Four new isocoumarins from Cajanus cajan

Area of Science:

• Natural Products Chemistry
• Phytochemistry
• Organic Chemistry

Background:

• Cajanus cajan (pigeon pea) is a widely cultivated legume with a rich history of traditional medicinal uses.
• Isocoumarins are a class of natural products with diverse biological activities, but their biosynthesis in plants remains incompletely understood.

Purpose of the Study:

• To isolate and characterize novel isocoumarins from Cajanus cajan.
• To investigate the stereochemistry and propose a biosynthetic pathway for the isolated compounds.

Main Methods:

• Extraction of Cajanus cajan leaves using ethanol.
• Extensive spectroscopic analysis including UV, IR, NMR (1D and 2D), and High-Resolution Electrospray Ionization Mass Spectrometry (HRESIMS).
• Chiral analysis to determine the stereochemistry of the isolated compounds.

Main Results:

• Isolation of four new isocoumarins: cajanolactone B, C, D1, and D2.
• Complete structural elucidation of compounds 1-4 using comprehensive spectroscopic data.
• Determination that all isolated isocoumarins exist in racemic forms.
• Identification of compounds 3 and 4 sharing the same planar structure.

Conclusions:

• The discovery of novel racemic isocoumarins from Cajanus cajan expands the known chemical diversity of this plant genus.
• The racemic nature of the isolated compounds suggests that the biosynthesis of isocoumarins in C. cajan is tolerant to chirality.
• A proposed biogenetic pathway provides insights into the formation of these novel isocoumarins within the plant.