Isoflavonoids isolated from Cuban propolis

Area of Science:

• Natural Product Chemistry
• Phytochemistry
• Analytical Chemistry

Background:

• Propolis, a resinous mixture produced by bees, is known for its diverse biological activities.
• The chemical composition of propolis varies greatly depending on geographical origin and botanical sources.
• Isoflavonoids are a class of flavonoids with potential health benefits, but their presence in propolis has not been previously reported.

Purpose of the Study:

• To conduct a detailed chemical investigation of a red-type Cuban propolis sample.
• To isolate and structurally elucidate the compounds present in the propolis extract.
• To explore the fragmentation patterns of pterocarpans using mass spectrometry for improved identification.

Main Methods:

• Spectroscopic analysis, including Circular Dichroism (CD) and 2D Nuclear Magnetic Resonance (2D NMR) techniques, for structural determination and stereochemistry assignment.
• Electrospray ionization (ESI) tandem mass spectrometry (MS/MS) with an ion-trap analyzer to study pterocarpan fragmentation.
• Isolation and purification of compounds from the propolis extract.

Main Results:

• Isolation of 11 isoflavonoids (2 isoflavones, 3 isoflavans, 6 pterocarpans), along with gallic acid, isoliquiritigenin, and (-)-liquiritigenin.
• Complete structural determination, including absolute stereochemistry, for the isolated compounds.
• Proposal of a generalized fragmentation pathway for pterocarpans based on MS/MS analysis, aiding in their identification.

Conclusions:

• This study reports for the first time the presence of isoflavonoids in propolis.
• The identified compounds represent a novel chemical profile for Cuban propolis.
• The proposed mass spectrometry fragmentation pathway offers a valuable tool for the characterization of pterocarpans in natural products.