The increasing challenge of marine biofouling, mainly due to barnacle settlement, necessitates the development of effective antifoulants with minimal environmental toxicity. In this study, fifteen derivatives of brusatol were synthesized and characterized using ¹³C-NMR, ¹H-NMR, and mass spectrometry. All the semi-synthesized compounds obtained using the Multi-Target-Directed Ligand (MTDL) strategy, when evaluated as anti-settlement agents against barnacles, showed promising activity. Compound 3 exhibited the highest anti-settlement capacity, with an EC₅₀ value of 0.1475 μg/mL, an LC₅₀/EC₅₀ ratio of 42.2922 (>15 indicating low toxicity), and a resuscitation rate of 71.11%, while it showed no significant phenotypic differences in the zebrafish embryos after treatment for 48 h. The toxicity screening of zebrafish also demonstrated the low ecotoxicity of the selected compounds. Furthermore, homology modeling of the HSP90 structure was performed based on related protein sequences in barnacles. Subsequently, molecular docking studies were conducted on HSP90 using these newly synthesized derivatives. Molecular docking analyses showed that most activated derivatives displayed low binding energies with HSP90, aligning well with the biological results. They were found to interact with key residues in the binding site, specifically ARG243, TYR101, and LEU73. These computational findings are anticipated to aid in predicting the enzyme targets of the tested inhibitors and their potential interactions, thus facilitating the design of novel antifoulants in future research endeavors.

This study investigated the diversity of cultivable marine myxobacteria from Weizhou Island in the Beibu Gulf of Guangxi, with a particular focus on strains exhibiting potential antibacterial activity and associated enzyme production. The Escherichia coli entrapment method and filter paper methods were employed for separation, followed by purification using sequential conversion techniques. Myxobacteria were identified through morphology characterization and 16S rRNA gene sequence analyses. The antibacterial activity against porcine pathogens was assessed using the plate confrontation method, and enzyme activity was evaluated through the plate assay method. From 13 island samples, 28 myxobacteria cultures were isolated, representing 13 species across 8 genera, predominantly Myxococcus. The antibacterial test showed remarkable activity in 9 myxobacteria strains. Cystobacter fuscus (GXIMD 01665c) and Myxococcus virescens (GXIMD 01661b) produced inhibition zones of 54.4?0.18 mm and 57.33?0.09 mm against E. coli L2 and E. coli 10, respectively. The enzyme activity experiment revealed that all 9 strains of myxobacteria could produce protease and cellulase, with 7 strains specifically producing chitinase, 6 strains producing amylase, and 4 producing lipase. These findings highlight the diverse antibacterial properties and enzymatic potential of myxobacteria from Weizhou Island. Strains GXIMD 01665c and GXIMD 01661b emerged as valuable microbial resources, holding great promise for further research and development.

Background: The search for environmentally friendly antifouling agents has led to an increased focus on marine natural products. Methods: This study investigated the antifouling potential of lipid fractions extracted from ten marine fungal strains isolated from the Beibu Gulf, China. The lipids were evaluated through a multi-level bioassay approach, including the inhibition of microfouling (against four fouling bacteria: Marinobacterium jannaschii, Vibrio pelagius, Vibrio rotiferianus, and Alteromonas macleodii), the prevention of macrofouling (inhibition of barnacle Amphibalanus reticulatus cyprid settlement), and long-term (90-day) marine field trials. Results: Eight lipid fractions demonstrated inhibitory effects against at least one bacterial strain. Five lipids significantly inhibited barnacle cyprid settlement, with half-maximal effective concentration (EC₅₀) values ranging from 0.21 to 1.81 µg/mL and exhibited low toxicity (half-maximal lethal concentration (LC₅₀) > 50 µg/mL). Notably, four lipid fractions maintained potent antifouling efficacy (>70% inhibition) throughout the 90-day field exposure. Chemical characterization via gas chromatography–mass spectrometry (GC–MS) revealed that the bioactive fractions were predominantly composed of fatty acids and their derivatives. Major identified compounds included palmitic acid, methyl palmitate, linoleic acid, dodecyl-9-ynyl chloroacetate, cis-13-octadecenoic acid, oleic acid, methyl 11,14-octadecadienoate, and (E)-9-octadecenoic acid methyl ester. Conclusions: This work represents the first comprehensive investigation of marine fungal lipids from the Beibu Gulf with multi-target antifouling properties, providing a theoretical foundation and practical candidate compounds for developing eco-friendly antifouling coatings.