Coutinho, who arrived from Liverpool in January, and Dembele, whose debut season in Spain has been thwarted by fitness problems, are the new additions.
"We're not naive and can see what's happening around us," Catalonia-born striker Gerard Deulofeu said. "But I'm not here to talk about politics."
Barcelona hope record signing Dembele could be back in action in three and a half months after successful surgery.
Barcelona coach Ernesto Valverde could make changes in defense with Sergi Roberto, Aleix Vidal and Lucas Digne.
Barca are still coming to terms with the loss of Neymar to Paris Saint-Germain for a world record 222 million-euro fee.
The Catalan giants splashed out on Demeble to fill the gap left by Neymar's world record 222 million-euro move to PSG.
Barcelona manager Valverde swatted down talk of star striker Neymar departing for a world-record transfer to PSG.
Ernesto Valverde resigned from Athletic Bilbao on Tuesday with the hope of taking over at Barcelona next season.