Floral Trifolium proanthocyanidins: polyphenol formation and compositional diversity

Area of Science:

• Plant biochemistry
• Molecular biology
• Agricultural science

Background:

• Proanthocyanidin biosynthesis involves flavan-3-ols but polymerization enzymes are unknown.
• Previous studies utilized model plants and crops like grape and tobacco.
• Floral proanthocyanidins in Trifolium species offer potential insights into biosynthesis.

Purpose of the Study:

• To investigate floral proanthocyanidins in 10 Trifolium species.
• To identify Trifolium species with contrasting proanthocyanidin chemistry.
• To find factors involved in proanthocyanidin polymerization.

Main Methods:

• Analysis of floral proanthocyanidins from 10 Trifolium species.
• Thiolyic cleavage to liberate flavan-3-ol extension units.
• MALDI-TOF MS to determine oligomer compositional dispersion.

Main Results:

• Proanthocyanidins were found in Trifolium floral portions (3.1-12.2 g/100 g dry matter).
• Extension units were predominantly cis-stereochemistry.
• Terminal unit stereochemistry varied: T. michelianum (trans), T. hirtum (mixed trans), T. vesiculosum (cis/trans).
• MALDI-TOF MS revealed oligomers up to approximately 2200 Da.

Conclusions:

• Floral proanthocyanidins are present in Trifolium species.
• Stereochemistry of terminal units differs among species.
• T. michelianum, T. hirtum, and T. vesiculosum warrant further investigation for proanthocyanidin biosynthesis insights.