Quantitative and qualitative variations in the essential oil of Rosa foetida Herrm. (Rosaceae) flowers as affected by different drying methods

Abstract

The effect of five drying methods on the essential oil content and composition of Rosa foetida Herrm. was studied for incorporation into a post-harvesting program for medicinal and perfumery industries. The drying methods tested were sun drying (SD), closed shade drying (CSD), oven drying at 40°C (OD40) and 60°C (OD60) and microwave drying (MD). The essential oils from fresh and dried samples were isolated by hydrodistillation and analyzed by a gas chromatography–flame ionization detector (GC–FID) and GC–mass spectrometry (GC–MS). The drying method had a significant effect on the essential oil content (w/w%) in the order of: CSD (0.28%) > SD (0.20%) > OD40 (0.18%) > OD60 (0.14%) > MD (0.05%). In total, twenty-three, thirteen, eight, twelve, ten and twelve constituents were identified and quantified in fresh, CSD, SD, OD40, OD60 and MD samples, representing 93.4%, 97.5%, 97.3%, 97.4%, 98.0% and 96.7% of the total oil, respectively. The major components of all samples were n-nonadecane (25.8–56.4%), n-heneicosane (16.7–24.4%), 1-hexadecanol (14.5–19.7%), n-tetradecanol (1.5–6.8%) and Z-octadecadienal (1.0–5.2%). Our results showed that the drying method not only had an effect on the number of chemical components, but also significantly influenced the proportion of various constituents.