Cyclofarnesoids and methylhexanoids produced from β-carotene in Phycomyces blakesleeanus.

Area of Science:

• Biochemistry
• Mycology
• Natural Product Chemistry

Background:

• Apocarotenoids are derived from β-carotene cleavage in Mucorales.
• These compounds are absent in β-carotene-deficient mutants, serving as markers.
• Three families of apocarotenoids are recognized: methylhexanoids, trisporoids, and cyclofarnesoids.

Purpose of the Study:

• To identify and characterize apocarotenoids in Phycomyces blakesleeanus cultures.
• To propose biosynthetic pathways for cyclofarnesoids and methylhexanoids.
• To investigate the influence of mating and culture conditions on apocarotenoid levels.

Main Methods:

• Liquid chromatography (LC), UV absorbance, and mass spectrometry (MS) for detection.
• Infrared (IR) and Nuclear Magnetic Resonance (NMR) spectroscopy for structural identification.
• Bioconversion studies using β-apo-12-carotenol and analysis of time-course and mating effects.

Main Results:

• Thirty-two apocarotenoids were detected, with eighteen identified, including four new compounds like 4-dihydrocyclofarnesine S.
• A classification scheme for Mucorales apocarotenoids was developed, suggesting metabolic pathways.
• Mating significantly increased methylhexanoid and cyclofarnesoid levels, particularly cyclofarnesine S in older cultures.

Conclusions:

• Novel apocarotenoids were discovered, expanding the known diversity of these compounds.
• Proposed biosynthetic pathways for cyclofarnesoids and methylhexanoids offer insights into carotenoid metabolism.
• Methylhexanoids and cyclofarnesoids may play roles in species-specific fungal physiology and behavior, independent of sexual pheromone activity.