1 Antifungal Antibiotics from Potential

thesis presents isolation and structure elucidation of twenty-five antifungal antibiotics. The compounds were isolated from four different microorganisms, which had all been found to suppress fungal pathogens in bioassays. Eight cyclic depsipeptides, enniatins, were isolated from the fungus Fusarium sp. F31. Four of them have not previously been isolated from natural sources. They inhibited Botrytis cinerea spore germination at levels down to 100 μg/ml. From the bacterium Pseudomonas sp. MF381-IODS, two linear polyene polyketides were isolated, pseudotrienic acids A and B, together with the known antifungals didehydro-deepoxirhizoxin, and pyrrolnitrin. The pseudotrienic acids inhibited Gram-positive bacteria at levels down to 70 μg/ml. The Pseudomonas sp. Ki19 strain produced four different dialkylresorcinols, of which two were new analogues. All four were active against fungi at levels down to 100 μg/ml, and also against Gram-positive bacteria down to 5 μg/ml. The actinomycete Kutzneria sp. 744 was found to produce a spectrum of nine di- and trichlorinated cyclic depsipeptides, containing several unusual amino acids. The trichlorinated compounds were significantly more active and inhibited fungi down to 60 μg/ml and Gram-positive bacteri