Let A and B be two unital prime complex *-algebras such that A has a nontrivial projection. In this paper, we study the structure of the bijective mappings Φ ∶ A → B preserving sum of products α 1 ab * + α 2 b * a + α 3 ba * (resp., α 1 ab * + α 2 b * a + α 3 a * b), where the scalars {α k } 3 k=1 are rational numbers satisfying some conditions.