I did a quick Google search on potato tree. This what I found. Don't know if it is good for rabbits but I would be careful giving especially to pregnant does.
Like other species in its genus, S. erianthum has a number of ethnobotanical and pharmaceutical uses. This is due to the presence of steroidal saponins, free genins, and steroidal alkaloids of the spirosolane group, such as solasodine and tomatidine. Alkaloids account for around 0.4% of the mass of dry berries and leaves. Steroidal alkaloids found in the plant are used by the pharmaceutical industry as precursors for the manufacture of synthetic steroids.
Potato Tree finds many uses as an herbal medicine in Tropical Asia. The leaves are believed to be very at ridding the body of impurities through the urine and are used for leukorrhea for that reason. The leaves are also used to induce abortion, while a poultice made from crushed leaves is used for hemorrhoids and scrofula. Heated leaves are applied to the forehead as an analgesic for headaches and a leaf decoction is used for vertigo. A root decoction is used to treat dysentery, fever, diarrhea, digestive problems, and violent body pains. The root bark is used as an anti-inflammatory and to treat arthritis. In West Africa, a decoction made from the leaves is used to treat leprosy, sexually-transmitted diseases, and malaria due to its laxative and diuretic effects.
I had never heard of a potato tree, so I googled it. The minute I saw the blossoms, I was suspicious. They look so much like nightshade and, indeed, potato tree is in the same family.
Potato tree's scientific name is Solanum erianthum and it is in the same family as garden potatoes, tomatoes, eggplant and the so-called deadly nightshade. The foliage of these plants is toxic and I would never willingly feed them to rabbits or anything else. They may not be drop dead poisonous, but they are not a healthy choice. For this reason, I would not feed the foliage of the potato tree to rabbits either.