Antifungal activity of lichen extracts and compounds against Alternaria brassicola

Abstract

Alternaria brassicicola (Pleosporaceae) is destructive plant fungus causing black spot disease on virtually every important cultivated Brassica species including broccoli, cabbage, canola, and mustard [1,2. The pathogen is responsible for significant economic damage as infections may occasionally lead to 20 – 50% yield reductions in crops such as canola, mustard and rape. [2]. Furthermore A. brassicicola is a potent source of mold-derived allergens inducing chronic respiratory diseases such as asthma and chronic rhinosinusitis in humans. Lichens are complex symbiotic organisms consisting of fungi and cyanobacteria or algae. They are known to produce a large variety of unique secondary metabolites some exhibiting notable anti-inflammatory, antioxidant, antibacterial but also antifungal activities [3]. Despite the wide range of studied biological activities found in lichens, very little is known about their effect on A. brassicicola. The present study therefore evaluated the antifungal activity of lichen extracts and compounds on A. brassicicola using a nephelometry based method for measuring fungal growth [1]. Crude extracts of Lasallia pustulata (Umbilicariaceae), Ramalina fastigiata (Ramalinaceae), Evernia prunastri (Parmeliaceae) and Lobaria scrobiculata (Lobariaceae) were found to exhibit interesting inhibitory activities at 68.3, 42.5, 40.0 and 34.7 percent inhibition at 25 µg/Ml, respectively. Furthermore (+) usnic acid (1) (57.5% at 72.67µM) and m-scrobiculin (2) (32.5% at 59.8µM) showed notable antifungal effects.