Three New Norsesquiterpenoids from the Twigs and Leaves of Nanhaia speciosa

Phytochemical investigation of the 95% ethanol extract from the twigs and leaves of Nanhaia speciosa (Champ. ex Benth.) J. Compton & Schrire led to the isolation of twelve terpenoids. They consist of three new norsesquiterpenoids (1–3), six known norsesquiterpenoids (4–9), two known sesquiterpenoids (10–11), and one known monoterpenoid (12). The structures of the previously undescribed compounds were elucidated by analysis of spectroscopic data and quantum chemical calculations. Notably, compound 2 features an oxidative cleavage between C-5 and C-6 of the six-membered ring, yielding a highly rare seco-norsesquiterpenoid skeleton. Furthermore, compound 10 exhibited moderate antiproliferative activity against A549 cells (IC50 = 13.7 ± 1.8 μM). This study significantly enriches the chemical profile of the aerial parts of N. speciosa.