
Mango liqueur is a sweetened liqueur made by steeping or blending ripe mango into a neutral spirit base.
Sweetness and body are easy to match; the resinous tropical note is the half that does not transfer, and no adjustment of measure brings it back.
Stone fruit at matching sweetness, and it pours one for one by volume; what goes missing is the resinous tropical note that mango has and peach does not.
Mango purée with syrup
Brighter, livelier fruit with no strength in it: make that up with neutral spirit, roughly on par with the purée. It also thickens the drink.
Mango depends on lactones and esters, which do not survive indefinitely once air is in the bottle. Nothing spoils. What happens is that a distinctive tropical bottle turns into a generic sweet one over a year or so.