Fig. 4.

Bioactivity-guided HPLC purification and NMR analyses led to the isolation and identification of rutin and nicotiflorin. The purification of P. insularum homogenate was tracked using a bioassay-guided approach in tandem with NMR analyses. (A) The HPLC chromatogram, monitored at 254 nm, showing the two peaks (boxed) that exhibited bioactivity. (B) Percent growth of WT yeast in increasing concentrations of HPLC fraction 1 or 2 with the absence or addition of 100 µM FeCl₃ compared to growth in media without each fraction. (C) The ¹H NMR (600 MHz, CD₃OD) spectrum of each fraction was subsequently identified as (D) rutin and nicotiflorin.