Isolation, Chemical Transformation, and Antifungal Potential of Sesquiterpene Lactones from Inula Racemosa

The present study reports the isolation of two eudesmanolide type sesquiterpenoid lactones, viz. alantolactone and isoalantolactone, from the roots of Inula racemosa Hook L. and their chemical transformations using various reagents. All the compounds isolated and synthesized were assessed for their in vitro antifungal potential against Dreschlera oryzae, Fusarium moniliforme, and Alternaria triticina using spore germination inhibition method. To understand how the structure of sesquiterpene lactones relates to their antifungal function, structure activity relationships were studied. Isoalantolactone and its derivatives were found to be more toxic as compared to alantolactone and its derivatives. Among the different synthesized compounds, the bromoform derivatives were the most, while the methoxy derivatives were the least effective. All the compounds showed promising results against three test fungi with ED50 values less than 400 ppm.