The above article is about African nightshades in sub-Saharan Africa, and it's fascinating. It mentions some of Solanum retroflexum's nutritional value (its leaves in particular). I only refer to Solanum retroflexum as wonderberries. The other nightshades are something else.
However, it should be noted that wonderberries are improved, and that they were bred in the USA, by Luther Burbank. They're not a wild species. I'm sure they'd flourish in Africa, though! They certainly flourish in my garden (while two kinds of Solanum nigra had trouble in it).