Antibacterial and Anti-Inflammatory Activities of Hydroalcoholic Extract and Nanoemulsion of Laurencia caspica Algae

Background Red seaweeds of the genus Laurencia are recognized as rich sources of novel bioactive compounds. In this study, we investigated the antibacterial and anti-biofilm properties of Laurencia caspica nanoemulsion (NLC), along with the immunomodulatory effects of its crude extract (LC) on murine macrophage cells (RAW264.7; NCBI C639). Methods The NLC was synthesized via ultrasonication and characterized by scanning electron microscopy (SEM) and dynamic light scattering (DLS) to determine particle size and morphology. The chemical composition of LC was analyzed using gas chromatography-mass spectrometry (GC-MS). In addition, the total polyphenol content was determined using standard colorimetric methods. The antibacterial and anti-biofilm activities of both LC and NLC were evaluated against Streptococcus mutans (ATCC 35668), while the anti-inflammatory potential of LC was assessed in LPS-stimulated RAW264.7 cells. Results GC–MS analysis revealed the presence of a major phenolic compound among the constituents of the L. caspica extract. The total phenolic content of LC was 21.5 ± 0.4 mg/ GAE g of extract. Our findings revealed that L. caspica extract inhibited RAW264.7 macrophage cell proliferation with an IC₅₀ value of 0.8 ± 0.02 mg/mL. At IC₁, IC₁₀, and IC₅₀ concentrations, LC significantly downregulated the expression of pro-inflammatory cytokines IL-6 and COX-2. The nanoemulsion form (NLC) exhibited stronger antibacterial activity, with a minimum inhibitory concentration (MIC) ranging from 0.08 to 5.7 mg/mL. Moreover, both LC and NLC effectively suppressed the adhesion of Streptococcus mutans biofilm, with NLC showing superior efficacy. Conclusions These findings suggest that L. caspica extract and its nanoformulation possess antimicrobial, anti-biofilm, and immunomodulatory properties. Further studies are needed to elucidate the molecular mechanisms underlying these biological effects and to explore the therapeutic potential of L. caspica -derived compounds.