Scutellaria barbata is a plant used in traditional Chinese medicine. Other names include ban zhi lian, scullcap or skullcap, barbat skullcap, skute barbata, or herba scutellariae barbatae. Scutellaria barbata is used in some traditional herbal sleeping remedies and for anxiety, migraines, and depression. Bionovo is testing its use as a treatment for advanced breast cancer and pancreatic cancer. Three new neo-clerodane diterpenoids, named scutelinquanines A–C (1–3), were isolated from the whole plant of Scutellaria barbata. Their structures were established on the basis of detailed spectroscopic analyses. In vitro, the isolated three new compounds showed significant cytotoxic activities against three human cancer lines (HONE-1 nasopharyngeal, KB oral epidermoid carcinoma, and HT29 colorectal carcinoma cells), and gave IC50 values in the range 2.7–6.7 μM.