Dual modulation of toxic risks and functional benefits: How traditional practices enable safe consumption of toxic Rhododendron decorum Franch. in ethnic cuisine

Introduction The corollas of Rhododendron decorum Franch. have been used as a traditional ethnic food by the Bai nationality in Yunnan, China for centuries, with a well-preserved custom of removing the androecium and gynoecium prior to soaking, drying, and cooking. However, the molecular basis, nutritional value, and edible safety of this long-standing practice remain largely uncharacterized, limiting the development and utilization of this characteristic plant resource. Methods We integrate transcriptomic, metabolomic, and comparative metabolomic analyses to systematically characterize the molecular and metabolic profiles of distinct floral organs, geographically distinct populations, and fresh versus traditionally processed edible corollas of R. decorum Franch. Results and Discussion 3,463 differentially expressed genes (DEGs) and 165 differentially accumulated metabolites (DAMs) between corollas and androecium/gynoecium from Lijiang populations, and 3,229 DEGs and 145 DAMs from Heqing populations were identified, respectively. The flavonoid biosynthesis pathway showed the greatest divergence, with potentially risky flavonoids highly enriched in the androecium and gynoecium. Regional comparison revealed only the glycerophospholipid metabolism pathway was significantly co-enriched with DEGs and DAMs between edible corollas from the two regions, with no notable differences in other edible-related functional pathways. Traditional processing stably retained flavor-related L-histidine and S-(4-Methylthiobutylthiohydroximoyl)-L-cysteine, upregulated functional components p-coumaroyl quinic acid and taxifolin, and significantly downregulated potentially harmful flavonoids including (-)-epigallocatechin and myricetin. Conclusion This study systematically reveals the molecular basis of the Bai nationality’s traditional edible practice of R. decorum Franch., demonstrating that removing the androecium/gynoecium and traditional processing can effectively reduce edible risks while retaining flavor and functional active components. These findings provided critical scientific support for the food safety assessment.