Sesquiterpene lactones and other constituents from Hedyosmum brasiliense

Hedyosmum brasiliense Miq. is an endemic, aromatic arborescent shrub, which is the only representative of Chlorantaceae in Brazil. There have been few studies that seek to determine its chemical composition and/or pharmacological effects. This work describes five new compounds: two guaianolides, two elemanolides and a dimeric lindenanolide, which were tested against Mycobacterium tuberculosis, together with some widespread phenolics. All the structures of the isolated compounds were elucidated based on extensive analysis of 1D and 2D NMR and MS data, and also in comparison with the published data. The new compounds found were: 1,2-epoxy-10α-hydroxy-podoandin (3), 1-hydroxy-10,15-methylenepodoandin (4), 15-acetyl-isogermafurenolide (5), 15-hydroxy-isogermafurenolide (6) and brasiliensolide (7) – which is the first dimeric sesquiterpenolide identified in the Hedyosmum genus. The phenolic compounds isolated were scopoletin, vanillin, vanillic acid, protocatechuic aldehyde and ethyl caffeate. The isolated sesquiterpene lactones, at concentrations in the range of 1–30µM, did not show in vitro anti-mycobacterial activity, since M. tuberculosis cultures exposed to the Hedyosmum brasiliense-derived substances kept growing but were sensitive to isoniazid, an antibacterial agent.

Figure 1: Isolated compounds of Hedyosmum brasiliense

Figure 2: Key NOE correlations observed for compounds 4 and 5

Acknowledgement: The authors are grateful to CNPq and CAPES for financial support, and Norberto P. Lopes and José C. Tomaz (FCFRP-USP) and Luciano F. Huergo (Departamento de Bioquimica e Biologia Molecular-UFPR) for the MS analysis and André Báfica (Laboratório de Imunofarmacologia e Doenças Infecciosas-UFSC) for the antimicrobial assay.