# Exploring the Therapeutic Potential of Essential Oils of the Valdivian Rainforest (Drimys winteri and Laureliopsis philippiana) for Sustainable Udder Health in Dairy Systems

## TL;DR

This study explores essential oils from two native Chilean trees as natural treatments for bovine mastitis, showing promise in fighting bacteria and yeast.

## Contribution

The study identifies Canelo essential oil as a potential natural treatment for difficult-to-treat yeast mastitis in dairy cows.

## Key findings

- Canelo essential oil showed strong antibacterial and antifungal activity against mastitis-causing pathogens.
- Canelo oil was more effective than Tepa oil, especially against the azole-resistant yeast Pichia kudriavzevii.
- The oil's main active compounds are α-pinene and β-pinene, which contribute to its antimicrobial properties.

## Abstract

Bovine mastitis is a major health and economic constraint in dairy production and is commonly managed with antibiotics. However, intensive use of these drugs favors antimicrobial resistance, therapeutic failures and residues in milk, challenging One Health goals. In southern Chile, pasture-based herds are affected by bacterial mastitis mainly caused by Staphylococcus aureus and Streptococcus uberis, and, although far less common, also by fungal mastitis due to the azole-resistant yeast Pichia kudriavzevii. In this study, we investigated whether essential oils from two native Valdivian trees, Drimys winteri (Canelo) and Laureliopsis philippiana (Tepa), could inhibit these mastitis pathogens in the laboratory. We characterized their chemical composition and evaluated antibacterial and antifungal activity against clinical isolates from dairy cows with mastitis and type strains. Both essential oils showed inhibitory effects on S. aureus and S. uberis, but Canelo oil, rich in α-pinene and β-pinene, was consistently more active than Tepa. Notably, Canelo oil also exhibited clear inhibitory effects against P. kudriavzevii. Overall, our findings identify Canelo essential oil as a promising natural phytotherapeutic candidate for bovine mastitis, particularly for difficult-to-treat yeast mastitis, and justify further preclinical evaluation of formulations as adjuncts to conventional antimicrobial therapies in pasture-based dairy systems.

Bovine mastitis is a major bioeconomic and animal health challenge in dairy systems and is traditionally managed with intensive antibiotic therapy, contributing to antimicrobial resistance (AMR). This study explored the therapeutic potential of essential oils (EOs) from two native species of the Valdivian temperate rainforest, Laureliopsis philippiana (Tepa; LP_EO) and Drimys winteri (Canelo; DW_EO), against priority mastitis pathogens. Gas Chromatography–Mass Spectrometry (GC–MS) was used to characterize EO composition, and in vitro antibacterial and antifungal activities were evaluated against clinical isolates of Staphylococcus aureus, Streptococcus uberis and the azole-resistant yeast Pichia kudriavzevii by disk diffusion and broth microdilution assays. Both EOs were dominated by monoterpenes; LP_EO was richer in oxygenated monoterpenes (eucalyptol, terpinen-4-ol), whereas DW_EO showed a pinene-rich profile (β-pinene, α-pinene). DW_EO produced significantly larger inhibition zones than LP_EO against S. aureus and P. kudriavzevii and exhibited lower MIC50/MIC90 values for S. aureus, S. uberis and P. kudriavzevii. Notably, DW_EO showed a higher inhibitory activity against P. kudriavzevii with a MIC90 of 4 mg/mL. These findings support DW_EO as a high-potential dual-action phytotherapeutic candidate for developing formulations and complementary tools within sustainable bovine udder health and antimicrobial stewardship frameworks.