???
What type of spectrograms?
You’re unlikely to find anything useful and publicly available other than TLC pics. You’ll find spectroscopic data and a lot more on natural products
HERE but it’s going to cost you a few pennies (it’s THE reference work and a must have if you’re doing research with herbal constituents).
Spectroscopic analyses are done on whole plant extracts but more often to identify new constituents or quantify certain constituents (in order to standardise said extract) rather than to confirm identity and these are also seldom published, let alone in a complete work. You’ll have to dig through pubmed and sciencedirect.
The problem is, plants aren’t a defined compound and extracts are different between growing sites, seasons, varieties, soil type etc. etc.
What are you trying to do?