Tissue-specific accumulation of anti-inflammatory flavonoids in Rhododendron micranthum leaves

Rhododendron micranthum is a plant of traditional medicinal significance, commonly used to treat various inflammation- and respiratory-related conditions. Despite its known therapeutic value, comprehensive phytochemical profiling of its different tissues remains limited. Therefore, this study aimed to analyze and compare the distribution of phytochemicals in the leaves and stems of R. micranthum and to validate their corresponding anti-inflammatory properties. The phytochemical distribution was analyzed using high-performance liquid chromatography and liquid chromatography–electrospray ionization mass spectrometry. The anti-inflammatory activity was assessed by measuring nitric oxide (NO) production in lipopolysaccharide-stimulated RAW 264.7 macrophage cells. The leaves were found to be significantly enriched in flavonoids, while the stems accumulated higher levels of triterpenoids and coumarins, and exhibited higher flavonoid content than stems. The anti-inflammatory potential of these compounds was validated in lipopolysaccharide-stimulated RAW 264.7 macrophages, where leaf-enriched compounds, particularly trifolin ( 3 ) and avicularin ( 4 ), significantly inhibited NO production. These findings highlight the metabolic specialization of R. micranthum leaves and suggest their greater potential as a source of bioactive compounds for nutraceutical and cosmetic application. • Leaves of R. micranthum are the source of pharmacologically relevant flavonoids. • Leaf extracts inhibit nitric oxide production in macrophages. • LC–ESI/MS and HPLC identified key bioactive compounds in R. micranthum . • Although at low levels, trifolin and avicularin showed strong anti-inflammatory activity.