Dear Harleen 

 please see the attached link 

Regards 

Saif

http://www.cancer.org/treatment/treatmentsandsideeffects/complementaryandalternativemedicine/dietarysupplements/dietary-supplements-manufacturing-guidelines

Dear Saifeldin,

Thanks for your response. I have gone through the provided link but I still haven't found the desired information regarding addition of Vitamins and Antioxidants with herbs. I need certain stepwise methodology for the same and how to handle individual vitamins and antioxidants as some are hydrophilic while others may be lipophilic.

Extraction consists of 2 parts which are hydrophilic and lipophilic parts.Depend on the nature of your herbs. Normally it  contains both. After extraction you can use any method to quantify the non-volatile and volatile content as HPLC ,Gas Chromatography,Spectrometer, and DPPH, ABTS, ect.