Chemical profiling of Rhododendron tomentosum essential oils and phenolics during key growth stages

Rhododendron tomentosum is an evergreen shrub which belongs to the family of Ericaceae. This plant is known to have a rich phytochemical composition and accumulates essential oils, the composition of which varies according to scientific research [ 1 ]. The aim of this study was to evaluate the phytochemical composition of R. tomentosum during mass flowering and fruit ripening periods. The phenolic profile of R. tomentosum ethanol extracts was determined and included seven identified compounds: hyperoside, avicularin, quercetin, neochlorogenic acid, chlorogenic acid, catechin, and procyanidin A2. The quantities of the identified compounds varied between the samples collected during mass flowering and those collected during fruit ripening. Catechin (915.99 μg/g) and procyanidin A2 (1216.28 μg/g) were the dominant compounds in samples taken during the fruit ripening period. The other 5 compounds – hyperoside (863.21 μg/g), avicularin (1050.39 μg/g), quercetin (77.89 μg/g), neochlorogenic (1613.06 μg/g) and chlorogenic acids (1792.03 μg/g) – were found in higher amounts in samples taken during mass flowering. Analysis of the essential oils revealed that R. tomentosum samples collected during mass flowering contained 54 identified compounds, while samples collected during the fruit ripening stage contained 56. At different phenological stages of the plant, the predominant compounds found were the same as α-terpinyl acetate, isoascaridol and p-cymene, but their quantitative values differed, constituting respectively 26.95%, 23.43% and 14.29% during mass flowering and 28.95%, 25.89% and 10.74% of the identified components during fruit ripening. The results revealed that the phytochemical composition of R. tomentosum varies with the phenological period of the plant. Publication History Article published online: 05 March 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany