Determination of major carotenoids in a few Indian leafy vegetables by high-performance liquid chromatography

Leafy vegetables Basella rubra L., Peucedanum sowa Roxb., Moringa oleifera Lam., Trigonella foenum-graecum L., Spinacia oleracea L., Sesbania grandiflora (L.) Poir., and Raphanus sativus L.] that are commonly used by the rural population in India were evaluated in terms of their main carotenoid pattern. The extracted carotenoids were purified by open column chromatography (OCC) on a neutral alumina column to verify their identity by their characteristic UV-visible absorption spectra. Reverse-phase high-performance liquid chromatography (HPLC) on a C18 column with UV-visible photodiode array detection under isocratic conditions was used for quantification of isolated carotenoids. Acetonitrile/methanol/dichloromethane (60:20:20 v/v/v) containing 0.1% ammonium acetate was used as a mobile phase. The major carotenoids identified by both methods were lutein, beta-carotene, violaxanthin, neoxanthin, and zeaxanthin. Among the carotenoids identified, lutein and beta-carotene levels were found to be higher in these leafy vegetables. Results show that P. sowa and S. oleracea are rich sources of lutein (77-92 mg/100 g of dry wt) and beta-carotene (36-44 mg/100 g of dry wt) compared with other leafy vegetables. The purity of carotenoids eluted by OCC was clarified by HPLC, and they were found to be 92% +/- 3% for neoxanthin, 94% +/- 2% for violaxanthin, 97% +/-2% for lutein and zeaxanthin, and 90% +/- 3% for beta-carotene. It could be recommended to use P. sowa and S. oleracea as rich sources of lutein and beta-carotene for health benefits. The OCC method proposed is relatively simple and provides purified carotenoids for feeding trials.