Answer:
Before the 15th century, the region that benefited the most from trade was East Africa, which fell under the islamic world sphere of influence. The islamic rulers established trade with places all over the read sea and the arab sea. They not only traded goods but also people, who they bought and sold as slaves, as the europeans would start doing a few years later.
As for West Africa, before the contact with europeans, the region was dominated by many rivalling kingdoms who traded among themselves. The Mali Empire was perhaps the most important of this kingdoms.