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

Summary

Researchers synthesized compounds inspired by naturally occurring substances found in brown algae called phlorotannins. These synthetic compounds were tested against fungi that damage rice crops and other plants. Some methylated versions showed promise in slowing fungal growth, suggesting they could potentially be developed into new natural fungicides. However, the compounds were not effective against bacteria, indicating more research is needed.

Background

Phlorotannins are polyphenolic compounds from brown algae containing biphenyl and diphenyl ether motifs similar to antimicrobial phytoalexins. Dimeric phlorotannins such as fucols and phloroethols are difficult to isolate from their natural sources. Synthetic approaches offer a practical solution for obtaining these compounds for biological evaluation.

Objective

To design and synthesize natural and nature-derived biphenyls and diphenyl ethers with various methylation/acetylation patterns. To evaluate their antifungal and antibacterial activities against multiple phytopathogenic fungi and pathogenic bacteria. To establish structure-activity relationships for these compounds.

Results

None of the biphenyl derivatives showed significant antifungal activity. Polymethylated diphenyl ethers 10, 11, and 14 demonstrated 20-45% mycelium growth inhibition at 500 μM against tested fungal strains. Compound 15 inhibited appressorium formation in P. oryzae by 48%. All compounds showed MIC values between 128-256 μg/mL against bacterial strains, indicating low antibacterial efficacy.

Conclusion

Methylation patterns and the diphenyl ether linkage are critical for antifungal activity. The most promising derivatives were polymethylated diphenyl ethers rather than natural compounds. Further structural optimization is needed to enhance antifungal potency and develop antibacterial activity. The C-O-C fragment appears more favorable than C-C bonds for fungal target interaction.
  • Published in:ACS Omega,
  • Study Type:Experimental Research - Chemical Synthesis and Biological Evaluation,
  • Source: 10.1021/acsomega.5c02099, PMID: 40488058
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