Orthosiphon stamineus (Java tea) is a leaf that is commonly brewed as a tea for a variety of purposes, but said purposes (beyond just liking the taste of the tea) tend to revolve around treating inflammatory disorders or treating ailments of the urogenital tract. It originates from the oceanic region and was introduced to mainland Asian countries and the West sometime near the beginning of the 20th century.
It is currently in preliminary stages of research and a lot of research is a bit complicated since it all originates from one research group located in Malaysia and needs to be replicated independently of the country from which it originated from (potentially a problem for scientific validity, since some studies investigating local herbs tend to be over promising in their effects and this excessive promise is attenuated a bit when other research groups look at it).
Nevertheless, there appears to be promise for this herb as a fat burner since the 70% ethanolic extract has been noted in two studies to stimulate leptin production in fat cells and increase in leptin have been noted in serum following oral ingestion of the leaf; reductions in food intake have been noted at only higher levels of intake, but are still thought to be associated with leptin.
While there is potential for this leaf as an antiinflammatory agent and diuretic, it has no practical research for the former that shows promise and while the evidence for the latter is a bit promising in rodents (does not exceed reference drugs in potency) the lone human study on the topic failed. There is one very promising study on colon cancer which definitely needs to be replicated by another research group, since reasonable oral intakes of the leaves potently suppressed colon tumor growth in mice.
All in all, pending future research this can be a potential new non-stimulatory fat burner for lean persons especially; we need quite a bit more evidence to confirm this though.