Qualitative and quantitative changes in the essential oil of sage (Salvia hydrangea DC exBenth.) as affected by different drying methods

Salvia hydrangea is one of the medicinal plants belonging to Lamiaceae family. Medicinal plants can be marketed as fresh or dried products; however aromatic plants are often dried before extraction to reduce moisture content. The aim of this study was to evaluate the impact of different drying methods on qualitative and quantitative changes in essential oil of sage. To determine the effect of drying methods on qualitative and quantitative characteristics of the plant essential oil, samples were dried in sunlight, shade, mechanical oven at 65ºC and then compared with fresh samples. The essential oils of all samples were extracted by hydrodistillation and analyzed using GC and GC–MS. The results showed that different drying methods had significant effects on essential oil content. According to results fresh herbs had the highest essential oil content followed by shade drying, sun drying and oven drying samples, respectively. Significant changes in chemical compound amount of the essential oils were observed which associated with the drying methods. Significant differences occurred among several constituents in the extracted essential oils, including a-pinene, camphene, phellandrene, 1,8-cineole and bornylacetate. Drying of Salvia hydrangea aerial parts in the shade is more suitable for obtaining higher amount of oil yield and percentage of a-pinene and 1,8-cineole. Therefore, shade drying could be recommended for extraction of essential oil from this plant on an industrial scale.