Contents lists available at ScienceDirect Industrial Crops & Products journal homepage: www.elsevier.com/locate/indcrop Plant phenolic extracts as an effective strategy to control Staphylococcus aureus, the dairy industry pathogen Fernanda Gomes a, ⁎ , Natália Martins b,c , Lillian Barros b , Maria Elisa Rodrigues a , M. Beatriz P.P. Oliveira c , Mariana Henriques a , Isabel C.F.R. Ferreira b a CEB, Centre of Biological Engineering, LIBRO–Laboratório de Investigação em Biofilmes Rosário Oliveira, University of Minho, 4710-057 Braga, Portugal b Centro de Investigação de Montanha (CIMO), Instituto Politécnico de Bragança, Campus de Santa Apolónia, Bragança, 5300-253, Portugal c REQUIMTE/LAQV, Faculdade de Farmácia, Universidade do Porto, Rua Jorge Viterbo Ferreira, n° 228, Porto, 4050-313, Portugal ARTICLE INFO Keywords: Antibacterial activity Dairy food industry Phenolic extracts Staphylococcus aureus ABSTRACT Staphylococcus aureus is one of the most common contagious mastitis pathogens. Bovine mastitis is considered an important reservoir for dairy industry contamination, and therefore to ensure S. aureus control has gained a pivotal importance. Natural matrices present multiple biological effects, being its antimicrobial potential in- creasingly reported. Thus, the present study aims to assess the antibacterial activity of several methanol:water extracts, obtained from plants, against Staphylococcus aureus. Moreover, the most effective extract was char- acterized in terms of phenolic compounds, by using high performance liquid chromatography coupled to diode array and mass spectrometer detectors. Among the tested extracts, Eucalyptus globulus was the most effective against all tested S. aureus strains, followed by Juglans regia and Foeniculum vulgare. Inhibition halos of the plant extracts varied between 8.0–16.0 mm, excepting for F. vulgare in which two evident halos were observed: one with growth inhibition (5.0–7.0 mm) and a second one with visible cell density reduction (13.0–14.0 mm). Susceptibility assays evidenced that E. globulus extract exerted the highest antibacterial activity (MICs = 0.195–0.39 mg/mL), being effective against all the tested strains. Among the phenolic compounds identified in this extract, gallotannins, ellagic acid glycoside, and quercetin derivatives, were the most abundant; and therefore, may exert a positive and contributive effect to the observed antibacterial effect. Overall, the use of plant extracts to control bovine mastitis caused by S. aureus is a promising solution that could contribute to the reduction of the occurrence of dairy food industry contaminations, providing considerable benefits to agro- industries on the formulation of high-quality and safety dairy products. 1. Introduction Bovine mastitis is the most expensive disease for the worldwide dairy industries. The management of this pathology is mainly based on the extensive use of antibiotics/disinfectants (Pieterse and Todorov, 2010), which has triggered the development of complicated scenarios of antimicrobial resistance (Motlagh et al., 2013). Beyond the poor efficacy of the antibiotic treatment, bovine mastitis has become in- creasingly difficult both to control and mainly to eradicate in many herds (Carter and Kerr, 2003; Sutra and Poutrel, 1994). The increasing rates of antibiotic resistance hamper an urgent and effective bovine mastitis management, at the same time that motivate the search for effective antimicrobials (Rossi et al., 2011). Among the etiological agents for this complicated infection, Staphylococcus aureus is considered the most prevalent; moreover, and due to its zoonotic potential, a pivotal attention has driven an increasing solicitude by dairy industries (Kummel et al., 2016). Recently, Kummel et al. (2016) showed that S. aureus from bovine mastitis can enter in the dairy chain production via contaminated milk, which is in accordance with the previous study carried out by Sabour et al. (2004), who described the presence of antibiotic-resistant Staphylococcus species in milk proces- sing lines, associated with chronic mastitis. Based on these findings, it becomes of the utmost importance to discover more effective, safer and selective control strategies, not only to reduce the number of micro- organisms present in milking installations, but also to reduce the like- lihood of bovine mastitis and milk contamination occurrence. Natural matrices have been increasingly reported as effective al- ternatives to the current antimicrobial agents. In fact, the use of bota- nical preparation dates back from the beginning of human civilization, being effectively used in a wide variety of health conditions (Saranraj and Sivasakthi, 2014). As a rich source of bioactive molecules, among them phenolic compounds, natural matrices are commonly defined as https://doi.org/10.1016/j.indcrop.2017.12.027 Received 24 October 2017; Received in revised form 22 November 2017; Accepted 11 December 2017 ⁎ Corresponding author. E-mail address: fernandaisabel@deb.uminho.pt (F. Gomes). Industrial Crops & Products 112 (2018) 515–520 0926-6690/ © 2017 Elsevier B.V. All rights reserved. T