## 1 Introduction  
Sisymbrium officinale (L.) Scop. (Brassicaceae) (SO) is an annual plant that is spread mostly in the Eurasiatic Region and North Africa. The plant is also commonly named \"hedge mustard\", \"erysimum\", or \"the singers' plant\", and it is known for its traditional use in the treatment of mild voice and respiratory discomfort. SO properties and uses has been recently reviewed [1]. The chemical markers [2] of SO are glucosionales (GLSs) and isothiances (ITCs), which are their main metabolic breakdown products, and these are also commonly found in many Brassicaceae. Historically, sulphured compounds are reported to stimulate mucosal secretion and expectation from the upper respiratory tract. [3]. The pharmacology of SO shows anti-inflammatory, analgesic, antitussive, myorelxant [4], a broad spectrum of antimicrobial [5] activity and also antimutagenic properties [6]. The effect of SO phyto-preparates on alleviating symptoms in patients with various degrees of vocal trait disability has been recently reported [7]. As in other plants of the Brassicaceae family, GLSs are present in SO with their corresponding ITCs, which are formed by enzymatic processes mediated by myrosinase and/or by chemical hydrolysis that could occur during the plant manipulation, storage, and processing. The relative content of GLSs and ITCs is often difficult to establish due to the transformations of the first into the latter in the same matrix. Moreover, the two classes of compounds have very different chemical features: polar GLSs are generally analysed by UV spectroscopy and/or HPLC-DAD, whereas gas chromatography-mass spectrometry (GCMS) is more suitable for volatile ITCs. The literature [8] identifies glucoputranjivin **1** (Figure 1) as the main glucosinolate in SO; its corresponding isothiamate is iso-propylisothiocyanate (IPITC, compound **2)**. Other GLSs as glucocochlearin **3**, glucojiabutin **5**, and sinigrin **7** are also present together with their congener ITCs, compounds **4** (sec-butylisothiocyanate, SBITC), **6** (isobutylisothiocyanate, IBITC) and **8** (allyl-isothiocyanate, AITC) [5; 9; 10]. Some of these compounds were previously identified in other plants as cochlearia [11] or rocket [12]. Compounds **1**-**8** are shown in Figure 1.  
A comparative analysis of GLSs in wild and cultivated SO has been recently published [13]. An extensive analysis of volatile compounds obtained by the hydrodistillation by GCMS was described and showed the presence of at least 42 different volatile compounds in SO, including several ITCs. Among volatiles, these compounds seem to be the most active from a biological point of view [5]. SO is commonly regarded as a medicinal plant, but some sporadic gastronomic uses are also reported; the plant is in fact a wild mustard, with a mild bitter and pungent taste profile, and it can be used likewise for food preparations. Recently, several food and drink preparations with SO have been described, including a \"voice drink\", a cold drink with SO, and other active ingredients for voice care [14]. SO and many other plants are recorded in the \"Herbs for Voice Database\", which is an open database of plants used for voice discomfort and airways pathologies [15]. The analysis of this database shows that the Transient Receptor Potential Ankyrin **1** (TRPA1) channel, which is involved in the somatosensory perception of pungency as well as in the nociception pathway of inflammatory pain, is the most represented molecular target for bioactive compounds in these plants. Compounds **2** and **4** from SO are in fact potent agonists in vitro of the TRPA1 channel [16]. Therefore, the analysis of these ITCs in SO become relevant to determine the fraction of volatiles that can contribute to the overall  
Figure 1: Glucosinolates (left) and isothi cyanates (right) previously identified in _Sisymbrium officinal_.