By "African slave trade" I'm assuming you mean the Atlantic Slave trade. Slave trade had been going on for centuries in Africa (as elsewhere) before Europeans bought slaves to send to the New World. Most interaction sub-Saharan Africa had with the world was with the Islamic world. Mansa Musa on his pilgrimage to Mecca spent so much gold that the Mediterranean (particularly Egypt) faced mass inflation. The east coast of Sub-Saharan Africa was also very involved in India Ocean Trade which helped develop bustling cities such as Safala, Mombasa, Kilwa, and Mogadishu.

I am by no means an expert in this area, so I am sure others can provide much more information (and better sources)