I am working with a native medicinal plant and I need a protocol to discover its essential compounds, but I have no idea what kind of compounds I will find.
I think the easiest way is by doing GC MS and LC Ms of the extract of your plant. You can try at first MeOH extract of the plant. BY GC MS and or LC MS you can predict the main compounds of your extract by comparing the exact MW, Molecular Formula, their pattern of the fragmentation to some (on line) MS data base.
Step 1: Check the reported secondary metabolite chemistry of the medicinal plant species in literature
Step 2: Check the reported secondary metabolite chemistry of the related species of the same genus in literature
Step 3: Check the reported secondary metabolite chemistry of the related genera within the same family/subfamily
This chemosystematics approach will give you a broad understanding of the types/groups of chemistry (eg.flavonoids, terpenoids, lignans etc) reported.
Step 4: Do a simple HPTLC separation: you can get the optimal mobile phases for each group of chemistry and specific detection reagents from Wagner's Book on "Plant Drug Analysis - A thin layer chromatography Atlas'. once you get some clue, then
Step 4: Look for general LC-PDA -MS methods for the chemical groups. For example, you will find some excellent reviews on flavonoids. With the combined UV spectral and mass spectral data, you can get a lot of valuable information to identify individual compounds.
If you let me know the plant species, I can provide you more info from literature.
All the best
Try to find out some paper related with phytochemical screening of any medicinal plant. You must get idea how to proceed with your plant. One sample paper herewith attached.
If you don’t have sophisticated equipments for metabolomics analysis of a methanolic extract a simple way is:
Extraction of plant material with ethanol-H2O (7:3), by maceration at 40º during 24 h in a relation plant-solvent 1:6.
Filtrate the suspension and eliminate the ethanol at vacuum and extract the aqueous solution with solvents of increased polarity: CHCl3, AcOEt; BuOH and lyophilizing the aqueous phase.
Each of the fractions obtained can be analyzed using simple methods TLC (with reagents specific for different families of phytochemicals) and further GC-MS (CHCl3-extract); HPLC (CHCl3, AcOEt; BuOH-H2O and extracts): also LC-MS / MS
Here are some interesting publications to guide you through the steps of isolation and identification of chemical compounds from plant extracts:
Here is an interesting link with several presentations and publications:
http://www.slideshare.net/rahulbs89/extraction-of-plant-contituents
Phytochemical Methods: A Guide to Modern Techniques of Plant Analysis; Jeffrey B. Harborne; ISBN-13: 978-0412230509
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