Hi Myriam!
Regardless of a positive ID, you know that you have an unusual plant in the Coffee Family, Rubiaceae. You may have found something unusual and rare.
Janet has provided a great reference source. Folks are looking and interested.
If you can provide any more sample / photos, maybe more can be figured. Nice to learn new stuff!
The Hawaiian
Psychotria can become a large tree.
This is
Psychotria mauiensis. (Excuse the photo quality. They're from the other side of the Island, in hard to get to areas.)
