EVALUATION OF BIOATIVE COMPOUNDS AND ANTIOXIDANT ACTIVITY OF EXTRACTS OF BLACK MULBERRY LEAVES (Morus nigra L.) USING EXPERIMENTAL DESIGN

Extracts of black mulberry leaves present phytochemicals such as phenolic compounds and minerals. These substances have been studied because they show several health benefits. In this work we report the influence of drying temperature, infusion temperature and extraction time by means of factorial design monitoring the total phenolic content (CFT) of aqueous extracts of leaves of Morus nigra L. The concentrations of CFT, flavonoids, flavonols and antioxidant activity of the extracts were determined by spectrophotometry. The identification and quantification of phenolic compounds were performed by LC-ESI-MS / MS. The determination of the mineral concentration in the black mulberry leaves was performed by ICP-MS. The Pareto and surface response graphs suggested that the most efficient extractions occurred for leaves drying at lower temperatures and using higher infusion temperatures, extraction time did not show significant influence. The extracts presented concentration of CFT from 16.96 ± 0.15 to 5.73 ± 0.33 mg GAE g-1. The analyzes by LC-ESI-MS / MS allowed to identify phenolic substances not yet reported in the literature to date. In addition 10 mineral elements were determined in the black mulberry leaves at mg kg-1 concentrations range.

黑桑叶片提取物含有酚类化合物、矿物质等多种植物化学物质。此类物质因具备多项健康益处而受到广泛研究。本研究采用析因设计，以黑桑（Morus nigra L.）叶片水提取物的总酚含量（Total Phenolic Content, 简称CFT）为监测指标，探究干燥温度、浸提温度与提取时间对提取过程的影响。采用分光光度法测定提取物的总酚、类黄酮、黄酮醇含量以及抗氧化活性。通过液相色谱-电喷雾电离串联质谱（LC-ESI-MS/MS）完成酚类化合物的定性与定量分析。采用电感耦合等离子体质谱（ICP-MS）测定黑桑叶片中的矿物质元素浓度。帕累托图与响应面图分析结果显示：采用较低温度干燥的叶片、搭配较高浸提温度时，提取效率最优，而提取时间对提取效果无显著影响。提取物的总酚含量范围为5.73±0.33至16.96±0.15 mg没食子酸当量（GAE）/g。经液相色谱-电喷雾电离串联质谱分析，本研究鉴定出了迄今文献尚未报道的酚类物质。此外，本研究以mg/kg为浓度单位，测定了黑桑叶片中的10种矿物元素。