Seasonal variations in the phenolic compounds and antioxidant activity of Pyrrosia petiolosa (Christ et bar.) Ching

Pyrrosia petiolosa (Christ et Bar.) Ching is an evergreen fern, its dried leaves serving as one of the sources of the traditional Chinese medicine "Shiwei", which can be used to treat acute pyelonephritis, chronic bronchitis, and bronchial asthma. In this study, the leaves of this plant were harvested from January to December, and ethanol extracts of trophophylls (EET) and sporophylls (EES), and hot water extracts of trophophylls (HET) and sporophylls (HES) were prepared. Extracts were evaluated for seasonal changes in the contents of chlorogenic acid (CGA), neochlorogenic acid (NCGA), total phenols (TP), and total flavonoids (TF), as well as their antioxidant activity. The results showed that from spring to winter, the levels of CGA, NCGA, TF, and TP in the leaves of P. petiolosa exhibited an overall trend of first decreasing and then increasing, although the degree of change varied. In the spring and summer months, specifically from March to June, the leaves contain rich phenolic compounds and had high antioxidant activities. Moreover, the ethanol extracts from the leaves collected in spring exhibit the best antioxidant activity. Overall, it is suggested that spring is the optimal harvesting season for P.petiolsa, followed by summer.