Use if you can MTS assay kit that is a version with all-in-one incorporated reagents. For your plant extracts use as many controls if you can as it is known that MTT-type assays can be influenced by the merely plant extract components. So, to be on the safe part, be sure that your extracts are not influencing your MTT readings per se.
Hello Sandeep....MTT assay facility is available in ACTREC, TMC, Mumbai. You can do your analysis there and another place is IVRI, Izatnagar Bareli, Uttar Pradesh. Dr. B C SARAVANAN, Senior Scientist in Parasitology Division, You can talk to him, His contact details are below: