Drying-induced changes in terpenoid composition in Rhododendron anthopogon leaves

Abstract

To access the drying impact on essential oil of Rhododendron anthopogon D. Don, leaves of the species were collected from alpine meadows of Tungnath (Uttarakhand Himalaya, India). Both the fresh and shade dried leaves were used for oil extraction through hydrodistillation method. The results showed that α-Humulene was the most abundant compound, accounting for 25.6 % and 21.23 % in fresh and dried leaves, respectively, followed by α-pinene (24.9 % and 19.6 %, respectively. Other compounds also showed notable amounts, such as 2-β-pinene (7.71 % and 4.85 % in fresh and dried leaves, respectively) and trans-caryophyllene (5.12 % and 6.40 %, respectively). Analysis also revealed that nonadecane, p-menth-1-en-8-ol, β-citronellol, and trans-carane were present only in the essential oil extracted from dried leaves. The results indicated that, the biosynthesis of terpenoids in R. anthopogon responded differently to leaf drying. The production of sesquiterpenoids and triterpenoids, as well as phenylpropanoids was unaffected by the drying process, continuing at similar levels in both fresh and dried leaves. However, the biosynthesis of terpenoid backbone was only detectable in the essential oil from dried leaves. The selective activation of metabolic pathways observed in response to desiccation stress highlights the potential for significant alterations in the essential oil's chemical composition and biological properties. Further research is required to elucidate the precise molecular mechanisms and environmental factors mediating this phenomenon.