determination of phenolic contents in rhododendron ponticum extracts

Species of the genus rhododendron (family ericaceae) are distributed across the northern regions of türkiye, with rhododendron ponticum being the most widespread. the leaves and flowers of rhododendron species have been traditionally used in many countries for the treatment of conditions such as the common cold, skin disorders, arthritis, bronchitis, asthma, and gastrointestinal diseases. the aim of the present study is to characterize the phenolic constituents of methanol extracts prepared from the leaves and flowers of rhododendron ponticum. rhododendron ponticum was collected zonguldak province, türkiye. the species and genus were taxonomically identified at the herbarium (voucher code: iste-118 950). separate methanol extracts were prepared from both the leaves and flowers using the soxhlet extraction method. the phenolic compound profiles of the extracts were analyzed by lc–hrms. analyses were performed on an exactive plus orbitrap instrument in both positive and negative ionization modes, and separations were carried out on a cosmosil 3c18-eb uhplc column under gradient elution conditions. samples were prepared in a methanol–water solvent system containing 0.5% acetic acid, filtered, and injected in triplicate for measurement. the use of both full scan and all ion fragmentation modes enabled structural confirmation of the compounds. in the leaf extract, the following compounds were identified: salicylic acid, 3-hydroxybenzoic acid, gallic acid, coumaric acid, caffeic acid, chlorogenic acid, quinic acid, 4-hydroxyphenylpropionic acid, catechin, epigallocatechin, rutin, quercetin, isoquercitrin, kaempferol, afzelin, nicotiflorin, myricetin, and eriodictyol. in the flower extract, salicylic acid, gallic acid, coumaric acid, caffeic acid, chlorogenic acid, quinic acid, 4-hydroxyphenylpropionic acid, catechin, rutin, quercetin, afzelin, nicotiflorin, myricetin, eriodictyol, protocatechuic acid, and daidzin were detected. among the leaf extract constituents, quinic acid, catechin, isoquercitrin, and rutin were the most abundant, whereas in the flower extract, quinic acid, chlorogenic acid, 4-hydroxyphenylpropionic acid, and daidzin were found to be the predominant compounds, respectively. the methanol extracts of rhododendron ponticum leaves and flowers contain a variety of phenolic compounds. these phenolic constituents differ between leaves and flowers in terms of both quantity and diversity.