Fig. 4
a Chromatogram of 7 available polyphenol and flavonoid standards monitored at 280 nm and identified by retention time (minutes) 1: catechin, 2: vanillic acid, 3: cafeic acid, 4: syringic acid, 5: rutin, 6: ferulic acid, 7: vanillin. b HPLC chromatogram of A.S. extract obtained under optimum conditions: 88 % water and 12 % acetonitril, 50 min. Peak no. 1: catechin, 2: vanillic acid and 6: ferulic acid were identified. c The chemical structure of the three identified compounds