Comparison of the Essential Oil Composition of Wild <i>Rhododendron tomentosum</i> Stems, Leaves, and Flowers in Bloom and Non-bloom Periods from Northeast China

Abstract

The essential oils from wild Rhododendron tomentosum stems, leaves, and flowers in bloom and non-bloom periods from Northeast China were hydrodistilled and the chemical components were analyzed by gas chromatography and Gas chromatography-Mass spectrometry. A total of 52 constituents, accounting for 88.16-98.88 % of the oil yield, were identified from stem, leaf, and flower essential oils in bloom period; and 48 components which accounted for 94.40-98.21 % of the oil yield were found from stem and leaf essential oils in non-bloom period. The essential oils from different part and growth period revealed big differences both in composition and relative content. Predominant constituents in all oils were 4-thujene, 5-(1-methylethyl)- bicyclo[3.1.0]hex-3-en-2-one, α-thujenal and (-)-4-terpineol. The oils from stems, leaves, and flowers in bloom period were found to be the richest in (-)-4-terpineol (14.77 %), 4-thujene (27.49 %) and 4-thujene (49.51 %), respectively; oils from stems and leaves in non-bloom period were found to be the richest in hexanal (17.17 %) and α-thujenal (21.00 %), respectively. Principal component analysis demonstrated the significant difference in oil composition of R. tomentosum from different countries.