Estimation of the phenolics content of St. John's wort (Hypericum perforatum L.) grown under different water and salt levels based on reflectance spectroscopy

Abstract

Accumulation of phenolics were examined in greenhouse-grown Hypericum perforatum plants as effected by three different salts, which were MgSO4, CaCl2, and NaCl in the salt concentrations of 0.03 (control), 1, 2.5, 4, and 8 dS m(-1) for each salt. Three different water levels, which were 80, 100, and 120% were applied to all three salts mentioned above. Multi regression analyses were performed to describe the effects of water and salt levels on phenolics accumulation. As a result of ANOVA and multi-regression analysis, it was found that there was close relationship between actual and predicted phenolic contents in Hypericum perforatum. HPLC analyses were used to determine quercetin, quercitrin, isoquercetin, hyperoside, rutin, and cholorogenic acid contents. The relationships between different water and salt levels, and phenolics accumulation were determined by spectral reflectance values. The r values for quercetin, quercitrin, isoquercetin, hyperoside, rutin, and cholorogenic acid were determined as 0.83, 0.82, 0.91, 0.88, 0.84, and 0.87, respectively. All r-values and standard errors of the equations were found to be significant at the p<0.001 level.