Biosynthetic study of amphidinolide W

Area of Science:

• Marine Natural Products Chemistry
• Metabolic Pathway Elucidation
• Phylogenetic Analysis of Marine Microorganisms

Background:

• Dinoflagellates, such as Amphidinium sp., are prolific producers of complex secondary metabolites with diverse biological activities.
• Amphidinolides are a class of polyketide-derived macrolides isolated from dinoflagellates, with limited understanding of their specific biosynthetic origins.
• Strain Y-42 of Amphidinium sp. has previously yielded amphidinolide H, suggesting potential shared biosynthetic pathways with other amphidinolides.

Purpose of the Study:

• To determine the precise biosynthetic origins and assembly of amphidinolide W (1) in the dinoflagellate Amphidinium sp.
• To elucidate the incorporation patterns of acetate units into the carbon skeleton of amphidinolide W.
• To compare the biosynthetic pathways of amphidinolide W with that of the related amphidinolide H (2).

Main Methods:

• Enrichment of dinoflagellate cultures (strain Y-42) with isotopically labeled sodium acetate ([1-13C], [2-13C], and [1,2-13C2]).
• Analysis of 13C-enriched amphidinolide W using carbon-13 nuclear magnetic resonance ((13)C-NMR) spectroscopy to track label incorporation.
• Comparative analysis of acetate incorporation patterns between amphidinolide W and amphidinolide H.

Main Results:

• The (13)C-NMR data revealed that amphidinolide W is constructed from a hexaketide backbone, two additional acetate units, and four C1 units derived from the C-2 position of acetates, including four branched C1 units.
• Specific acetate incorporation patterns were identified for key carbon positions in amphidinolide W, such as C-1-C-2-(C-21) and C-8-C-18-(C-23, C-24).
• These incorporation patterns closely mirrored those observed for amphidinolide H (2), specifically at C-1-C-2-(C-27) and C-5-C-15-(C-28, C-29), suggesting a conserved biosynthetic machinery.

Conclusions:

• Amphidinolide W biosynthesis in Amphidinium sp. involves a complex assembly from a hexaketide precursor and multiple acetate-derived units.
• The study provides strong evidence for shared or highly similar biosynthetic pathways between amphidinolide W and amphidinolide H within the same dinoflagellate strain.
• These findings contribute to a deeper understanding of polyketide natural product biosynthesis in marine dinoflagellates and offer insights into the evolution of secondary metabolite pathways.