Does it really matter if I brew a stronger tasting cup of green tea in terms of absorbing antioxidants and oth?

I buy dried green tea leaves which have traces of cardamom in them what I want to know is that other than the bitter taste what difference does it make to boil green tea leaves in a pot of water as soon as the flame has started or to add the leaves after the pot is boiling and the flame is off. Does it affect the amount of antioxidant entering the system or anything?