A new dihydroagarofuranoid sesquiterpene from Microtropis fokienensis with antituberculosis activity

A new dihydroagarofuran-based sesquiterpene, 8-acetoxymutangin (1), was isolated from the stems of Microtropis fokienensis, together with eight known compounds, including mutangin (2). Their structures were determined through in-depth spectroscopic and mass-spectrometric analyses. Among the isolated compounds, 1 exhibited potent in vitro antituberculosis activity, with an MIC value of 10.0 microg/ml against Mycobacterium tuberculosis 90-221387, which is considerably better than that of mutangin (2). The activity of 1 lies in the same range as that of the clinic drug ethambutol (MIC 6.25 microg/ml), despite completely different chemical structures, which indicates different modes of action.