Effect of the main factors that influence the phytochemical composition of Morus alba (Linn.)

Danny Eugenio García Marrero
Estación Experimental de Pastos y Forrajes Indio Hatuey, Central España Republicana 44280, Matanzas, Cuba

ABSTRACT
In order to evaluate the main factors that influence the phytochemical composition of M. alba (Linn.), two trials were conducted, in which the secondary metabolism and nitrogen fraction were characterized. Through phytochemical sieving, 15 groups of metabolites were studied, from which phenols, flavonoids, coumarins, soluble carbohydrates, steroids, alkaloids and saponins, were detected. Through a cluster analysis it could be proven that the regrowth age was the variable of higher incidence on the performance of secondary metabolites in both seasons. The TP were found in the leaves in a range of 1,26-3,26 % DM and in the fresh stems between 0,77 and 2,50 % DM; a marked effect of the edible fraction parts was observed. The flavonoids in the leaves were present in levels of 1,50-1,76 % DM and in the fresh stems between 0,69 and 1,72 % DM; no significant effect was observed of the factors variety, fertilization and season. For the coumarins the concentrations in the leaves oscillated between 0,43 and 0,79 % DM and in the fresh stems between 0,42 and 0,80 % DM; the combination of the factors Variety x Fertilization generated the highest differences. The SCH in the leaves were found between 10,40 and 18,78 % DM and in the fresh stems between 3,86 and 10,92 % DM. The factor with the highest influence on the results was the analyzed plant part. The TS levels showed large variations with the season, mainly in the leaves, where the contents were 4,08-16,65 mg/g DM; in the fresh stems the concentrations oscillated between 0,90 and 3,76 mg/g DM. The variety Cubana showed differences in the trends of the phenolic compounds in the DS. In the second trial the CP concentration varied between 17,02 and 22,40 % DM in the leaves and between 7,72 and 9,68 % DM in the fresh stems. The highest differences in the concentrations were found between the leaves and fresh stems, followed by the cutting frequency. The TP showed values between 11,18 and 19,91 % DM in the case of leaves and between 4,17 and 9,00 % DM in the fresh stems. Similarly to the CP, the edible fraction parts and the defoliation frequency were the factors that differentiated the most the concentrations; the combination of the factors variety and fertilization provided the most differentiated characteristics among the varieties in leaves and stems. The variety Cubana also showed differences in the trends observed with the increase of fertilization. It was observed that with the increase of the regrowth age, in the leaves as well as the fresh stems, the protein quality expressed as TP (% CP) increased. The studies conducted allow to state that the factors fertilization, variety and season created discreet numeric variations among treatments, although there was a trend of the varieties to be differentiated when they were combined with the factor fertilization. The concentrations of secondary metabolites and nitrogen fraction of M. alba were primarily affected by the regrowth age and the differences found between the edible fraction parts of the plant.