it is the tests that done to evaluate the antioxidants capacity of natural compounds in plants. those natural compounds mainly are polyphenols like phenolic acids, flavonoids , carotenoids and tochepherols among others. 

those tests examine the effects of antioxidants in controlling the extent of oxidation process .

many examples of those tests like: ABTS test, DPPH test, iron chelating activity , beta-carotene bleaching activity, hydroxyl radical scavenging activity and many others

Dear Kaushi

Here are some publications on the antioxidant activity and some of the threads on antioxidant activity.

https://www.researchgate.net/post/What_are_the_techniques_used_to_check_the_antioxidant_potential_of_an_isolated_compound

https://www.researchgate.net/post/How_can_we_check_the_effects_of_antioxidant_on_tissue

https://www.researchgate.net/post/which_compound_whether_natural_or_synthetic_is_consider_as_a_super-antioxidant

https://www.researchgate.net/post/which_plant_is_commonly_used_as_a_source_of_natural_antioxidants_in_traditional_medicine

https://www.researchgate.net/post/How_we_can_measure_free_radical_scavenger_activity_of_a_plant_extract

https://www.researchgate.net/post/How_can_I_calculate_antioxidant_activity_for_plants?tpr_view=8dbf4a0d-f474-4ae8-9afd-0927626f6b52_1

Thank you for your kind cooperation on answering and help me. actually I want to find some background review on Antioxidant assays, total phenolic content, total flavonoid and alpha amylase enzyme assay of plant Aporosa lindleyana. And want to know about any kind of previous researches carried out on that plant Aporosa lindleyana. If you have some pls send me the links. Thanks.