Disclosing the potential of Cupressus leylandii A.B. Jacks & Dallim, Eucalyptus globulus Labill., Aloysia citrodora Paláu, and Melissa officinalis L. hydrosols as eco-friendly antimicrobial agents
Antimicrobial resistance is a major global health concern, threatening the effective prevention and treatment
of infections caused by microorganisms. These factors boosted the study of safe and green alternatives, with hydrosols,
the by-products of essential oils extraction, emerging as promising natural antimicrobial agents. In this context,
four hydrosols obtained from Cupressus leylandii A.B. Jacks & Dallim, Eucalyptus globulus Labill., Aloysia citrodora Paláu
and Melissa officinalis L. were studied. Their chemical composition comprises neral, geranial, 1,8-cineole, terpinen-
4-ol, and oplopanonyl acetate, compounds with recognised antimicrobial activity. Concerning antimicrobial activity,
significant differences were found using different hydrosol concentrations (10–20% v/v) in comparison to a control
(without hydrosol), showing the potential of the tested hydrosols to inhibit the microbial growth of Escherichia coli,
Staphylococcus aureus, and Candida albicans. A. citrodora hydrosol was the most effective one, inhibiting 90% of E.
coli growth and 80% of C. albicans growth, for both hydrosol concentrations (p < 0.0001). With hydrosol concentration
increase, it was possible to observe an improved antimicrobial activity with significant reductions (p < 0.0001).
The findings of this work indicate the viability of reusing and valuing the hydrosols, encouraging the development
of green applications for different fields (e.g., food, agriculture, pharmaceuticals, and cosmetics).
Financial support through national funds FCT/MCTES (PIDDAC) to LSRE-LCM
(UIDB/50020/2020 and UIDP/00690/2020), ALiCE (LA/P/0045/2020), CIMO
(UIDB/00690/2020 and UIDP/00690/2020), and SusTEC (LA/P/0007/2021). FCT
for the SFRH/BD/148124/2019 Heloísa Helena Scorsato de Almeida research
grant. Pedro Crugeira thanks OleaChain (NORTE-06-3559-FSE14 000188) for his research contract. GreenHealth project (Norte-01-0145-FEDER-000042).
