## 1 Introduction  
_Brassicaceae_ plants have been an interesting research topic for years due to their chemical composition characterized by the presence of a variety of bioactive metabolites with valuable potential applications in improving nutrition and human health [1]. In recent years, our research team has focused on the study of taxa that grow spontaneously in Sicily (Italy) included in the _Brassicaceae_ family, with the aim of discovering new sources of bioactive compounds that could be used in the pharmaceutical, nutraceutical, and cosmetic fields. In a previous article, we reported the characterization of the phenolic and volatile components and the in vitro antioxidant properties of the aerial part hydroalcoholic extract of _M. incana_ subsp. _incana_ (L.[PERSON]. [2]. Based on the promising results obtained, it seemed interesting to extend our research to the other specific and intraspecific taxa comprised in the genus _Matthiola_ R. Br. endemic to Sicily. In particular, the intraspecific taxa of _Matthiola frucitulosa_ (L.) [PERSON] were selected for the current study. _Matthiola frucitulosa_ ([PERSON] [PERSON] (synonyms: _Cheiranthus frucitulosus_ L., _Matthiola tristis_ (L.) [PERSON]) is a perennial species that reaches up to 60 cm in height, sparsely pubescent to densely white to mentose, woody at the base. The leaves are linear or oblong, entire to sinuate-pinnatifid, and the flowers are gathered in terminal racemes with yellowish to purplish-violet petals. The fruit is a siliqua, erect or patent, more or less cylindrical [3; 4; 5]. _Matthiola frucitulosa_ is native to Southern Europe (Southeastern Europe: Albania, Bulgaria, Croatia, Greece, Italy, Macedonia, Montenegro, Serbia; Southwestern Europe: France, Portugal, Spain), Northern Africa (Algeria, Libya, Morocco, Tunisia), and Western Asia (Cyprus, Turkey) [3; 5; 6]. In the \"Flora Europaea\" and \"Flora Hellenica\", as well as in the consulted taxonomic database \"The Plant List\", three different subspecies are indicated under _M. frucitulosa_: the nominal subspecies (i.e., subsp. _fruticulosa_), subsp. _valesiaca_ (Gay ex Gaudin) [PERSON], and subsp. _perenn_ (P. Conti) [PERSON] [5; 7; 8]. On the other hand, in the latest edition of the \"Flora d'Italia\" only two intraspecific subdivisions are recognized for this taxon: the nominal subspecies, which prefers calcareous grounds, and the subsp. _coronopifolia_ (Sm.) Giardina and Raimondo (synonyms: _Cheiranthus coronopifolia_ Sm., _M. tristis_ var. _montana_ [PERSON], _M. tristis_ var. _bicornis_ Lojac., _M. frucitulosa_ var. _tricornis_ Lojac. ), which prefers clayey and marly substrates [3; 9]. Both subspecies occur in Sicily, as reported in the \"Checklist of the vascular flora of Sicily\" by [PERSON] et al. [4]. The use of _M. frucitulosa_ as a folk remedy has been documented: actually, its utilization in traditional medicine in Libya for the treatment of kidney stones and piles has been reported [10]. Despite this, as far as we know, in the literature there are no bibliographic data about the phytochemical composition and the evaluation of the biological properties of this taxon, except for the not very recent characterization of a few glucosinolates in the seeds and aerial parts of _M. frucitulosa_ collected in Spain [11]. These premises prompted us to design a study aimed at defining the phytochemical profile and the antioxidant properties of the hydroalcoholic extracts obtained from the aerial parts of both _M. frucitulosa_ infraspecific taxa growing wild in Sicily, namely, subsp. _fruticulosa_ and subsp. _coronopifolia_. A comprehensive insight into the qualitative-quantitative profile of the phenolic and the volatile constituents contained in the extracts was achieved by HPLC-PDA/ESI-MS and SPME-GC/MS analyses. Three different in vitro methods, which are based on different mechanisms, were used to assess the antioxidant activity. Lastly, the brine shrimp (_Artenia salina_ Leach) lethality bioassay was utilized to evaluate the toxicity of the extracts. Both intraspecific taxa of _M.