Changes in antioxidant activity and marker compounds in ethanolic extracts of butterbur (Petasites japonicus) depending on harvest time

This study investigated the content of marker compounds, antioxidant components, and antioxidant activities of butterbur (Petasites japonicus) extracts depending on harvest time. The marker compounds protocatechuic acid, caffeic acid, 3,5-dicaffeoylquinic acid, and bakkenolide B were found to be most abundant in extracts obtained in July using 70% ethanol, with concentrations of 0.85, 1.89, 4.37, and 15.13 mg/g, respectively. Conversely, the content of these marker compounds in the extracts obtained with 95% ethanol was lower than that of the 70% ethanol extracts. In addition, the total polyphenol and total flavonoid contents were highest in the July extracts obtained with 70% ethanol, measuring 41.91 μg/mg and 23.73 μg/mg, respectively. The antioxidant activity revealed that the DPPH radical scavenging activity was highest in the May extracts obtained with 70% ethanol, exhibiting a value of 74.76% at a concentration of 5 mg/mL. In contrast, the ABTS radical scavenging activity was highest in the July extracts obtained with 70% ethanol, at 33.48% at the same concentration. These findings suggest that the extraction of butterbur harvested in July with 70% ethanol is the most effective condition for producing high-functional extracts.