Changes in the phenolic compounds and antioxidant capacity of Berberis microphylla G. Forst. berries in relation to light intensity and fertilization

The objective of this study was to evaluate the qualitative and quantitative composition of the phenolic compounds and the antioxidant activity of B. microphylla fruit under different light intensities and levels of fertilization during two production years. Total monomeric anthocyanin concentration in high light intensity conditions was three times more than that obtained at medium light intensity, expressed for both fresh weight and dry weight terms (299.7 mg/100 g FFW and 9.5 mg/g DFW, respectively). However, in the case of total polyphenol concentration, minor increases of 30 and 11% appeared under high light intensity in comparison with medium light intensity (906.6 mg/100 g FFW and 30.7 mg/g DFW, respectively). Scavenging activity on DPPH was increased from 56.0 to 66.8% under the high light intensity treatment. This was also true for the reducing power which increased from 40 to 46.2%. Fertilizers reduced the flavonoid concentration, but increased the total polyphenol concentration at fertilization level 2. In the case of flavonoids, the maximum contents in fruits were 200.2 and 7.6 mg (+)-catechin equivalents/100 g FFW and DFW, respectively in the control treatment. The total polyphenol concentration was the highest (856.1 and 31.2 mg tannic acid equivalents/g FFW and DFW, respectively) with the level fertilization 2. The scavenging activity on DPPH was from 60.3 to 62.8% when raising the fertilization level from 0 to 2, while the reducing power varied between 40.5 and 44.3% at levels 1 and 2. The total monomeric anthocyanin concentration increased with the level of fertilization in the fruits of plants at high light intensity, whereas the trend was inversed in those under medium light intensity. Hence, these studies display the possibility for maximizing both the productivity and the antioxidant capacity of fruits by crop management.