Xanthophylls or carotenols are oxygen derivatives of carotenes with molecular formula C40H56O2 e.g. lutein, zeaxanthin. These are also accesory pigments which absorb light and transfer the energy to chlorophyll.
Why Rubisco is not affected by O2 in C4 plants ?
O2 is formed in mesophyll cells while Rubisco is present in bundle sheath cells. Therefore Rubisco does not come in contact with O2 and is thus not affected by it.