC) values of 1249 ± 182 and 928 ± 276 μg h·L^-1 for the 0 → 6 h interval (AUC_0→6h), and 3586 ± 526 and 2325 ± 634 μg h·L^-1 for the 0 → 24 h interval (AUC_0→24h), corresponding to PE-BPA and free BPA, respectively. Several biomarker assays of the small intestine and liver, and the investigation of the gut barrier function were conducted to elucidate the potential deleterious effects of PE-BPA as compared to BPA and PE alone. Acute exposure to PE-BPA increased the expression of the detoxification biomarkers multidrug resistance protein 1 (MDR1) and UDP-glucuronosyltransferase 2b1 (UGT2b1) in the jejunum, particularly when PE and BPA occurred together, likely due to the extended intestinal residence time of the BPA-laden MPs. Oxidative stress markers, such as superoxide dismutase activity, and inflammatory responses, evaluated by myeloperoxidase activity, were also elevated in the PE-BPA group, suggesting a defensive response but without evidence of oxidative damage as determined by the malondialdehyde levels. In conclusion, the findings suggest that BPA associated with MPs exhibits similar bioavailability than that of freely dissolved BPA, with the subsequent activation of detoxification pathways and inflammatory responses.

Bothus podas (wide-eyed flounder) is a benthic flatfish likely exposed to microplastic (MP) pollution. We investigated MP ingestion and associated physiological effects in wild B. podas collected from Mallorca (Balearic Islands), Spain. Markers of oxidative stress, detoxification, and immunity were quantified in intestinal, hepatic, and splenic tissues. MPs were observed in the gastrointestinal tracts of 87.5% of the 24 specimens analyzed, with an average of 3.8 ± 0.6 items per fish. Fiber-type MPs predominated in both the gastrointestinal tract (69.6%) and sediment samples (97%). Additionally, micro-Fourier transform infrared spectroscopy analysis confirmed that the majority of ingested MPs were composed of polyethylene, polypropylene, and polyester. Fish were categorized into low (<3 items) and high (≥3 items) MP groups based on the median number of plastic items found in the gastrointestinal tract to assess sublethal impacts. In the gut, high-MP fish exhibited significantly elevated activities of detoxification enzymes: ethoxyresorufin-O-deethylase (phase I) and glutathione s-transferase (phase II), along with increased antioxidant enzyme superoxide dismutase and inflammatory myeloperoxidase. Gut catalase and malondialdehyde (MDA) were not significantly different between groups. In liver tissues, no biomarkers differed significantly with MP exposure. In the spleen, lysozyme and alkaline phosphatase activities were significantly higher in high-MP fish, while splenic MDA remained unchanged. These results indicate that gastrointestinal MP exposure triggers local oxidative stress responses and systemic immune activation in B. podas. Overall, ingestion of environmentally relevant MP levels elicited detoxification and inflammatory responses without significant increases in MDA, an indicator of oxidative damage, highlighting the physiological stress imposed by plastic pollution on benthic fish.

The spread of the green macroalga Batophora occidentalis into shallow, sheltered Mediterranean systems may alter habitat structure and impose sublethal stress on resident habitat-forming species. We assessed whether the presence of B. occidentalis in the s’Estany des Peix lagoon (Formentera, Balearic Islands) is associated with physiological alterations in the perennial brown alga Cystoseira compressa. Samples of C. compressa were collected from areas with high (n = 8) and low (n = 8) abundance of B. occidentalis, and benthic cover was surveyed using 40 × 40 cm quadrats (n = 8 per area). Thermal monitoring indicated greater short-term variability inside the lagoon compared to the outer mouth. Biochemical assays showed that individuals from invaded patches exhibited significantly elevated antioxidant enzyme activities (superoxide dismutase and catalase), higher glutathione S-transferase activity and increased total polyphenol content, together with greater reactive oxygen species production. In contrast, malondialdehyde levels did not differ between areas, suggesting that enhanced antioxidant and detoxification responses may prevent detectable lipid peroxidation under the conditions studied. Habitat characteristics, notably higher availability of rocky substrate in invaded sectors, likely facilitate B. occidentalis establishment and modulate the interaction outcome. In conclusion, the coexistence with B. occidentalis was associated with a moderate oxidative challenge in C. compressa, within the environmental context of the invaded areas, and we recommend long-term studies to determine whether these sublethal responses translate into demographic effects.

Background/Objectives: The pervasive presence of microplastics (MPs) and plastic-associated chemicals has raised concerns regarding their potential effects on the central nervous system. Polyethylene (PE), widely used in food-contact materials, can carry bisphenol A (BPA), an endocrine disruptor with oxidative and neuroactive properties. Although both MPs and BPA can cross biological barriers, their acute effects on the prefrontal cortex (PFC) remain poorly understood. The aim of the study was to evaluate the acute impact of orally administered free BPA, free MPs, and BPA adsorbed onto PE MPs (PE–BPA) on oxidative stress, inflammation, and gene expression in the PFC of Wistar rats. Animals received a single dose of BPA, PE–BPA, PE alone, or vehicle. Methods: Biochemical and transcriptional analyses were performed to evaluate the antioxidant and inflammatory responses as well as the potential changes in synaptic-related gene expression. Results: BPA-containing treatments produced selective early molecular responses. Catalase (CAT) and glutathione S-transferase (GST) activities were significantly increased in the PE–BPA group, with GST being also elevated in the BPA-alone group, whereas superoxide dismutase (SOD), myeloperoxidase (MPO), and malondialdehyde (MDA) levels did not significantly change. Transcriptional analyses revealed upregulation of the antioxidant genes Nrf2 and CAT in the PE–BPA group. Co-exposure to BPA and MPs also altered synaptic markers, including decreased brain-derived neurotrophic factor (BDNF) and Sert along with increased Nr2A expression, while inflammatory gene expression remained unaffected. Conclusions: These findings indicate that acute co-exposure to BPA and PE microplastics elicits early antioxidant activation and selective synaptic-related transcriptional changes in the PFC, suggesting that MPs may modulate BPA-associated molecular responses in the brain.