## 1 Introduction  
_C. cardunculus_ L. is a Mediterranean halophyte, commonly designated as cardoon, belonging to the Asteraceae family [1, 2]. It comprises three botanical varieties: var. allilis DC, var. scolymus ([PERSON]) [PERSON], and var. sylvestris (Lamk) Fiori [2]. Traditional applications of _C. cardunculus_ include the use of the blanched leaves and fleshy leaf petioles in soups, stews, and salads [3]. Flowers of _C. cardunculus_ are rich in proteases, namely cardosins A and B, and aqueous extracts of _C. cardunculus_ inflorescence have been used for centuries (particularly in Mediterranean regions) as coagulants in traditional ewes' milk cheese making, providing distinctive characteristics of texture and flavor in cheeses. In some well-known protected designation of origin (PDO) Portuguese cheeses, such as \"Serra da Estrela\", \"Castelo Branco\", \"Azetiao\", \"Evora\", \"Niza\" and \"Serpa\", the _C. cardunculus_ inflorescences, specifically their stigma, are used for their high content of aspartic proteasesand high milk-clotting activity [4]. Many studies support the important role of _C. carduculus_ in human nutrition, due to its high content of nutraceutical and bio-active compounds such as inulin and antioxidant phenolics [2; 5]. Furthermore, _C. carduculus_ extracts have shown hepatoprotective, anti-tumour [6], antibacterial and anti-HIV activity and the ability to inhibit cholesterol biosynthesis [7] and LDL oxidation [3]. The decoction extracts have several phenolic acids [8; 9] like chlorogenic acid, cynarine and some flavonoids like luteolin glycosyllated [10]. The literature has already described _C. carduculus_ var. scolymus (L.) leaves extract as having antimicrobial activity [11], however the use of these extracts on Gram-negative bacteria requires high concentrations to have an antimicrobial action [12]. The inflorescence of _C. carduculus_ L. has been the subject of several studies [13; 14]. The literature reports the chemical identification and antimicrobial activities of extracts of _C. carduculus_ L. obtained from extractions with organic solvents. Nevertheless, in this work, we intend to study the antimicrobial activity of extracts of aqueous nature from both infloresence and leaves of _C. carduculus_ L. against bacteria mainly belonging to the genus _Pseudomonas_ spp. isolated from cheese and/or the cheese making environment.  
Brownish pigmentation was described as a problem in cheese made from raw milk from sheep or goats [15; 16]. It has been reported by cheese producers to cause severe economic losses, since it is difficult to enter in the food market [15; 16]. _Pseudomonas_ spp. have been isolated from the mind of brownish cheese in several environments, producing extracellular molecules like enzymes [17] and biopigments [18].  
The inflorescence of _C. carduculus_ L. is already used in the traditional production of cheese as milk coagulant. To contribute to the sustainable use of the _C. carduculus_ L. plant, the main purposes of this study are the chemical characterization of aqueous leaves extract by mass spectrophotometry, the evaluation of the antimicrobial activity of _C. carduculus_ L. extracts against bacteria strains isolated in dairy industries, and the evaluation of the influence of _C. carduculus_ L. extracts in terms of inhibition of brown pigmentation.