2.1. Plant materials
Green leafy vegetables were collected from three different supermarkets in Malang area (East Java, Indonesia).
All samples were purchased early in the morning, transported into laboratory and directly measured by in vivo
procedure for SPAD value and % N. Then, the samples were stored at -18 °C deep freezer for further in vitro
analysis. The whole experiment was accomplished during May 2014 until June 2014.