NMR spectroscopy and antioxidant activity of flavanones and flavones isolated from Chromolaena tacotana (Klatt) R.M. King & H. Rob

Chromolaena tacotana is considered as a source of flavonoids. Here we examined the content and antioxidant properties of flavones and flavanones from the leaves of the plant. Four flavonoids, including (Cta) 5, 4' dihydroxy-7-methoxy flavanone, (Ctb) 3,5,3'-trihydroxy-7,4'-dimethoxyflavone; (Ctc), 3,4'-dihydroxy -5,7-dimethoxyflavanone; and (Ctd) 4'-hydroxy-5,7-dimethoxyflavanone, were isolated from leaves extracts, were identified by their NMR spectroscopic data, and then free radical scavenging activities of the flavonoids were assessed against DPPH. The antioxidant activity for the flavanone Ctb was the highest even compared to that of quercetin, with IC50 of 6.27 μg/mL and 8.67 μg/mL respectively. The flavanones Cta, Ctc and Ctd presented a lowest activity against free radicals as expected according to their molecular substituents and the position within the structure. Data obtained from this study support the ethnomedicinal use of the leaves of C. tacotana for an antioxidant purpose.