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

Summary

Scientists tested a plant-based extract from Cinchona bark as a natural fungicide against a serious fungus that damages rice crops. The active ingredient, quinine, works by two methods: it blocks the fungus from getting the amino acid tryptophan it needs to survive, and it damages the fungus’s energy-producing structures. When researchers added tryptophan back to the treated fungus, it recovered, confirming this is how the treatment works. This natural fungicide could offer farmers an eco-friendly alternative to chemical pesticides.

Background

Rhizoctonia solani AG1-IA causes sheath blight disease in rice, resulting in significant crop losses in Southeast Asia. Natural plant-based fungicides offer eco-friendly alternatives to synthetic fungicides which often promote resistance development. Cinchona bark contains quinoline alkaloids including quinine with reported antimicrobial properties.

Objective

To investigate the antifungal properties of a liquid Cinchona-Based Formulation (CBF) against Rhizoctonia solani and determine the underlying molecular mechanisms of fungal inhibition. The study examines the role of tryptophan starvation and mitochondrial dysfunction in the antifungal activity.

Results

CBF effectively suppressed mycelial growth (58.75%) with EC50 of 217.14 µg/mL, primarily through quinine (4.61% content). Molecular docking revealed strong quinine binding to amino acid permeases (−6.5 to −7.8 Kcal/mol). Tryptophan supplementation (400 µg/mL) reversed fungal growth inhibition, with amino acid permease expression increasing 4–9 fold. CBF elevated ROS levels and reduced mitochondrial membrane potential while modulating electron transport chain gene expression.

Conclusion

CBF demonstrates dual antifungal mechanisms through tryptophan starvation and mitochondrial respiration disruption in R. solani. The combination of mechanisms suggests CBF as a robust biopesticide with reduced resistance development risk. The findings support CBF as a promising eco-friendly alternative for long-term disease management in rice cultivation.
  • Published in:Scientific Reports,
  • Study Type:Experimental Study,
  • Source: PMID: 41203652, DOI: 10.1038/s41598-025-23347-7
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