Antimycobacterial and Nitric Oxide Production Inhibitory Activities of Goyazensolide and Centratherin Isolated From <i>Eremanthus crotonoides</i> by High‐Speed Countercurrent Chromatography

In this study, bioassay-guided fractionation of the ethanolic extract from Eremanthus crotonoides leaves enabled the isolation of two bioactive sesquiterpene lactones, centratherin and goyazensolide, which were evaluated for their antimycobacterial and anti-inflammatory properties. The extract exhibited MIC₅₀ values of 42.0 ± 0.1 and 39.0 ± 0.1 µg/mL against Mycobacterium tuberculosis H₃₇Rv and the hypervirulent M299 strain, respectively, along with notable NO inhibitory activity. Fractionation by high-speed countercurrent chromatography (HSCCC), followed by purification also employing HSCCC, yielded centratherin and goyazensolide, representing the first report of their isolation from E. crotonoides using this technique. These compounds showed potent activity against H₃₇Rv (MIC₅₀ = 1.5 ± 0.1 and 2.5 ± 0.1 µg/mL, respectively) but markedly reduced activity against M299 (MIC₅₀ = 92.7 ± 0.1 and 90.6 ± 0.1 µg/mL). Both compounds also exhibited IC₅₀ values of 0.45 ± 0.1 and 0.34 ± 0.1 µg/mL for nitric oxide inhibition, with low cytotoxicity. Collectively, these findings provide the first evidence of the antimycobacterial potential of these compounds against virulent M. tuberculosis strains and underscore their promise as potential drug candidates.