Essential Oil Yield, Composition, and Bioactivity as a Function of Distillation Time

Researchers reporting data on essential oil content and composition of various aromatic plants are utilizing different extraction methods and duration time. The essential oil of a number of aromatic crops is traditionally extracted via steam distillation. However, the optimal distillation time for most crops is largely uknown. Our previous research has shown that distillation time (DT) can modify essential oil yield and composition of several crops such as coriander (Coriandrum sativum L.), oregano (Origanum vulgare L.), peppermint (Mentha x piperita L.), Japanese cornmint (Mentha canadensis L.) lemongrass (Cymbopogon flexuosus Steud.), and palmarosa (Cymbopogon martinii Roxb.), pine (Pinus ponderosa Dougl. ex Laws), of female and of male Rocky Mountain juniper (Juniperus scopulorum Sarg.). We conducted additional research on the effect of DT on other crops including anise (Pimpinella anisum L.), wormwood (Artemisia annua L.), fennel (Foeniculum vulgare Mill), and lavender (Lavandula angustifolia Mill.). Herewith, we are presenting data from all the DT studies on the above crops. In all these studies, DT significantly changed both the essential oil yields and composition. In general, there was a trend for the low boiling oil constituents to be eluted first, while the main essential oil constituents for most of the plants required longer DT. The antioxidant capacity of the essential oils from different DT within a plant species was also altered. For some plant species, we developed regression models that can predict essential oil yield, the concentration of individual constituents, and the yield of these constituents within DT starting at couple of minutes and finishing with 8, 10, and 14 hours (different DT range for different crops). These studies demonstrated that DT can be used as a tool for obtaining essential oils with different composition, moreover, in some instance a specific targeted composition can be obtained. These studies also established the optimum length of the DT for maximum essential oil yields of the selected crops. In most instances, the optimal DT for maximum yields and desirable composition for a given species was shorter compared to what is usually used and reported by researchers and processors. Apparently, these shorter DT may translate into significant savings of energy for producers and processors. The data demonstrated that researchers must report the DT when reporting essential oil and composition of these crops. The data from these studies can help researchers when comparing reports in which different DT for extraction of essential oil from a specific crop were used.