Cyclooxygenase enzyme inhibitory compounds with antioxidant activities from Piper methysticum (kava kava) roots

Cyclooxygenase enzyme inhibitory assay-guided purification of ethyl acetate extract of Piper methysticum (kava kava) roots yielded six biologically active compounds (1-7), which were purified using MPLC, preparative TLC and HPLC methods. These compounds were also evaluated for antioxidant activities. Dihydrokawain (1) and yangonin (6) showed the highest COX-I and COX-II inhibitory activities at 100 mug/ml, respectively. The lipid oxidation assay did not reveal antioxidant activities for demethoxyangonin (2), dihydrokawain (1), kawain (4), dihydromethysticin (5) or methysticin (7) at 50 mug/ml. The antioxidant activities of flavokawain A (3) and yangonin (6) could not be tested in the lipid oxidation assay due to solubility problems. However, yangonin and methysticin showed moderate antioxidant activities in the free radical scavenging assay at 2.5 mg/ml.