An essential oil-free infusion of lemongrass was prepared and
fractionated by column chromatography as previously described
(Figueirinha et al., 2008). All the fractionation process
was monitored by high-performance liquid chromatography
(HPLC) and thin layer chromatography (TLC) for polyphenols.
The flavonoid-rich fraction was used as the starting point to
isolate luteolin 7-O-β-glucopyranoside, luteolin 6-C-β-
glucopyranoside and luteolin 2″-O-rhamnosyl-C-(6-deoxy-ribohexos-
3-ulosyl), commonly known as cassiaoccidentalin B.
Freeze-dried flavonoid-rich fraction was dissolved in methanol
and applied on chromatography cellulose paper sheets
(46 × 57 cm) Whatman® 3MM (Maldstone, England), and eluted
in a saturated chamber with 15% acetic acid. Each isolated spot
was detected by UV (366 nm) observation and removed from
the paper by 50% methanol extraction and purified on polyamide.
Structural elucidation of each isolated flavonoid was
achieved by 1H NMR.