Changes in biomass allocation and phenolic compounds accumulation due to the effect of light and nitrate supply in Cecropia peltata plants

Cecropia peltata is popularly known as "guarumbo" in Mexico and is used in traditional medicine for treatment of diabetes mellitus. C. peltata plants were cultivated in a hydroponic system under controlled conditions. Gradients of light (20, 30 and 100 μmol m^-2 s^-1) and nitrate concentrations (13, 2 and 0. 2 mM) were applied to estimate their effect on biomass allocation and accumulation of bioactive (chlorogenic acid and isoorientin) phenolic compounds over a 28-day period. According to carbon nutrient balance (CNB) hypothesis predictions, biomass accumulation in foliage was stimulated by the highest irradiance (100 μmol m^-2 s^-1); similarly, at highest irradiance in combination with lowest nitrate concentration (0. 2 mM), root growth was stimulated (root-to-shoot ratio increased twofold with respect to the control). In these conditions, total phenolics (TP) and chlorogenic acid (CGA) contents were higher in aerial parts than in roots, with a 3. 8-fold increase in TP and a 7. 7-fold increase in CGA in foliage with respect to the control plants. Isoorientin was accumulated at very low levels. Antioxidant activity and total phenolic content showed a strong positive correlation. Phenylalanine ammonia-lyase activity (PAL) in aerial parts exhibited significant changes (&twofold) by highest irradiance. C. peltata plants allocate biomass and/or phenolic compounds to compensate the oxidative damage (increase in MDA levels) due to changes in light and nitrate restriction. The results are the basis for the establishment of a system of C. peltata culture in view of the potential use of C. peltata in therapeutic preparations for the treatment of diabetes mellitus.