Analysis of Nutrient Functional Components and Antioxidant Activity in Leaves of Introduced Fruit and Leaf Mulberries

Clarifying the nutritional and antioxidant characteristics of introduced mulberry leaves aids development and utilization in Hexi region, China. The main nutrients and functional components of fruit and leaf mulberries, and correlations between antioxidant capacities of their leaf extracts, were investigated. Crude protein, crude fat, reduced sugar, and ash contents of leaf mulberry were significantly higher than those of fruit mulberry (P<0.05), while differences in γ-aminobutyric acid and rutin in leaves of these two cultivars were not significant (P>0.05). Flavonoid concentrations in leaf mulberry (50.57 mg.g⁻¹) were significantly higher than in fruit mulberry (46.96 mg.g⁻¹) (P<0.05), but differences in polyphenol and crude polysaccharide concentrations between them were not significant. Mineral contents in fruit and leaf mulberry leaves were high in potassium and low in sodium, and occur in the order K>Ca>Mg>Na>Fe. Leaf mulberry K, Mn, Zn, Cu and Ni contents were higher than those in fruit mulberry, while the opposite holds for Ca, Mg, Na and Fe contents. The Index for Nutritional Quality (INQ) of Na, crude fat, and reduced sugar contents in fruit and leaf mulberry leaves were<1, while K, Mn, Ca, Mg, Zn, Fe, Cu, and crude protein contents were>1. Additionally, nutrition equivalent (NEU) from leaf mulberry exceeds that of fruit mulberry. Flavones and polysaccharides in fruit mulberry have higher DPPH radical clearance activity than leaf mulberry, but flavonoids in leaf mulberry had higher radical clearance of ABTS⁺ than fruit mulberry. There was little difference in polysaccharide clearance of ABTS⁺ between the two cultivars. Highly significant positive correlations (correlation coefficients ranging 0.899~0.991) in flavonoid, rutin, polyphenol and polysaccharide content DPPH radical scavenging exist between the two cultivars. There was no significant difference in the ABTS⁺ free radical scavenging rate. The nutritional function and antioxidant activity of leaf mulberry exceed those of fruit mulberry, which was more suitable for the Hexi region.