As one fruit is green, the other might not be fully ripe. It could be the angle showing the leaves differently, I can see a pronounced vein on your leaves, look at the one which is cut off on the right.
I think the strength of the spines might be to do with age, fruits are often on newer growth.
http://www.flickr.com/photos/2...
I tend to agree though that it doesn't quite match up, I found that by googling "'Mata-Cavalo Brasil" and only found the one photo for a start showing a flower and some spines so it was a good bet.
I have searched for Solanum fruits, I went to the 'show more results' and have found Solanum viarum. That is in the area and wide spread in Brazil. The description and most of the photos suggest the fruits turn yellow, but I found otherwise!
http://www.shirleydenton.com/p...
http://floradobrasil.jbrj.gov....
http://www.bugwood.org/weeds/f...
http://www.eattheweeds.com/ufo...
NOT EDIBLE: Solanum viarum, Solanum ciliatum, Solanum carolinense, all called Tropical Soda Apple or Horse Nettle, the first two turn red when ripe, the latter yellow. They usually start out with mottle green fruit. Some are toxic when green, others more toxic when ripe. Edibility is doubtful, botantical references vague, identification difficult. Best avoided. Of the three ripe S. ciliatum, now called Solanum capsicoides, might not kill you.
