Researchers have discovered that Daphne pseudomezereum (commonly known as Onishibari) contains a substance inhibiting replication of human immunodeficiency virus (HIV). The plants were cultivated at the Medicinal Plant Garden of the Faculty of Pharmaceutical Sciences, Toho University. This finding is expected to lead to the discovery of drug seeds for novel drugs with superior anti-HIV activity.

A paper reporting this study was published in the journal Phytochemistry. The research group was led by Professor Wei Li from the Department of Pharmacognosy, Faculty of Pharmaceutical Sciences, Toho University, in collaboration with the Duke University Medical Center in the United States.

The Thymelaeaceae family consists of over 53 genera and 800 species distributed worldwide, except in polar and desert regions. These plants contain diterpenoids, which exhibit significant biological activities, including anticancer, anti-HIV, and analgesic effects.

D. pseudomezereum is a deciduous shrub of the Thymelaeaceae family found in Japan, China, and Korea. Its bark has been traditionally used in medicine to treat chronic skin diseases and rheumatism due to its anti-inflammatory properties. Additionally, this fiber-rich bark has been utilized as an additive in Japanese paper production.

In the study, a research group isolated 10 daphnane diterpenoids, including three previously undescribed compounds, from the fruits of D. pseudomezereum. Among the isolated compounds, three exhibited potent anti-HIV activity, with EC₅₀ values around 1 nM and cytotoxicity at IC50 > 5 μM.

The findings of this study not only underscore the promising anti-HIV potential of daphnane diterpenoids but also provide a foundation for future research aimed at optimizing their activity through strategic structural modifications.