Here is the one paper I found which noted mitochondrial effects of cuminaldehyde. It says:
Basically this study found that cuminaldehyde caused a decrease in the electrical voltage across the mitochondrial membrane.
Now although that decrease in voltage would normally equate to a loss of power in the mitochondria, I guess it's possible that in the context of the dysfunctional mitochondria and energy metabolism of ME/CFS, that reduced voltage might have a beneficial effect.
For example,
this paper finds that a mild reduction in mitochondrial membrane potential still allows ATP to be generated, but has the advantage of lowering reactive oxygen species created by the mitochondria.
Oxidative stress is considered to be a problem in ME/CFS, and a lot of oxidative stress arises in mitochondria.
So by slightly reducing mitochondrial power output, cuminaldehyde may be reducing the oxidative stress generated in ME/CFS patients.
As an aside, on
@mitoMAN's ME/CFS discord server, there was a whole channel dedicated to a weight loss drug called 2,4-dinitrophenol (DNP), which similarly reduces mitochondrial power output, and which one patient with an ME/CFS-like illness found greatly improved his fatigue when taken at very low doses (about 3 mg of DNP daily).
DNP reduces mitochondrial ATP output, and in this way, reduces the amount of reactive oxygen species pumped out by mitochondria.
Some studies have suggested that low-dose DNP could have a protective effect in neurological diseases involving reactive oxygen species.
A few ME/CFS patients tried low-dose DNP on the discord server, but unfortunately none were able to replicate the benefits the original ME/CFS patient was obtaining.
But if cumin is anything to go by, cumin only works for a small subset of ME/CFS patients, and DNP might be the same.