Modified Fusicoccane-Type Diterpenoids from Alternaria brassicicola.

Area of Science:

• Natural Product Chemistry
• Organic Chemistry
• Mycology

Background:

• Fusicoccane-type diterpenoids are a class of natural products with diverse biological activities.
• Alternaria species are known sources of various secondary metabolites, including diterpenoids.

Purpose of the Study:

• To isolate and characterize new modified fusicoccane-type diterpenoids from Alternaria brassicicola.
• To investigate the structural novelty and potential biological activities of these compounds.

Main Methods:

• Structure elucidation using Nuclear Magnetic Resonance (NMR) spectroscopy, High-Resolution Electrospray Ionization Mass Spectrometry (HRESIMS), and Carbon-13 NMR calculations.
• Absolute configuration determination via Electronic Circular Dichroism (ECD) calculations and single-crystal X-ray diffraction.
• Bioactivity screening for anti-inflammatory and cytotoxic effects.

Main Results:

• Seven new modified fusicoccane-type diterpenoids (1-7) and two known congeners (8-9) were isolated.
• Compounds 1-3 represent a rare class of 16-nor-dicyclopenta[a,d]cyclooctane diterpenoids.
• Compounds 2 and 4 possess novel tetracyclic 5/6/6/5 ring systems, and compound 5 features a novel tetracyclic 5/8/5/3 ring system.
• Compound 7 exhibited moderate anti-inflammatory activity.
• Compounds 2, 3, 5, and 7 displayed weak cytotoxicity.

Conclusions:

• The study expands the structural diversity of fusicoccane-type diterpenoids.
• Novel tetracyclic ring systems were discovered in diterpenoid chemistry.
• The isolated compounds show potential for further investigation into their biological activities.