2. Materials and methods
2.1. Samples
The fresh and mature leaves of the plant, water spinach (I. aquatica cv. Slim leaf), which was usually cultivated and consumed in central and southern China ( Zhu et al., 2010), were obtained in a local supermarket (Wuhan city, Hubei Province, central of China) in July 2009. Water spinach samples (100 g) were washed and mixed with 100 mL deionized water, these fresh mixtures were for further carotenoid extraction after homogeneous treatment.