The impact of sewage and wastewater pollution on marine ecosystems is of increasing concern due to the rapid accumulation of heavy metals in seaweeds inhabiting near-shore environments. Seaweeds can be severely damaged by heavy metals throughout their life cycles. Although the physiological and ecological effects of heavy metal exposure have been studied, there is limited research on their molecular responses. Ulva pertusa is a prevalent seaweed species in South Korea and is ecologically significant in coastal ecosystems. We utilized high-throughput RNA sequencing to analyze changes in the transcriptome profiles of U. pertusa under low concentrations of heavy metals (MPS) and high concentrations of copper (MPS-Cu) and cadmium (MPS-Cd). Differential gene expression analysis revealed that 53 (control vs. MPS), 27 (MPS vs. MPS-Cd), and 725 (MPS vs. MPS-Cu) genes were expressed differentially. Differentially expressed genes identified in our study included those with protective roles against oxidative stress and those involved in metal transport to the vacuole. Furthermore, exposure to heavy metal stress had a negative impact on the photosynthetic apparatus structural proteins of U. pertusa, resulting in photosynthetic inhibition. Moreover, exposure to high concentrations of copper resulted in the activation of carbon-related metabolism. These findings contribute to our understanding of the molecular mechanisms underlying heavy metal toxicity in U. pertusa.

Triglochin maritima, a salt-tolerant plant, has demonstrated antioxidant effects, the ability to prevent prostate enlargement, antifungal properties, and skin moisturizing benefits. This study aimed to explore the anti-melanogenic potential of the 70% ethanol extract of T. maritima (TME) along with its ethyl acetate (TME-EA) and water (TME-A) fractions. TME (10–200 µg/mL), TME-EA (1–15 µg/mL), and TME-A (100–1000 µg/mL) were prepared and applied to B16F10 cells with or without α-MSH for 72 h. MTT assays were used to assess cytotoxicity, and anti-melanogenesis activity was determined by measuring melanin content, conducting a tyrosinase activity assay, and evaluating the expression of melanogenesis-related genes and proteins via RT-PCR and Western blotting. HPLC-PDA was used to analyze TME and TME-EA. The IC₂₀ cytotoxicity values of TME, TME-A, and TME-EA without α-MSH, were 198.426 μg/mL, 1000 μg/mL, and 18.403 μg/mL, respectively. TME and TME-EA significantly decreased melanin and tyrosinase activity in α-MSH-stimulated B16F10 cells, with TME-EA showing comparable effects to arbutin, while TME-A showed no influence. TME-EA down-regulated melanogenesis genes (Tyr, Trp1, Dct, Mitf, Mc1r) and reduced CREB, p-38, and JNK phosphorylation while increasing ERK phosphorylation, suggesting the CREB/MAPK pathway’s role in the anti-melanogenic effect. Luteolin was identified as a potential active ingredient. TME-EA may serve as an effective cosmeceutical for hyperpigmentation improvement due to its anti-melanogenic properties.

Gymnodinium catenatum is a paralytic shellfish toxin (PST)-producing dinoflagellate that produces classical PSTs and hydroxybenzoate analogues known as GC toxins. Toxicological evaluation of GC toxins remains limited because certified reference materials (CRMs) and toxicity data are unavailable. This study applied the Neuro-2a (N2a) cell-based assay to evaluate PST functional toxicity in a Korean G. catenatum strain. The algal extract was analyzed by dose–response curve fitting to estimate total saxitoxin (STX)-equivalent toxicity, while GC1 & 2, GC3, and GC4 & 5, isolated from large-scale culture and structurally confirmed by NMR and LC-MRM-MS/MS, were evaluated to determine toxicity equivalence factors (TEFs). A clear sigmoidal curve yielded a functional toxicity of 3.7275 pg STX eq cell⁻¹, and TEFs followed the order GC3 > GC4 & 5 > GC1 & 2, with potency gaps considerably larger than previously reported receptor-binding differences. These findings support the N2a assay as a complementary approach for PST analogues lacking CRMs and suggest that receptor-binding affinity alone does not fully predict cellular functional potency. Although the proposed TEFs, obtained from single assays per preparation, are preliminary and assay-specific, this study provides the first functional toxicity estimates for GC toxins, contributing to the toxicological characterization of novel PST analogues.