Diversely Functionalised Cytochalasins through Mutasynthesis and Semi-Synthesis

Area of Science:

• Biochemistry
• Chemical Biology
• Mycology

Background:

• Cytochalasins are fungal metabolites known for their biological activities.
• Pyrichalasin H is a cytochalasin produced by Magnaporthe grisea.
• Modifying natural products can lead to novel compounds with altered or enhanced properties.

Purpose of the Study:

• To explore the mutasynthesis of pyrichalasin H to generate novel cytochalasin analogues.
• To investigate the chemical reactivity and biological activity of these new analogues.
• To develop new tools for visualizing intracellular actin.

Main Methods:

• Mutasynthesis of pyrichalasin H using Magnaporthe grisea NI980.
• Chemical modification of the synthesized analogues (e.g., halogenation, O-alkylation, azide formation).
• Reactions including Huisgen cycloaddition and palladium-catalyzed cross-coupling.
• In vitro and in vivo bioassays to assess cytotoxicity and antifungal activity.
• Actin-binding studies using adherent mammalian cells.
• Development of dye-linked cytochalasins for actin visualization.

Main Results:

• A series of unprecedented 4'-substituted cytochalasin analogues were synthesized with high yields.
• Halogenated, O-alkyl, O-allyl, O-propargyl, and 4'-azido analogues were successfully created.
• The 4'-halogenated and azido derivatives retained significant cytotoxicity and antifungal activities.
• A unique 4'-amino analogue was found to be inactive, and larger substituents attenuated bioactivities.
• Dye-linked cytochalasins enabled visualization of intracellular actin structures, showing filament-barbed end-binding specificity.

Conclusions:

• Mutasynthesis is an effective strategy for generating diverse cytochalasin analogues.
• The synthesized analogues retain biological activity and can be further functionalized.
• Dye-linked cytochalasins represent a novel class of tools for studying actin dynamics in living cells.