Nicotabin A, a Sesquiterpenoid Derivative from Nicotiana tabacum.

Nicotabin A (1), a sesquiterpenoid derivative possessing a fused 5/6/5/5/5 ring system, was isolated from leaves of Nicotiana tabacum. The structure was elucidated by extensive spectroscopic methods and confirmed by single crystal X-ray diffraction. The plausible biosynthetic pathway for 1 was proposed. Compound 1 inhibited nitric oxide production in LPS-activated RAW264.7 macrophages with an IC50 of 22.1 μM.