Table of Contents
International Journal of Antibiotics
Volume 2014, Article ID 302182, 6 pages
Research Article

Protolichesterinic Acid: A Prominent Broad Spectrum Antimicrobial Compound from the Lichen Usnea albopunctata

1Agroprocessing and Natural Products Division, National Institute for Interdisciplinary Science and Technology (NIIST), Council of Scientific and Industrial Research (CSIR), Thiruvananthapuram, Kerala 695019, India
2Division of Crop Protection/Division of Crop Utilization, Central Tuber Crops Research Institute, Sreekariyam, Thiruvananthapuram 695017, India

Received 30 April 2014; Revised 2 June 2014; Accepted 15 July 2014; Published 10 August 2014

Academic Editor: Silvano Esposito

Copyright © 2014 Nishanth Kumar Sasidharan et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The aim of this study is to investigate the antimicrobial compounds present in the lichen Usnea albopunctata. Ethyl acetate extract was purified by silica gel column chromatography to obtain a major compound and the chemical structure was characterized by 1H-NMR, 13C-NMR, DEPT, 1H-1H COSY, HMQC, HMBC, UV, and HR-MS spectroscopic methods as protolichesterinic acid. The antimicrobial activity was estimated by determination of the minimal inhibitory concentration by the broth microdilution method and agar disc diffusion method against thirteen human pathogenic bacterial and four fungal strains. Protolichesterinic acid recorded significant broad spectrum antimicrobial property. The best antibacterial activity was recorded against K. pneumonia (0.25 μg/mL) and V. cholerae (0.5 μg/mL). Significant antifungal activity was recorded against T. rubrum (0.12 μg/mL), which is significantly better than the standard antifungal agent. Protolichesterinic acid is reported for the first time from Usnea albopunctata. Antifungal activity of protolichesterinic acid against medically important fungi is also reported for the first time. Thus the results of the present study suggest that protolichesterinic acid has significant antimicrobial activities and has the strong potential to be developed as an antimicrobial drug after further clinical evaluation.