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Nature-Inspired Biphenyls and Diphenyl Ethers: Design, Synthesis, and Biological Evaluation

Summary

Scientists created synthetic versions of protective compounds found in brown seaweed that could potentially be used as natural fungicides. They designed and synthesized fifteen different chemical derivatives and tested them against harmful plant fungi that damage crops. While the chemically modified versions showed modest effectiveness at stopping fungal growth, the naturally occurring compounds had little effect, suggesting that chemical alterations play an important role in fighting crop diseases.

Background

Phlorotannins are polyphenolic compounds found in brown algae with diverse bioactive properties. Dimeric phlorotannins (fucols and phloroethols) contain biphenyl and diphenyl ether motifs similar to antimicrobial phytoalexins produced by plants under stress conditions. Direct isolation from natural sources is impractical due to low yield and structural complexity.

Objective

To synthesize natural and nature-derived biphenyls and diphenyl ethers with various methylation and acetylation patterns, and evaluate their antifungal and antibacterial properties. The study aims to perform structure-activity relationship analysis and overcome challenges in natural product extraction.

Results

None of the biphenyl derivatives significantly inhibited fungal growth. Polymethylated diphenyl ethers (compounds 10, 11, and 14) showed 20-45% mycelium growth inhibition at 500 μM against all tested strains, with highest activity against Botrytis cinerea. No spore germination inhibition was observed except compound 15, which inhibited appressorium formation by 48%. All compounds showed MICs ≥128 μg/mL against bacteria.

Conclusion

Diphenyl ethers with polymethylated structures demonstrated moderate antifungal activity, suggesting that the methylation pattern and C-O-C linkage are crucial for biological target interaction. The natural unsubstituted compounds lacked significant antifungal activity. No antibacterial efficacy was detected, and further structural modifications are needed to enhance antimicrobial potential.
  • Published in:ACS Omega,
  • Study Type:Experimental Chemistry and Biological Evaluation,
  • Source: PMID: 40488058, DOI: 10.1021/acsomega.5c02099
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