## 1 Introduction  
Unlike floral honeys, which derive from the nectar of flowering plants, honeydew honey is obtained by secretions of the living parts of plants or excretions onto them produced by sap-sucking insects. Honeydew honeys differ in chemical composition from nectar honeys [1] as well in the volatile composition and/or antioxidant activity. Screening of natural organic compounds that characterize these honey types is of particular interest because palynological analysis cannot be carried out [2]. _trans_-\(\beta\)-Methyl-\(\gamma\)-octalactone, a characteristic volatile compound of oak wood, is proposed as a chemical marker for the plant origin of oak honeydew honeys [2]. Other compounds such as aminoacetophenone and propylanisole can be considered characteristic of holm-oak honeydew honeys. 1-(2-Furanyl)-ethanoneone, butane-2,3-diol, 3-hydroxy-butan-2-one and 1-hydroxy-propan-2-one were suggested compounds for discrimination among nectar and honeydew honeys [1].  
Antioxidant capacity of different honeys varies by floral source [3] as well by processing and storage conditions [4,5]. Components that were identified and/or quantified as honey antioxidants included phenolic compounds, ascorbic acid, the enzymes glucose oxidase, catalase, peroxidase and others. Additional research on single phenolic and other compounds in honey indicate that the antioxidant capacity is due to combination of a wide range of honey active compounds beyond phenolics [6]. Many different methods are appropriate for assessing the antioxidant activity (FRAP assay (ferric reducing antioxidant power), DPPH (1,1-diphenyl-2-picrylhydrazyl) method, ORAC (oxygen radical absorbance capacity), TEAC (Trolox equivalent antioxidant activity) and others) and in most cases it is necessary to use several tests to obtain good reliability [7]. Little information is available on the potential antioxidant activity of the honey ultrasonic solvent extracts. In our previous research [8] we reported the scavenging ability of the series of concentrations of the _Amorpha fruiticosa_ honey ultrasonic solvent extracts and the corresponding honey samples that was tested by a DPPH assay. Approximately 25 times lower concentration ranges (up to 2 g/L) of the extracts exhibited significantly higher free radical scavenging potential with respect to the honey samples.  
_Quercus frainetto_ Ten. belongs to the oak species. The growth process of oak fruits is extremely rich in cycles of 5-8 years. At the point of natural reduction of overproduction of fruits, the sweet sap from fruits appears. Fruit sap starts to flow over the cuticle of the fruit often with a foamy appearance. Therefore, the corresponding honeydew can also be produced without the mediation of plant sucking insects. Oak honeybee volatiles from Spain were previously identified by a microscale SDE apparatus after dichloromethane extraction [2] and _trans_-\(\beta\)-methyl-\(\gamma\)-octalactone, a characteristic volatile compound of oak wood, was proposed as a chemical marker. This compound is well known in winemaking, because it is responsible for the oak aroma of barrel-aged wines [9].  
The scope of this research is to obtain new information of oak honeydew volatile organic composition by combined use of headspace solid-phase microextraction (HS-SPME) and ultrasonic solvent extraction (USE). In addition, the obtained USE extracts were tested by DPPH and FRAP assay for the first time in order to unlock their antiradical and antioxidant potential. DPPH and FRAP assay of the USE extracts were compared to the activity of the honeydew samples to obtain data of potential extra value of the solvent extracts, not just for organic analyses.