Analytical characterization of lichexanthone in lichen: HPLC, UV spectroscopic, and DFT analysis of lichexanthone extracted from Laurera benguelensis (Mull. Arg.) Zahlbr.

Abstract

Lichexanthone, the major pigment present in the extract of Laurera benguelensis (Mull. Arg.) Zahlbr., was extracted from lichen, purified, and characterized by high-performance liquid chromatography (HPLC) and ultraviolet (UV) spectroscopy. The geometry of the lichexanthone conformers was optimized at the B3LYP/6-31+G** level of theory. It was found that all conformations have similar energies and that the corresponding lichexanthone radical is planar. In spite of its planarity, there is no significant electron delocalization over the radical. The antioxidant properties of lichexanthone were investigated using the colorimetric assay as Trolox-equivalent antioxidant capacity and at B3LYP/6-31+G** level of theory. Both methods revealed that lichexanthone has weak antioxidant properties. The results confirm the potential of HPLC-UV analysis for taxonomic characterization of lichen species. © Springer-Verlag 2010.