Recent progress in the antiviral activity and mechanism study of pentacyclic triterpenoids and their derivatives.

Viral infections cause many serious human diseases with high mortality rates. New drug-resistant strains are continually emerging due to the high viral mutation rate, which makes it necessary to develop new antiviral agents. Compounds of plant origin are particularly interesting. The pentacyclic triterpenoids (PTs) are a diverse class of natural products from plants composed of three terpene units. They exhibit antitumor, anti-inflammatory, and antiviral activities. Oleanolic, betulinic, and ursolic acids are representative PTs widely present in nature with a broad antiviral spectrum. This review focuses on the recent literatures in the antiviral efficacy of this class of phytochemicals and their derivatives. In addition, their modes of action are also summarized.