Complete 1H and 13C NMR assignments and antifungal activity of two 8-hydroxy flavonoids in mixture

A mixture of the two new flavonols 8-hydroxy-3,4',5,6,7-pentamethoxyflavone (1) and 8-hydroxy-3,3',4' 5,6,7-hexamethoxyflavone (2) was isolated from a commercial sample of Citrus aurantifolia. An array of one- ((HNMR)-H-1, {H-1}-C-13 NMR, and APT-C-13 NMR) and two-dimensional NMR techniques (COSY, NOESY, HMQC and HMBC) was used to achieve the structural elucidation and the complete H-1 and C-13 chemical shift assignments of these natural compounds. In addition, the antifungal activity of these compounds against phytopathogenic and human pathogenic fungi was investigated.