Ben Old hadt the Allstars ahead after five minutes and goals from Nicolas Milanovic and Adam Taggart made it 3-0 before half-time.
Apostolos Stamatelopoulos scored twice after the break before Jake Hollman, Jordan Courtney-Perkins and Bozhidar Kraev closed out the victory for the hosts.
Afterwards, Newcastle boss Eddie Howe said: "That was a tough one for our young lads. You can see probably the gap between experience and youth," said Howe.
"I don't think we could have (played any of the first-team players), especially when you combine the travelling time that we've had and the quick time between games, it was too big of a risk of injuries and we couldn't afford that.
"I think just too many mistakes, forced by the All Stars playing well. A lot of our players need to reflect on that and see what they need to do to come back stronger."