Anti-Influenza Virus Activity and Constituents. Characterization of Paeonia delavayi Extracts.

Paeonia delavayi, an endemic species in southwestern China, has been widely used as a traditional remedy for cardiovascular, extravasated blood, stagnated blood and female diseases in traditional Chinese medicine (TCM). However, there are no reports on the anti-influenza virus activity of this species. Here, the anti-influenza virus activity of P. delavayi root extracts was first evaluated by an influenza virus neuraminidase (NA) inhibition assay. Meantime, constituents in the active extracts were identified using ultra-high performance liquid coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) and seven major identified constituents were used to further evaluate the NA inhibitory activity. The results showed that the ethyl acetate fraction (EA) and the ethanol fraction (E) of P. delavayi both presented strong NA inhibitory activity with IC50 values of 75.932 μg/mL and 83.550 μg/mL, respectively. Twenty-seven constituents were characterized in these two active extracts by UPLC-Q-TOF-MS analysis, and seven major identified constituents exhibited high activity against the influenza virus. Among them, Benzoylpaeoniflorin (IC50 = 143.701 µM) and pentagalloylglucose (IC50 = 62.671 µM) exhibited the highest activity against the influenza virus, even far stronger than oseltamivir acid (IC50 = 281.308 µM). This study indicated that P. delavayi was a strong NA inhibitor, but cell-based inhibition, anti-influenza virus activity in vivo and anti-influenza virus mechanism still need to be tested and explored.