Simplex Optimized LC Analysis of Plant Coumarins and Furanocoumarins

Sequential simplex methods are common and efficient optimization techniques applied in analytical chemistry. This study reports on the optimization of LC separation of coumarins using a variable-size simplex algorithm. The solvent systems consisted of methanol, water and tetrahydrofuran. Using an optimized method, seven standard simple coumarins and furanocoumarins derived from plants were successfully separated in one chromatographic run. The mobile phase at the point corresponding to the optimum consisted of 34% MeOH, 59% H₂O and 7% THF. Applying a solvent mixture in this proportion permitted separation of all critical pairs, such as esculetin/scopoletin, scopoletin/umbelliferone, umbelliferone/coumarin and xanthotoxin/psoralen. The retention ratio factors k for coumarins at the optimum of the simplex algorithm lay in the range 1 < k < 4. The optimal conditions assigned to the coumarin standards were then applied to the plant matter: herb of the rue (Ruta graveolens L., Rutae herba), anthodium of the camomile (Chamomilla recutita L., Chamomillae anthodium), herb of the southernwood (Artemisia abrotanum L., Abrotani herba), and radix of the lovage (Levisticum officinale K., Levistici radix). The validity of the method was confirmed with respect to these samples.