In vitro inhibitory activity of organic Thymus vulgaris CT borneol essential oil against Candida albicans

Abstract:

[Background] Candida albicans is a conditional pathogenic fungus capable of causing severe mucosal and systemic fungal infections and one of the major fungi leading to high morbidity and mortality in patients. [Objective] To study the inhibitory activity and mechanism of thyme essential oil against C. albicans. [Methods] The inhibitory zone diameters of 5 thyme essential oils against C. albicans were determined, and the components of the essential oils with high inhibitory activity were identified. Scanning electron microscope (SEM) was employed to observe the effect of essential oils on the morphology of C. albicans. The alkaline phosphatase (AKP) content and extracellular solution conductivity were determined, and propyl iodide (PI) staining was performed, on the basis of which the effects of essential oil on the biofilm formation and adhesion and the phospholipase activity of C. albicans were determined. In addition, real-time fluorescence quantitative PCR was conducted for the lectin-like sequence gene ALS4 involved in the biofilm formation, HWP1 involved in the switch from yeast growth to hyphal growth, and the phospholipase gene PLB1 to reveal the inhibitory mechanism of this essential oil on C. albicans. [Results] The Organic Thymus vulgaris CT borneol essential oil (TBEO) with the strongest inhibitory effect on C. albicans was selected, which showed the inhibition zone diameter was (36.0±4.8) mm. The main components of TBEO were α-terpineol (43.43%), camphene (8.97%), caryophyllene (7.70%), carvacrol (5.81%), and linalool (5.19%), which accounted for about 70% of the total TBEO. The results of SEM showed that TBEO caused concave surface and distorted cells of C. albicans. TBEO increased the permeability of the cell membrane and cell wall of C. albicans, causing the leakage of intracellular substances. TBEO inhibited the biofilm formation and exerted a scavenging effect on the formed biofilm of C. albicans. TBEO reduced mycelium formation, affected adhesion, and decreased phospholipase activity. Real-time fluorescence quantitative PCR results showed that TBEO significantly down-regulated the expression levels of HWP1, ALS4, and PLB1. [Conclusion] TBEO exerts an inhibitory effect on C. albicans. This study provides a theoretical basis for the application of TBEO in the prevention and control of C. albicans infection.