Fig. 4: Checkerboard assay representing synergistic effect between potential hits and standard drug vancomycin.

A–H Heat maps of checkerboard assay between synthesized trisindoline derivatives and vancomycin. Synergistic combinations of compounds 3b, 3c, 3d, 3e, 3g, 3l, 3n and 3o with vancomycin, respectively. (Where % Inh represents percentage of inhibition, the orange color elucidates the inhibitory effect and the pale-yellow color displays visible growth of MRSA). A green dot in the heat map represented the best FIC value with FIC index <0.5, for each compound synergizes with standard antibiotic vancomycin.