Dear Khaled 

If you provide details about the plant species and the phytochemicals you want to anlyse, RG friends can help you since protocols differ based on the phytochemicals to be analysed. When we worked on pyrethrum (Chrysanthemum/Tenacetum cinerariaefolium), an insecticidal plant introduced into India, we employed an UV spectrophotometric method to analyse the pyrethrins (natural insecticides) content of the flowers.

Best wishes

Dear Rajeswara

Tribulus sp. and I want analyse an alkaloids and tannins

thank you

Dear Khaled

The easiest way is to follow the threads on alkaloid and tannins analysis in RG. Several other RG members have asked similar questions on isolation methods for diverse secondary metabolites and experts have provided diverse answers. 

Check the following threads for possible leads:

Good luck.

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

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

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

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

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

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

https://www.researchgate.net/post/Does_simple_partitioning_with_acidic_water_convert_alkaloid_salts_from_its_free_base_which_is_oily_in_nature2

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

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

https://www.researchgate.net/post/Which_do_you_recommend_fresh_or_semi-dry_or_dry_biomass_tissue_for_an_aqueous_solvent_extract_or_for_extracting_isolating_separating_phytochemicals

Dear Khaled

I am attaching some pdf files on the subject of spectrophotometric analysis and a word file providing links to papers on the subject. I have downloaded the information and procedures after searching Google Scholar. You may search for more articles on the subject.

Good luck.

Dear Khaled

Check this publication.

thank you Dear Dr. Rajeswara Rao