Quantitative ¹H-NMR Spectroscopy for Profiling Primary Metabolites in Mulberry Leaves.

Qianqian Liang,Qiuying Wang,Jia Hao,Ya-Nan Wang,Miaomiao Jiang,Yuan Wang

doi:10.3390/molecules23030554

Abstract

The primary metabolites in aqueous extract of mulberry (Morus alba L.) leaves were characterized by using proton nuclear magnetic resonance (1H-NMR) spectroscopy. With the convenience of resonance assignment, GABA together with the other 10 primary metabolites was simultaneously identified and quantified in one 1H-NMR spectrum. In this study, external calibration curves for metabolites were employed to calculate the concentrations of interests. The proposed quantitative approach was demonstrated with good linearity (r2 ranged in the interval of 0.9965–0.9999), precision, repeatability, stability (RSD values in the ranges of 0.35–4.89%, 0.77–7.13% and 0.28–2.33%, respectively) and accuracy (recovery rates from 89.2% to 118.5%). The established 1H-NMR method was then successfully applied to quantify 11 primary metabolites in mulberry leaves from different geographical regions within a rapid analysis time and a simple sample preparation procedure.

Highlights

Mulberry leaves are the main food of silkworm, with a long history of industrial use for more than 5000 years [1], and they are used as functional foods for humans concerning their nutritive and medicinal values
Phytochemical studies reveal that γ-aminobutyric acid (GABA) is one of the principal components isolated from the extracts of mulberry leaves [5]
Like many other aliphatic amino acids, GABA lacks a suitable chromophore for direct ultraviolet detection, and sample derivatization is required before injection to liquid chromatography [11]

Summary

Introduction

Mulberry leaves are the main food of silkworm, with a long history of industrial use for more than 5000 years [1], and they are used as functional foods for humans concerning their nutritive and medicinal values. Mulberry tea has been developed to be a popular health food loved by consumers on account of its effects on modulating dyslipidemia, preventing diabetes, and maintaining health [2,3]. The extracts of mulberry leaves are reported to display a wide range of significant biopharmaceutical activities, including antidiabetic, antibacterial, anticancer, cardiovascular, hypolipidemic, antioxidant, antiatherogenic, and anti-inflammatory effects [4]. Phytochemical studies reveal that γ-aminobutyric acid (GABA) is one of the principal components isolated from the extracts of mulberry leaves [5]. GABA is well known for its essential role in the nervous system and brain development [6], and may be associated with several of the physiological activities of mulberry leaves, such as antioxidant [7], antihyperglycaemic [8], antihypertensive [9], and anti-inflammatory properties [10]. The pre-column derivatization process is time-consuming, can add impurities into samples, and makes the analysis more complex

Methods

Results

Conclusion