Barca jumped to a 3-0 lead on Tyneside through Xavi Espart and a double from Oscar Gistau before halftime.
However, Newcastle fought back after the break as Leo Shahar and substitute Kacey Wooster struck, but the hosts ran out of time to find an equaliser.
Afterwards, Wooster told ChronicleLive: "It’s a proud moment, a bit surreal, but it’s unfortunate with the result.
“We have to put things right in the next game. (Coach Adam Lawrence) just said to be myself, that’s what you’ve got to do really. You’re there for a reason, you’re in the squad for a reason and to be myself, play my own game and everything will sort itself out.
“It was a good experience, they were tough to play against but it’s best to come up against the best and test yourself.”