Effect of light wavelength on cell growth, content of phenolic compounds and antioxidant activity in cell suspension cultures of Thevetia peruviana.

Thevetia peruviana (T. peruviana) has been considered as a potentially important plant for industrial and pharmacological application. Among the number of compounds which are produced by T. peruviana, antioxidants and polyphenols are of particular interest due to their benefits on human health. Cell suspension cultures of T. peruviana were established under different conditions: 1) constant illumination (24h/day) at different light wavelengths (red, green, blue, yellow and white), 2) darkness and 3) control (12h/12h: day light/dark) to investigate their biomass, substrate uptake, polyphenols production and oxidizing activity. The results showed biomass concentrations between 17.1g dry weight (DW)/l (green light) and 18.2g DW/l (control) after 13days. The cultures that grew under green light conditions consumed completely all substrates after 10days, while other cultures required at least 13days or more. The total phenolic content was between 7.21 and 9.46mg gallic acid (GA)/g DW for all light conditions. In addition the ferric reducing antioxidant power and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid antioxidant activity ranged from 5.41-6.58mg ascorbic acid (AA)/g DW and 82.93-110.39μmol Trolox/g DW, respectively. Interestingly, the samples which grew under the darkness presented a higher phenolic content and antioxidant capacity when compared to the light conditions. All together, these results demonstrate the extraordinary effect of different lighting conditions on polyphenols production and antioxidant compounds by T. peruviana.