If you are interested by generating quickly a list of compounds that were previously identified in a plant, the online dictionary of natural product is a good place where to start your research. It regroups entries for >270k natural chemical compounds.
In the current version of the website (March 2016) you can search for “Biological source” and in there “the latin name of your favourite species”. The result of such a query for “Helianthus” is a list of 381 chemical compounds that were tagged as identified in Sunflower species (and a minority of other species with helianthus in the name). Of course this list is quite restricted compared to the number of metabolites produced by sunflower plants. It is however a good starting point to know what kind of compounds (here a lot of terpenes, few flavonoids) were previously extracted from your favourite plant species. Some entries are tissue specific, such as large terpenes from pollen. Also interesting, the “biological use” column gives sometimes information on the role of the compound (e.g. antifungal, allelochemical, growth inhibition).
The CAS registry number is probably the most powerful piece of information you can get out of such a search. It’s the unique ID for the compound and can be use to search the compound in multiple databases. My favourite are:
- Chemspider: This is probably the more powerful chemical database that currently exists. It’s huge: it regroups information for more than 44 million chemical structure and cross-reference with many other databases.
- Pubchem: It will look really familiar to NCBI/pubmed users. With pubchem you can for exemple submit the CAS number and get a list of publications linked to the compound.