Pleurotus ostreatus as a Biocatalyst to Obtain Bicyclic Hydroxylactones with Three or Four Methyl Groups

Antimicrobial Activity of Lactones

The development of bacterial resistance to antibiotics and the consequent lack of effective therapy is one of the biggest problems in modern medicine. A consequence of these processes is an urgent need to continuously design and develop novel antimicrobial agents. Among the compounds showing antimicrobial potential, lactones are a group to explore. For centuries, their antimicrobial activities have been used in folk medicine. Currently, novel lactone compounds are continuously described in the literature. Some of those structures exhibit high antimicrobial potential and some are an inspiration for design and synthesis of future drugs. This paper describes recent developments on antimicrobial lactones with smaller ring sizes, up to seven membered ε-lactones. Their isolation from natural sources, chemical synthesis, synergistic activity with antibiotics, and effects on quorum sensing are presented herein.

Antimicrobial chloro-hydroxylactones derived from the biotransformation of bicyclic halolactones by cultures of Pleurotus ostreatus

The aim of this research was to test the ability of cultures of edible fungi to biotransform three bicyclic halolactones. The substrates (2-chloro-, 2-bromo- and 2-iodo-4,4,6,7-tetramethyl-9-oxabicyclo[4.3.0]nonan-8-one) received by means of synthesis were transformed by oyster mushroom Pleurotus ostreatus and edible mushrooms of the genus Armillaria mellea, Marasmius scorodonius and Laetiporus sulfureus. The substrates were converted to hydroxyl derivatives only by the cultures of oyster mushroom. Out of seven strains of Pleurotus ostreatus - three were capable of hydroxylation of all substrates with the most effective conversion of chlorolactone. Bromo- and iodolactone were transformed to a small extent. Four new chloro-hydroxylactones were obtained as biotransformation products. The structures of substrates and products were established on the basis of spectroscopic data. Studies of antimicrobial activity performed on reference strains of pathogenic microorganisms showed that halolactones caused complete inhibition of growth of A. alternata and F. linii strains. On the other hand, chloro-hydroxylactones were able to completely inhibit the growth of A. alternata and F. linii strains and also C. albicans strain.