In vivo retinoid metabolic and visual cycle pathways assessment of carotenoid-rich refined red palm-pressed mesocarp olein

The Palm-pressed mesocarp is a by-product from the palm oil mill and is comprised of 5–7 % of residual oil, which could be further refined into red palm-pressed mesocarp olein (PPMO). This study aimed to obtain the chemical profile of PPMO and assess its eye health effects through retinoid metabolic and visual cycle pathways regulation. PPMO contains exceptionally high vitamin E (1819.0 ppm) and carotenoid (1113.8 ppm) contents with a similar fatty acid composition to palm olein. The rats fed with 2 g/kg PPMO daily for 84 days through oral gavage up-regulated the retinol and retinyl palmitate levels, as well as the mRNA and protein expression levels of RBP4 in blood, CRBP1 and LRAT in the liver, RPE65 and RDH5 in the eye. The outcomes showed that PPMO showed comparable regulation effects with β-carotene in the retinoid metabolic and visual cycle pathways, revealing it as a phytonutrient-rich edible oil with beneficial eye health effects.