Comparison of the Antifungal Activity of Cadinane Skeletal Sesquiterpenoids from Taiwania (Taiwania cryptomerioides Hayata) Heartwood

Summary The antifungal activity of cadinane skeletal sesquiterpenoids from Taiwania (Taiwania cryptomerioides Hayata) heartwood is demonstrated. Using spectral analyses, the absolute structures of three main cadinanes, T-cadinol, T-muurolol, and α-cadinol, all isolated from Taiwania with HPLC, were identified. The amount of these cadinanes was also quantified using GC. The results showed that the total amount of cadinanes extracted from heartwood with n-C6H14 was 6.49 mg per kg of wood. This was much more than the essential oils collected by water distillation from leaves (0.04 mg/kg), sapwood (0.36 mg/kg), or heartwood (1.77 mg/kg). Moreover, results obtained from the antifungal assays demonstrated that αcadinol exhibited the highest antifungal index for both Coriolus versicolor and Laetiporus sulphureus, followed by T-cadinol and T-muurolol. As a matter of fact, α-cadinol completely inhibited the growth of C. versicolor and L. sulphureus at the level as low as 100 ppm. Further comparison of the molecular configuration of these cadinanes reveals that cadinane skeletal sesquiterpenoids with an equatorial hydroxyl group at C-9 and a trans configuration at the ring junction, such as the case for α-cadinol, exhibited the strongest antifungal activity.