# Antifungal and anti-virulence activities of cinnamon, thyme, and clove essential oils against Candida species

## TL;DR

This study investigates how cinnamon, thyme, and clove essential oils can fight Candida infections by inhibiting fungal growth and reducing harmful traits like germ tube formation.

## Contribution

The study reveals that cinnamon and thyme oils are effective against drug-resistant Candida strains and reduce key virulence factors.

## Key findings

- Cinnamon and thyme essential oils showed strong antifungal activity, especially against drug-resistant Candida strains.
- Cinnamon EO reduced germ tube formation in C. albicans, while thyme EO completely inhibited it and induced pseudohyphae.
- Thyme EO suppressed protease production in C. auris clades II and III at low concentrations.

## Abstract

Candida species are major opportunistic pathogens, with Candida albicans being the most frequent cause of candidiasis. However, increasing rates of non-albicans infections and antifungal resistance bring an urgent need for new therapeutics. Essential oils (EOs) have gained attention due to their potential to inhibit fungal growth and virulence.

The chemical composition of cinnamon, thyme and clove EOs was analyzed by gas chromatography-mass spectrometry (GC-MS). Antifungal activity was evaluated against eighteen Candida strains representing nine species, including multidrug-resistant isolates. Minimum inhibitory concentrations (MICs) were determined. The two most active EOs were further assessed for their effects on germ tube formation and protease production, two key virulence traits.

GC-MS identified cinnamaldehyde, thymol and eugenol as the dominant components of cinnamon, thyme and clove EOs, respectively (> 70% relative abundance). All EOs displayed antifungal activity, with cinnamon and thyme being the most potent. Both oils showed increased activity against multidrug-resistant strains of Candida parapsilosis and Nakaseomyces glabratus compared with their susceptible parentals, suggesting they may target resistance trade-offs. All five clades of Candidozyma auris displayed low MICs for cinnamon EO (0.002-0.008% v/v), indicating high susceptibility. Cinnamon EO reduced germ tube formation in C. albicans from 97% to 12% at MIC/2, while thyme EO completely inhibited germ tube formation and induced pseudohyphae. Protease production was totally suppressed in C. auris clades II and III at MIC/2 thyme EO.

These results highlight the strong dual activity of EOs, supporting further exploration of their potential as complementary therapeutic options against Candida infections.