Synthesis and release of fatty acids under the interaction of Ulva pertusa and Heterosigma akashiwo by stable isotope analysis

Comprehensive Phytochemical Analysis and Bioactivity Evaluation of Padina boergesenii: Unveiling Its Prospects as a Promising Cosmetic Component

Marine macroalgae, such as Padina boergesenii, are gaining recognition in the cosmetics industry as valuable sources of natural bioactive compounds. This study aimed to investigate the biochemical profile of P. boergesenii and evaluate its potential as a cosmetic ingredient. Fourier-transform infrared (FTIR), gas chromatography-mass spectrometry (GCMS), and high-resolution liquid chromatography-mass spectrometry quadrupole time-of-flight (HRLCMS QTOF) analyses were employed to assess the functional groups, phycocompounds, and beneficial compounds present in P. boergesenii. Pigment estimation, total phenol and protein content determination, DPPH antioxidant analysis, and tyrosinase inhibition assay were conducted to evaluate the extracts' ability to counteract oxidative stress and address hyperpigmentation concerns. Elemental composition and amino acid quantification were determined using inductively coupled plasma atomic emission spectrometry (ICP-AES) and HRLCMS, respectively. FTIR spectroscopy confirmed diverse functional groups, including halo compounds, alcohols, esters, amines, and acids. GCMS analysis identified moisturizing, conditioning, and anti-aging compounds such as long-chain fatty alcohols, fatty esters, fatty acids, and hydrocarbon derivatives. HRLCMS QTOF analysis revealed phenolic compounds, fatty acid derivatives, peptides, terpenoids, and amino acids with antioxidant, anti-inflammatory, and skin-nourishing properties. Elemental analysis indicated varying concentrations of elements, with silicon (Si) being the most abundant and copper (Cu) being the least abundant. The total phenol content was 86.50 µg/mL, suggesting the presence of antioxidants. The total protein content was 113.72 µg/mL, indicating nourishing and rejuvenating effects. The ethanolic extract exhibited an IC50 value of 36.75 μg/mL in the DPPH assay, indicating significant antioxidant activity. The methanolic extract showed an IC50 value of 42.784 μg/mL. Furthermore, P. boergesenii extracts demonstrated 62.14% inhibition of tyrosinase activity. This comprehensive analysis underscores the potential of P. boergesenii as an effective cosmetic ingredient for enhancing skin health. Given the increasing use of seaweed-based bioactive components in cosmetics, further exploration of P. boergesenii's potential in the cosmetics industry is warranted to leverage its valuable properties.

Metabolites and metabolic pathways associated with allelochemical effects of linoleic acid on Karenia mikimotoi

Linoleic acid (LA) shows great potential in inhibiting the growth of multiple red tide microalgae by disturbing algal physio-biochemical processes. However, our knowledge on the mechanisms of algal mortality at metabolic level remains limited. Herein, the response of K. mikimotoi to LA was evaluated using metabolomics, stable isotope techniques (SIT), and physiological indicators. Results showed that 100 μg/L LA promoted the growth of K. mikimotoi, which was significantly inhibited by 500 μg/L LA, along with a significant reduction of photosynthetic pigments and a significant increase of reactive oxygen species (ROS). SIT showed that LA entered algal cells, and 56 isotopologues involved in ferroptosis, carotenoid biosynthesis, and porphyrin metabolism were identified. Non-targeted metabolomics identified 90 and 111 differential metabolites (DEMs) belonging to 11 metabolic pathways under the 500 μg/L and 100 μg/L LA exposure, respectively. Among them, 34 DEMs were detected by SIT. Metabolic pathway analysis showed that 500 μg/L LA significantly promoted ferroptosis, and significantly inhibited carotenoid biosynthesis, porphyrin metabolism, sphingolipid metabolism, and lipopolysaccharide biosynthesis, presenting changes opposite to those observed in 100 μg/L LA-treated K. mikimotoi. Overall, this study revealed the metabolic response of K. mikimotoi to LA, enriching our understanding on the allelochemical mechanism of LA on K. mikimotoi.

Spectroscopic characterization of dissolved organic matter from macroalgae Ulva pertusa decomposition and its binding behaviors with Cu(II)

Dissolved organic matter (DOM) from macroalgae is regarded a crucial source of autochthonous DOM in coastal ocean. In the present study, the characteristics of DOM from the macroalgae Ulva pertusa decomposition (U. pertusa-DOM) and its binding behaviors with Cu(II) using multiple spectroscopic techniques and chemometric analyses. The labile U. pertusa-DOM could be consumed and transformed by microorganisms. The absorption spectroscopic descriptors indicate that the hydrophobicity, aromaticity, and molecular weight of the U. pertusa-DOM increase during the 27-day incubation period. Fluorescence excitation-emission matrix spectroscopy combined with parallel factor analysis suggests that the relative abundance of the protein-like component (C1) (96.10-84.96%) sequentially decreases, whereas the humic-like components (C2) (2.16-9.73%) and (C3) (1.75-5.31%) in the U. pertusa-DOM increase with the U. pertusa decomposition. The Cu(II) binding properties of the U. pertusa-DOM are dependent on the decomposition time. The order of the conditional stability constant (logK_M) is C2 > C1 > C3. The complexation capacity (f) of C1 is higher than those of C2 and C3 at a specific time. Synchronous fluorescence spectroscopy coupled with two-dimensional correlation spectroscopy reveals that the microbial degradation could accelerate the Cu(II) binding to humic-like fractions in the U. pertusa-DOM. These findings will help us better understand the biogeochemical behaviors of macroalgal DOM and heavy metal in coastal ecosystems.