https://www.mdpi.com/2072-6643/18/3/376
Functional Phytochemicals Cooperatively Suppress Inflammation in RAW264.7 Cells
RAW 264.7 cells are a mouse macrophage cell line commonly used in research to study immune responses, inflammation, and cancer.
What does this mean?
Meaning everything is a mess to try and disentangle.
Bacteria can stash intermediate pathway results outside of their cell wall for various reasons (sometimes the chemical environment is more amenable outside the cell than inside, sometimes buildup of the intermediates can disrupt other processes, sometimes that's just how it happens - biology is weird), and very often what you'll see is that a multi-step metabolic pathway can span across multiple different organisms - so, species 1 takes up a starting material, performs a handful of modifications, and then excrete the results outside the cell wall, and then another species will take up that substance and perform additional modifications on it, and this can run through several species before reaching the terminal state in the pathway (including the first species again). This works because each bacteria can have different enzymes and different internal chemistry which can affect how easy or likely a reaction is.
Nitrogen fixing is a notable example of this - it's not just one species in the roots of legumes responsible for taking N2 and converting it into ammonia, there's 6 or 7 that take part in that pathway.
There are recorded beliefs in medieval Germany, for instance, that carrying or wearing an eye from a bat will make you invisible.
Homeopathy however is pure nonsense even on a fundamental scientific level.
It is unfortunate that the two get conflated.
Now, to the question "Which folk medicines have a fairly robust (or at least promising) clinical basis?", there are certainly some: ginger[0], turmeric[1], honey[2], psilocybin[3], and of course capsaicin and peppermint. Not to mention sunshine, exercise, and meditation, all of which have traditional origins.
Taking a step back though, historically, pharmaceutical drugs have often been derived from natural remedies with bases in folk remedies. The pipeline from traditional medicine -> scientific study -> molecular isolation -> synthesis and mechanized production is pretty well-trodden. Aspirin comes from willow bark, morphine comes from opium, quinine (malaria treatment) comes from cinchona bark, paclitaxel (cancer treatment) comes from yew bark.
Homeopathy is BS though, no argument there. GP really shouldn't put it in the same bucket as folk medicine (it's not even particularly old).
[0] https://pmc.ncbi.nlm.nih.gov/articles/PMC9654013/
[1] https://pubmed.ncbi.nlm.nih.gov/36804260/
> There is no compelling scientific evidence that Oscillococcinum has any effect beyond placebo.
Does not sound promising