The fighter, 23, later told how she took Araujo to ground in a "rear-naked choke" before locking him in a "triangle choke" for 20 minutes until police arrived.
Ms Bastos told Brazil's iG website: "One of the guys grabbed the mobile phone I was carrying. I could see that they were not armed so I knocked their motorbike down.
"I wasn't afraid. I knew I could immobilise them.
"One of them managed to run away, so I got the motorbike driver with a 'lion killer' and held him in my legs for 20 minutes."
The 'lion killer' is a choke hold in Brazilian jiu-jitsu where the attacker wraps his arm around his opponent's neck, placing the crook of his elbow on his trachea.
In the video filmed on an onlooker's mobile phone, Arauju is heard screaming out for help as Ms Bastos holds him in the lock and applies pressure on his neck.
He shouts: "Daddy, daddy, call the police, daddy. Help Jesus. I swear, it was the first time I've ever done this. Help, Lord, somebody help me. Where's my mum?"
Araujo was taken to the local police station, where he denied trying to rob the women, according to reports.