Steam distillation extraction kinetics regression models to predict essential oil yield, composition, and bioactivity of chamomile oil

Chamomile (Matricaria chamomilla L.) is one of the most widely spread and used medicinal and essential oil crops in the world. Chamomile essential oil is extracted via steam distillation of the inflorescences (flowers). In this study, distillation time (DT) was found to be a crucial determinant of yield and composition of chamomile essential oil, but not of the antioxidant capacity. Essential oil obtained at 30, 60, 90, 120, 180, 240, 360, 480, 600, and 720 min showed significant increase in oil yield with increasing DT, reaching a maximum of 3.1 g oil per 1000 g of flowers at 720 min. The major compounds that were identified and quantified were anethole, β-farnesene, spathulenol, α-bisabolol oxide B, α-bisabolone oxide A, chamazulene, α-bisabolol oxide A, and spiroether. β-farnesene showed a decrease in content with increasing DT, whereas α-bisabolol oxide A, spiroether, and chamazulene rapidly increased up to 240 min, after which it started to plateau showing negligible change. Anethole content showed a steady decrease over time from approximately 2.4% at 30 min to 0.54% at 720 min. Yields of spathulenol, α-bisabolol oxide B, α-bisabolol oxide A, α-bisabolone oxide A, chamazulene, and spiroether essential oil constituents expressed as g/100 g of dried chamomile inflorescences showed a steady increase that was described well by the Michaelis-Menton model. If higher concentrations of α-bisabolol oxide A and chamazulene, and higher oil yields are desired, chamomile flowers must be steam distilled for 480 min. However, if oil with high β-farnesene concentration is desirable, then chamomile flowers should be distilled for 30 min. Distillation time can be used as a modifier of chamomile essential oil yield and composition. The kinetics regression models developed in this study can be utilized to predict essential oil yield, and composition of chamomile oil.