I lightened a set banana stain with sodium bisulfite which is a reducing bleach. But, it did not completely remove the stain. See
https://en.wikipedia.org/wiki/Bleach#Reducing_bleaches
It may be worth trying a stronger reducing bleach such as sodium dithionite. This product is 30% sodium dithionite:
https://www.ebay.com/itm/Carbona-COL...A/222507901994