To make things a lot easier - this is a typical 3 phase boss with him sticking his tongue out at the end of each phase. However, unlike many similar bosses you can take as long as you want to grab the orb from his mouth.
As a result you can wait for the health plants (and ammo plants) to recharge before moving onto the next phase - in other words you can start each phase with full energy.
In terms of beating him use the Bombegranates on the lower zits (?) and the pistol on the higher up ones. If you are quick with the shooting the flying enemies don't have enough time to destroy you before you take down another phase...