Abstract
Terpenoids such as geraniol and citral are known to have antibacterial, antifungal and anti-cancerous properties; however, their mechanism of action is least understood. In this study, the antifungal mechanism of monoterpene alcohol (geraniol) and monoterpene aldehyde (citral) was studied using Saccharomyces cerevisiae throughout 120 h duration and over a maximum tolerable dosage of 0.5% (v/v). Cell growth studies using optical density readings at 600 nm (ODλ=600 nm), Cell viability using MTT assay, Na+/K+ leakage into media, osmotic stress using flame photometry, detection of metabolites like dehydroergosterol (DHE), H2O2 using fluorescence spectroscopy, changes in functional group analysis using FT-IR, elemental analysis using EDAX, DNA damage using gel electrophoresis and cellular structural changes using SEM were carried out. Growth inhibition studies using ODλ=600 nm and MTT assays suggest that both geraniol and citral inhibited the growth kinetics significantly up to 0.1% v/v at and significantly increased beyond 0.1% at all the studied time points. Both the monoterpenoids induced the osmotic stress in S. cerevisiae measured as a change in reduction in pH, [H]+ concentration, with elevation in [Na]+ and [K]+ leakage into the media. Geraniol treatment reduced the levels of metabolites, dehydroergosterol (DHE) and H2O2, in a time-dependent manner whereas citral only affected their levels at 120 h. Energy dispersive X - ray spectroscopy (EDAX) studies suggest that both the monoterpenoids treatment differentially modulated the cellular elemental contents. Geraniol (0.03% v/v) and not the citral treatment induced DNA damage. Cellular structural analysis showed that both monoterpenoids have differential damaging effects to S. cerevisiae. This study shows that having an aldehyde and alcohol group on the terpenoids strongly affect the anti-fungal activity.