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Cinchona-based liquid formulation exhibits antifungal activity through Tryptophan starvation and disruption of mitochondrial respiration in Rhizoctonia Solani

Summary

Scientists discovered that a liquid extract from Cinchona bark, which contains quinine, can effectively kill a fungus that damages rice crops. The treatment works by blocking the fungus’s ability to absorb tryptophan (an important amino acid) and damaging its energy-producing mitochondria. When tryptophan was added back to the treatment, the fungus recovered, confirming this is the main way the extract works. This natural, plant-based approach could provide an eco-friendly alternative to chemical fungicides while reducing the risk of the fungus developing resistance.

Background

Rhizoctonia solani AG1-IA causes devastating sheath blight disease in rice crops, particularly in Southeast Asia, resulting in significant yield losses. Natural plant-derived antifungal compounds offer eco-friendly alternatives to synthetic fungicides. Cinchona bark, rich in quinoline alkaloids including quinine, has been traditionally valued for its bioactive properties.

Objective

This study investigates the antifungal properties and molecular mechanisms of a Cinchona-based liquid formulation (CBF) against Rhizoctonia solani. The research aims to identify the active compounds and elucidate the dual mechanisms of fungal inhibition to develop a resistance-manageable biopesticide.

Results

CBF demonstrated superior antifungal activity with an EC50 of 217.14 µg/mL, with quinine as the primary active alkaloid. Molecular docking revealed strong binding of quinine to fungal tryptophan transporters. Tryptophan supplementation reversed fungal growth inhibition, confirming tryptophan starvation as a mechanism. CBF elevated ROS levels, reduced mitochondrial membrane potential, downregulated Cytochrome P450, and increased electron transport chain gene expression.

Conclusion

CBF exhibits dual antifungal mechanisms through tryptophan starvation and mitochondrial respiration disruption, demonstrating robustness against resistance development. These findings support CBF as a promising eco-friendly biopesticide for sustainable management of rice sheath blight disease. The multiple modes of action suggest reduced risk of pathogen resistance development.
  • Published in:Scientific Reports,
  • Study Type:Experimental Research,
  • Source: PMID: 41203652, DOI: 10.1038/s41598-025-23347-7
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