Simultaneous Extraction of Essential Oils and Flavonoids from Onions Using Turbo Extraction-Distillation Dima Mnayer & Anne-Sylvie Fabiano-Tixier & Emmanuel Petitcolas & Karine Ruiz & Tayssir Hamieh & Farid Chemat Received: 11 February 2014 /Accepted: 23 April 2014 # Springer Science+Business Media New York 2014 Abstract A simultaneous turbo hydrodistillation (THD) ex- traction of essential oil (EO) and flavonoid contents from onion (Allium cepa L.) was studied. Optimization of EO extraction was performed, and the effectiveness of THD in the extraction of onion total phenol content (TPC), total quer- cetin (TQ), quercetin aglycon (QA), quercetin-3,4 ′ - diglucoside (QDG), quercetin-4′-monoglucoside (Q4G), quercetin-3-monoglucoside (Q3G), and kaempferol (KMF) was evaluated and compared with conventional solvent ex- traction of fresh onion. THD offers valuable extraction of onion by-products: 68.90 g/t of EO, 95.86 % of total phenol, and 55.94 % of total quercetin contents. The conventional extraction of fresh onion allowed the presence of QDG (684.78 mg/100 g dry weight (DW)) and Q4G (423.44 mg/ 100 g DW), whereas QA, Q3G, and KMF were also present in onion by-products obtained by THD. At 180-min THD pro- cess, the highest phenol content was obtained in the aqueous phase (47.58 mg quercetin equivalents/g DW). QDG (315.29 mg/100 g DW) and Q4G (335.05 mg/100 g DW) were mainly present in the aqueous phase, whereas QA (271.79 mg/100 g DW) was mainly present in the solid phase. Q3G and KMF were detected in minor quantities in onion extracts. Keywords Turbo hydrodistillation extraction . Onion by-products . Essential oil . Flavonoids Introduction The human biological system is vulnerable to the attack of extremely reactive oxygen species (ROS), which are produced continuously as a result of endogenous enzymatic reactions and also by exogenous sources (Stajner and Varga 2003; Subhasree et al. 2009). The formation and activity of these ROS are believed to be responsible for degenerative diseases and their associated complications such as cancers, cardiovas- cular diseases, and accelerated aging of organisms (Singh et al. 2009). Increased consumption of diets rich in fruits and vegetables is associated with low prevalence of degenerative diseases as they provide a great amount of antioxidant phyto- chemicals. Literature proved antioxidants as one of the de- fense mechanisms within the organism against ROS (Boivin et al. 2009). These antioxidants (phenols, essential oil, etc.) act as free radical scavengers and offer protection against cellular damage by retarding oxidative stress. Among vegetable polyphenols, the flavonoids group generally dominates and is found relatively in higher concentration like sugar conjugates as studied by Miean and Mohamed (2001) in 62 edible plants detecting abundant amount of quercetin gluco- sides in different vegetables. Onion (Allium cepa L.), a versatile vegetable of the Alliaceae family, is appreciated worldwide not only for its distinctive taste and flavor but also for its significantly bene- ficial compounds. Several studies revealed the presence of various dietary flavonoids in different varieties of onions along with other bioactive compounds (Lachman et al. D. Mnayer : A.<S. Fabiano-Tixier (*) : E. Petitcolas : K. Ruiz : F. Chemat Université d’Avignon et des Pays du Vaucluse INRA UMR 408, GREEN Team Extraction, 84000 Avignon, France e-mail: anne-sylvie.fabiano@univ-avignon.fr D. Mnayer : T. Hamieh Faculty of Agricultural Engineering and Veterinary Medicine, Lebanese University, Dekwaneh, Lebanon T. Hamieh Laboratory of Materials, Catalysis, Environment and Analytical Methods (MCEMA), Faculty of Sciences, Doctoral School of Sciences and Technology (EDST), Lebanese University, Beirut, Lebanon Food Anal. Methods DOI 10.1007/s12161-014-9884-9