Optimisation of Lutein Extraction From Gac (Momordica cochinchinensis) Fruit Peel and Evaluation of In Vitro Eye Protective Effects of the Extracts

Lutein is a macular biopigment that can protect the retina from oxidative stress induced by chronic exposure to light and oxidants. The peel of gac fruit ( Momordica cochinchinensis ) contains high levels of lutein, but the extraction optimisation parameters are complex, requiring saponification, and the effects on ocular bioactivity are not well understood. This study is aimed at optimising parameters for lutein extraction validated using HPLC from gac peel to determine their protective effects on oxidatively stressed retinal cells. The factors investigated for optimisation were KOH concentration, time, and temperature using (1) single factor, (2) multiple factor response surface methodology, and (3) predictive modelling. The optimum conditions for lutein extraction using single factors were 9% KOH for 3 h at 60°C, multiple factors were 9% KOH for 3 h at 45°C, and predictive modelling was 18% KOH for 1.9 h at 39.9°C, with the maximum extraction of lutein at 12.37, 15.64, and 17.4 mg/g DW, respectively. The extracted lutein purity and chemical composition were compared using HPLC and FTIR and indicated high purity and similarities in all extracts including the commercially purified lutein. Lutein extracted exhibited benefits on oxidatively stressed retinal pigment epithelium (RPE) cells that reversed damage to baseline unstressed levels exceeding 80% viability, similar to purified lutein standards. The feasibility of gac lutein and extraction optimisation were discussed for commercial translational opportunities as a medicinal bioproduct with a focus on eye benefits.