Ashton Kutcher -- I Got Nothing to Say About Demi Moore

Ashton Kutcher had no answer when asked if Demi Moore was okay following her nitrous oxide-induced medical emergency -- hopping wordlessly into a car beside a blonde mystery woman Tuesday night.

The video was shot as the actor was leaving a nightclub in Sao Paulo, Brazil -- an agency photog asks, "Is Demi okay?" ... and Ashton keeps mum, piling into an idling vehicle with two acquaintances, one female.