Antibacterial Properties of Lichens Parmelia sulcata and Parmelia vagans Extracts

Abstract

The objective of this study is to analyze the antibacterial properties of secondary metabolites extracted from lichens Parmelia sulcata and Parmelia vagans collected from the semi-deserts of Russia. Identifying these natural compounds that can inhibit proliferation of bacterial cells can enhance the development of antibacterial therapeutics. Acetone extracts of two lichens (P. sulcata and P. vagans) were prepared by using a Soxhlet apparatus. After drying the extracted solution, we added a known volume of acetone and rocked the flask for 10 minutes to dissolve the dry extract. We then transferred the dissolved solution to a 50-ml tube to get Fraction #1 and repeated this step to get multiple fractions. We first confirmed the antibacterial activity against Staphylococcus aureus by using a disk diffusion test from different fractions of the lichens. We assessed the antibacterial activity against S. aureus by using Resazurin Assay to measure the viability of the bacterial cells. Our experimental data from a disc diffusion test showed different sizes of inhibition rings around the pellets with lichen extracts from different fractions. The inhibition was also confirmed by Resazurin Assay which demonstrates that bacterial growth is inhibited differently by different fractions of lichen extracts. Our findings indicate that these lichen species produce at least two secondary metabolites that slow bacterial growth and proliferation. Future experiments will be focused on isolating and characterizing the antibacterial compounds from P. sulcata and P. vagans crude extracts. In summary, the lichen's secondary metabolites may be important for the development of novel antibacterial drugs.