Swarnalin and cis-swarnalin, two new tetrahydrofuran derivatives with free radical scavenging activity, from the aerial parts of Cuscuta reflexa

Abstract

The reversed-phase HPLC analysis of a methanol extract of the aerial parts of Cuscuta reflexa afforded a non-separable mixture (55 : 45) of two novel tetrahydrofuran derivatives, named swarnalin (1) and cis-swarnalin (2), and a known coumarin, 5,6,7-trimethoxycoumarin (3). The structures of the compounds were elucidated unequivocally by UV, HRFABMS and a series of 1D and 2D NMR analyses. The mixture of 1 and 2 showed significant free radical scavenging activity in the DPPH assay and the RC₅₀ value was found to be 3.80 × 10⁻⁴ mg mL⁻¹ for the mixture, compared to 2.88 × 10⁻⁵ mg mL⁻¹ for the positive control, quercetin.

Keywords:

• Cuscuta reflexa
• Convolvulaceae
• Tetrahydrofuran
• Coumarin
• DPPH assay
• Swarnalin
• cis-Swarnalin
• NMR

Acknowledgement

We thank EPSRC National Mass Spectrometry Service Centre (Department of Chemistry, University of Wales Swansea, Swansea, Wales, UK) for MS analyses.