A simple and accurate reversed phase HPLC procedure is proposed for the determination of 19 phenolic compounds (flavonoids, phenolic acids, and coumarins) in seven medicinal species. The sample preparation involved extraction, alkaline and acid hydrolysis, and purification through a Bond-Elut C18 column. The chromatographic separation was achieved using a reversed phase column Spherisorb ODS2 (5μm; 25.0 × 0.46 cm). Gradient elution was carried out using water-formic acid (19:1) (A) and methanol (B). A diode-array detector monitored the effluent and chromatograms were recorded at 280, 320, and 350 nm. The optimised methodology seems to be useful for the phytochemical analysis of plant extracts. A close correlation between the phenolic compound patterns and the botanical origin of plants was found.