I'm using PNG Express to extract asset from Photoshop. Is there any supporting plugin for Adobe illustrator to extract the assets?
I don't use any extra plugins to export .pngs in Illustrator. I've found that using a single large artboard and creating named slices work well to export multiple .pngs. Simply create the slices you want and then use File > Save for Web and either leave All slices selected or choose the slices you want.
I then optimise the exported files for the best performance using ImageOptim on Mac or FileOptimizer on Windows.
Illustrator works nicely for mobile design as it can produce scalable .svgs, saving a lot of hassle working with various high dpi screens.
Illustrator has an "Unembed" feature that will extract a source image in its original resolution as either a PSD or Tiff. "Unembed" appears in the control panel when the image is selected, or from the Links pallet flyout menu. You can then batch convert the images to PNG if you like.