As the OP has stated in a comment, this is the anime series Shinzo by Tetsuo Imazawa.
In the series, genetically-altered creatures known as Enterrans take over Earth and rename it in their own image called Enterra. Now three Enterrans have to protect the last human in order to find the hidden sanctuary called Shinzo and restore the human race. The anime focuses primarily on the adventures they undergo while working to accomplish this task.
In the first season, it is identified (Emphasis mine):
Mushra, Sago. and Kutal are then shown to be Hyper-Enterrans, Enterrans who can transform into stronger powered-up versions of themselves, these forms allow them to fight the various creatures that come after them. Throughout the first season the main characters fight a collection of Enterrans known as the Seven Enterran Generals, and various independent Enterrans where these Enterrans were either minions of the Seven Enterran Generals or bounty hunters. Each of these Generals rules a region that the gang travels through, which have different types of Enterrans, such as King Daku's land having a majority insect based Enterrans. The defeated Enterrans become En-Cards, which are card-like structures that can be used to increase power in both Enterrans and several machines such as Yakumo's vehicle Hakuba.