Q:

General Alkaloid Extraction Process

I'm getting into alkaloid extraction from various ethnobotanicals. It is a bit frustrating trying to extract alkaloids from ethnobotanicals without good guides out there, and I wanted to make my own techniques and experiments. However, I need to know what the basic outline is for extraction. Are there any guides or basic principles I need to know? 
I'm interested in extracting for example Leonurine from Wild Dagga or Mitragyna and 7-OH-Mitragyna from Kratom.

What I was looking for was Acid-Base or Liquid-Liquid extractions.

A:

7-Hydroxymitragynine
The extraction and crystallization of the parent alkaloid, mitragynine, from dried leaves of Mitragyna speciosa (Kratom), has been described in great detail by A. H. Beckett, E. J. Shellard and A. N. Tackie in Planta Med., 1965, 13, 241-246 (DOI).
(Interestingly, the procedure also furnished speciofoline, a spiroindolo indolizidine alkaloid.)
Leonurine
A first extraction was seeming reported by S. Kubota and S. Nakajima in Nippon Yakubutsuqaku Zasshi, 1930, 153. I don't have a DOI and the source is most likely in Japanese.
I don't have personal experience with the extraction of guanidines from biological material and would probably rather try to synthesize leonurine, following the procedures described in Tetrahedron, 1969, 25, 5155-5161 (DOI).

General guidelines
I have given some hints on extraction in an answer to a question on the use of TLC in alkaloid identification.

