Quantitative determination of secondary metabolites in Cladina stellaris and other lichens by micellar electrokinetic chromatography

The quantitative determination of usnic acid (UA), perlatolic acid (PA), and atranorin (AT) in Alaska lichens by micellar electrokinetic chromatography (MEKC) is reported. The background electrolyte (BGE) included sodium docecyl sulfate (SDS), and β-cyclodextrin (β-CD) in a high-pH borate buffer. The presence of β-CD in the buffer significantly decreases peak width, especially for UA, as it decreases migration time for both UA and PA. Linear calibration curves for UA, PA, and AT were established using an internal standard of benzoic acid (BA). Concentration limits of detection (cLODs) are 2.5, 2.2 and 2.0 μg/mL (S/N 3) for UA, PA, and AT, respectively. Dry samples of lichen were extracted at room temperature with acetone for 24 h in the presence of BA as internal standard. Recoveries of UA from spiked samples ranged from 92 to 98%. Amounts of UA and PA in the lichen samples ranged from 0.28 to 1.7% dry weight and 0.02 to 0.23%, respectively.