Qualitative and quantitative comparison of the essential oils of Citrus medica and Salvia officinalis prepared from fresh, freeze-dried and shade dried plant materials

Plants bearing essential oils contribute to prevent or cure diseases and maintaining health. Essential oil (EO) prepared from the leaves of Citrus medica showed antimicrobial activity while EO obtained from Salvia officinalis (Sage) is used as carminative, antispasmodic, antiseptic, astringent and for the treatment of many other diseases. Several studies were conducted to explore the effect of drying conditions on EO profile and quantity. In the current study, a comparison was performed for the EOs obtained from the fresh, freeze-dried and shade-dried samples of C. medica leaves and S. officinalis herbs prepared by hydro distillation and analysed by GC/MS. C. medica expressed a greater loss in oil contents upon drying especially in the monoterpenes with lighter molecular weights. The histological study did not show any features for water and volatile content preservation as it revealed thin cuticle, high stomatal index and oil glands just beneath the epidermis. Although S. officinalis expressed some loss of the essential oil in the freeze-dried samples, the shade-dried samples interestingly, demonstrated increase in the oil contents. Many factors participated in this phenomenon. Beside the histological features, slow drying permits continuation of the enzymatic activity for more time that expressed qualitative and quantitative impact on the oil contents.