Whether it is herbs or single compounds the methodology interpretation and representation is same. The only factor to be important here is that you should have appropriate positive (known antibiotics) and negative (placebo) controls included
Agreeing with Shrinath Baliga, I think the attached literate will help. You can also see the CLSI protocol for MIC determinations, they have series of protocol for conducting antimicrobial susceptibility. In all cases, MIC is usually reported in μg/mL.