Coleus forskholii, a tropical member of the Mint family, has been used in Ayurveda for thousands of years. Recent research points to its role in increasing levels of intracellular cAMP (cyclic adenosine mono-phosphate), a secondary messenger involved in a variety of biochemical processes. Increasing levels of cAMP has numerous, system-wide effects that mostly relate to "yin"-like changes: reduced inflammation, blood pressure, anxiety, irritability; and increased activation of GABA neurons (here is a useful summary of the research and biochemistry of Coleus).
Now, in a study that is receiving lots of media attention, scientists have found that Coleus extracts are useful in chronic urinary tract infections (UTIs) by reducing the adherence and number of bacterial colonies that hide in the folds of the bladder. Coupled with antibiotics, the study reports, these extracts lead to a more complete and long-lasting remission from UTIs.
Some problems with this research: first, it was done on an animal model (mice). And while cells lining the inside of the mouse bladders did "kick out" bacteria when exposed to Coleus, the plant extract was injected directly into the bladder and bladder tissue. This method is not too practical for us herbalists, and the study reveals nothing about the pharmacodynamics of orally-administered Coleus. So, interesting information. But despite the media attention, not incredibly useful... Hopefully this will spur additional research.