An attempt to cast light into lutein extraction and its alkali optimization

Abstract

The present study deals with optimization of alkali treatment including KOH concentration (20, 30, 40 and 50% w/v), treatment time (0, 10, 20, 40, 60 and 120 min) and temperature (30, 50, 70 and 90 °C) in order to eliminate the green pigments (chlorophyll residues) of lutein acetone extract from spinach. Based on spectrophotometric and RP-HPLC-PDA analyses, alkali treatment (KOH 30% w/v) at 50 °C for 40 min with 4:1 mass ratio (extract: alkali solution) were the optimum conditions to eliminate chlorophyll residues of spinach leaf powder (extracted with acetone for 12 h). As a result, the lutein content of the alkali treated extract was measurable (1.85 mg/g dry weight basis), whereas its quantification was unlikely due to the interferences of green and orange pigments. Regarding the lutein content of marigold petals (14.48 mg/g dry weight basis) extracted by acetone for 6 h, it was noticed that heat treatment alone (50 °C for 40 min without KOH) was ineffective, while by combination of alkali and temperature (KOH 30% w/v, for 40 min at 25, 50 or 70 °C) the lutein content was significantly (p < 0.05) decreased. Moreover, the HPLC quantification of alkalized spinach acetone extract showed an increase (up to 33%) compared to rudiment specimen. Apart from lutein, some other carotenoids (i.e., neoxanthin, violaxanthin, zeaxanthin and β-carotene) were also identified and quantified.