Molecular structure, stability and cytotoxicity of natural green colorants produced from Centella asiatica L. leaves treated by steaming and metal complexations.

Stability of extracts from Centella asiatica L. leaves treated by steaming and metal-chlorophylls complexations against combined acid-heat was compared with that from untreated leaves and synthetic colorant. Formation of metal-chlorophylls complexes was confirmed by FTIR spectroscopy. Molecular structure changes during stability test and cytotoxicity of the extracts against Vero cells were evaluated. Utilization of the extracts as colorant was also assessed in selected beverage ingredient and food. Copper-chlorophylls extracts exhibited similar green hue to those from untreated and steamed leaves, while zinc-chlorophylls extracts exhibited yellow-green color. Metal-chlorophylls extracts possessed higher stability against combined acid-heat than those from untreated and steamed leaves. Use of metal-chlorophylls extracts in beverage ingredient led to increased hue value due to their structural rearrangement, which was confirmed by changes in Q band of VIS spectra. Cytotoxicity of zinc- and copper-chlorophylls extracts was slightly different and higher than those of extracts from untreated/steamed leaves and synthetic colorant.