First of all, here is a table of carb. and two mineral contents of a few fruits:

        Carbohydrate   calcium  magnesium

grapes        17              14       5
cranberries   13               7       7
blueberries   14               6       5
oranges       12              40      10
passion fruit 14               4      17

I don't have any table providing *sugar* content, unfortunately, but we see from
the above that there are no striking differences between sweet fruits (grapes)
and sour ones (passion fruits, cranberries). The fact that a fruit doesn't taste
sweet doesn't mean it has a low mineral or even carbohydrate-content, and thus a
fruit can score high in Brix even though it is virtually inedible raw (has
anyone tried raw cranberries?)

Second of all, even if some wild fruits contain a fair amont of carbohydrate
(although probably less than artificially selected fruit), their glycemic index
is low thanks to their high-fiber content, so eating too much modern fruit is
more problematic than eating too much wild fruit.

P.S. To end this "fruitless" discussion, it would be helpful to have a
comparison of modern cultivated fruit and their wild counterparts, with the
sugar contents expressed as percentages, but unfortunately I have never seen
such a table.

JL