Yes — the white flesh of mangosteen is safe and antioxidant-rich. Offer the segments, avoiding the bitter purple rind.
Keeper's noteOpen it and offer just the white segments. Remove any seeds. The rind isn't for eating — it's bitter and tannin-rich.
Why mangosteen is good for parrots
Mangosteen's soft white segments are non-toxic and contain antioxidants (xanthones) and vitamin C. The thick purple rind is intensely bitter and astringent (high in tannins), so only the inner flesh is offered. Larger segments may contain a soft seed to remove.