Tripterygium regelii

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Tripterygium regelii, commonly called Regel's threewingnut, is a shrubby, deciduous vine native to Korea, Japan, and Manchuria. It grows to about 2 meters tall. From May to June it bears small yellowish‑white flowers on long branched clusters and has a light scent similar to freshly cut hay. The fruits are greenish-white, three‑angled, and winged.

Taxonomy and relation to other species: It belongs to the genus Tripterygium in the Celastraceae family. Studies support recognizing T. regelii as a separate species from the better‑known Leigongteng (T. wilfordii). Some plants once thought to be different species are now considered the same as T. wilfordii or T. regelii. DNA data can help detect adulterants in commercial herbal products.

Toxicity and uses: Tripterygium species are listed as poisonous by the U.S. FDA. Some extracts have produced temporary antifertility effects in studies, which has driven research into potential contraception.

Chemistry: Compounds called hypoglaunines can be isolated from the bark of T. regelii. Hypoglaunine B is a macrolide‑like alkaloid with a substituted pyridine and dihydroagarofuran structure and has shown anti‑HIV activity in laboratory tests.