Oxidative biotransformation of stemofoline alkaloids

Area of Science:

• Natural Product Chemistry
• Microbial Biotechnology
• Pharmacology

Background:

• Stemofoline alkaloids are complex natural products with potential bioactivity.
• Microbial biotransformation offers a sustainable route to generate novel chemical entities.
• Understanding structure-activity relationships is crucial for drug discovery.

Purpose of the Study:

• To investigate the microbial biotransformation of stemofoline and its derivatives using Cunninghamella elegans.
• To identify and characterize new stemofoline derivatives produced through biotransformation.
• To evaluate the acetylcholinesterase inhibitory activity of the parent compounds and their biotransformed products.

Main Methods:

• Fermentation of stemofoline, (2'S)-hydroxystemofoline, (11Z)-1',2'-didehydrostemofoline, and stemocurtisine with Cunninghamella elegans TISTR 3370.
• Isolation and structural elucidation of biotransformed products using spectroscopic techniques.
• Enzymatic assays to determine acetylcholinesterase inhibitory activity (IC50 values).

Main Results:

• Three new stemofoline derivatives (6R-hydroxystemofoline, (2'S, 6R)-dihydroxystemofoline, and (11Z,6R)-1',2'-didehydro-6-hydroxystemofoline) were identified.
• A known compound, 1',2'-didehydrostemofoline-N-oxide, was also produced.
• Stemocurtisine remained untransformed under the experimental conditions.
• The novel derivative 6R-hydroxystemofoline exhibited significantly enhanced acetylcholinesterase inhibition (IC50 = 11.01 µM) compared to its precursor stemofoline (IC50 = 45.1 µM).

Conclusions:

• Cunninghamella elegans effectively biotransforms stemofoline derivatives via C-hydroxylation and N-oxidation.
• Microbial transformation can enhance the bioactivity of natural products, as demonstrated by 6R-hydroxystemofoline.
• The study provides new insights into the metabolic pathways of stemofoline alkaloids and their potential as acetylcholinesterase inhibitors.