Influence of Different Drying Methods on the Composition and Antimicrobial Activities of Essential Oil from Leucosidea sericea Eckl. & Zeyh.

Abstract

The composition of essential oil from the leaves of Leucosidea sericea and the impact of drying methods (air, sun, oven and microwave) on yield, composition, antibacterial and antifungal activities of the oil was studied. A total of 7 compounds were identified from both the fresh and air dried leaves, while 37 and 13 compounds were identified from sun and oven dried leaves respectively. The essential oil from fresh leaves was dominated by monoterpenes with α-pinene as the dominant compound in both fresh and air dried leaves (95.82 and 96.27% respectively), but its percentage was significantly reduced in the oil obtained from oven dried leaves (58.66%) and it was not detected in sun dried leaves. Sun drying the leaves resulted in the highest number of compounds with dominant ones being by β-pinene (31.50%), limonene (9.82%), isopinocarveol (8.76%), p-menth-1-8-ol (7.03%) and α-thujone (7.00%). Microwave oven drying led to a total loss of volatile compounds, whereas sun drying the leaves lead to a significant change in the composition of the essential oil. The study showed that drying the leaves at higher temperatures (oven and microwave) led to a significant reduction in essential oil yield. Antibacterial activity of the oil showed remarkable activity against both Gram-positive and Gram-negative bacteria, as well as four fungal species used in the study. The antimicrobial activity of the essential oil can be attributed to the presence of major components such as α-pinene, β-pinene, and limonene.