Biotransformation of bromosesquiterpenes by marine fungi

Marine-derived fungi as biocatalysts

Marine microorganisms account for over 90% of ocean biomass and their diversity is believed to be the result of their ability to adapt to extreme conditions of the marine environment. Biotransformations are used to produce a wide range of high-added value materials, and marine-derived fungi have proven to be a source of new enzymes, even for activities not previously discovered. This review focuses on biotransformations by fungi from marine environments, including bioremediation, from the standpoint of the chemical structure of the substrate, and covers up to September 2022.

Biotransformation of sesquiterpenoids: a recent insight

Sesquiterpenoids have been identified as natural compounds showing remarkable biological activities found in medicinal plants. There is great interest in developing methods to obtain sesquiterpenoids derivatives and biotransformation is one of the alternative methods for structural modification of complex sesquiterpenes structures. Biotransformation is a great drug design tool offering high selectivity and green method. The present review describes a comprehensive summary of biotransformation products of sesquiterpenoids and its structural modification utilizing a variety of biocatalysts including microorganisms, plant tissue culture and enzymes. This review covers recent literatures from 2007 until 2020 and highlights the experimental conditions for each biotransformation process.

Biohydroxylation of (-)-ambrox®, (-)-sclareol, and (+)-sclareolide by whole cells of Brazilian marine-derived fungi

A screening was performed using nine marine-derived fungi as biocatalysts and the natural products (-)-ambrox® (1), (-)-sclareol (2), and (+)-sclareolide (3) in order to select the microorganisms able to catalyze the biooxidation of these compounds. It was observed that only the Aspergillus sydowii CBMAI 934, Botryosphaeria sp., Eutypella sp., and Xylaria sp. presented active oxidoreductases and catalyzed the regioselective hydroxylation in the natural products. The hydroxylated metabolites obtained were 1β-hydroxy-ambrox (1a) (14%, A. sydowii CBMAI 934); 3β-hydroxy-ambrox (1b) (17%, Botryosphaeria sp.; 11%, Eutypella sp.); 3β-hydroxy-sclareol (2a) (31%, Xylaria sp.; 69%, Botryosphaeria sp.; 55%, Eutypella sp.); 18-hydroxy-sclareol (2b) (10%, Xylaria sp.); and 3β-hydroxy-sclareolide (3a) (34%, Botryosphaeria sp.; 7%, Eutypella sp.). This is the first report of biohydroxylation of (-)-ambrox® (1), (-)-sclareol (2), and (+)-sclareolide (3) by whole mycelia of marine-derived fungi.

Lactones with methylcyclohexane systems obtained by chemical and microbiological methods and their antimicrobial activity

Eight new lactones (δ-chloro-, δ-bromo- and δ-iodo-γ-lactones), each with a methylcyclohexane ring, were obtained by chemical means from (4-methylcyclohex-2-en-1-yl) acetic acid or (6-methylcyclohex-2-en-1-yl) acetic acid. Whole cells of ten fungal strains (Fusarium species, Syncephalastrum racemosum and Botrytis cinerea) were tested on their ability to convert these lactones into other products. Some of the tested fungal strains transformed chloro-, bromo- and iodolactone with a methyl group at C-5 into 2-hydroxy-5-methyl-9-oxabicyclo[4.3.0]nonan-8-one during hydrolytic dehalogenation. When the same lactones had the methyl group at C-3, no structural modifications of halolactones were observed. In most cases, the optical purity of the product was low or medium, with the highest rate for chlorolactone (45.4%) and iodolactone (45.2% and 47.6%). All of the obtained compounds were tested with reference to their smell. Seven halolactones and the hydroxylactone obtained via biotransformation of halolactones with 5-methylcyclohexane ring were examined for their antimicrobial activity. These compounds were capable of inhibiting growth of some bacteria, yeasts and fungi.