Assessment of a 1H high-resolution magic angle spinning NMR spectroscopy procedure for free sugars quantification in intact plant tissue

Abstract

In most plants, sucrose is the primary product of photosynthesis, the transport form of assimilated carbon, and also one of the main factors determining sweetness in fresh fruits. Traditional methods for sugar quantification (mainly sucrose, glucose and fructose) require obtaining crude plant extracts, which sometimes involve substantial sample manipulation, making the process time-consuming and increasing the risk of sample degradation. Here, we describe and validate a fast method to determine sugar content in intact plant tissue by using high-resolution magic angle spinning nuclear magnetic resonance spectroscopy (HR-MAS NMR). The HR-MAS NMR method was used for quantifying sucrose, glucose and fructose in mesocarp tissues from melon fruits (Cucumis melo var. reticulatus and Cucumis melo var. cantalupensis). The resulting sugar content varied among individual melons, ranging from 1.4 to 7.3 g of sucrose, 0.4-2.5 g of glucose; and 0.73-2.83 g of fructose (values per 100 g fw). These values were in agreement with those described in the literature for melon fruit tissue, and no significant differences were found when comparing them with those obtained using the traditional, enzymatic procedure, on melon tissue extracts. The HR-MAS NMR method offers a fast (usually <30 min) and sensitive method for sugar quantification in intact plant tissues, it requires a small amount of tissue (typically 50 mg fw) and avoids the interferences and risks associated with obtaining plant extracts. Furthermore, this method might also allow the quantification of additional metabolites detectable in the plant tissue NMR spectrum.

Orthogonal Analysis Underscores the Relevance of Primary and Secondary Metabolites in Licorice

“…36 The 1 H NMR spectrum of fraction 1 was compared with the spectrum from commercial reference compounds (Figures S14 and S15, Supporting Information) and were in agreement with previously published data. 23,37,38 All identified metabolites were quantified in fraction 1 using 3,5-dinitrobenzoic acid (Fluka, TraceCERT) as the internal calibrant (IC, 2.12 mM). By far, 10 was the most abundant metabolite (71.7% in fraction 1, qHNMR, anomeric proton), followed by 11 (10.3% of fraction 1, qHNMR, H-3 resonance), 12 (2.91% of fraction 1, qHNMR, H-3 resonance), and 13 (0.16% of fraction 1, qHNMR, H-4 and H-6).…”

Recent Developments in Methods and Techniques for Rapid Monitoring of Sugar Metabolism in Fruits

“…Moreover, HRMAS spectra were developed for semisolid samples leading to a reduced extraction time (Santos and others ). Delgado‐Goni and others () quantified sucrose, glucose, and fructose in intact melons using HRMAS NMR within 30 min and there were no significant differences between the HRMAS NMR and enzymatic‐based results. On the other hand, quantitative HRMAS together with multivariate statistical analysis might represent a useful tool for sugar monitoring in fresh fruits, as with 1 H HRMAS NMR spectroscopy combined with PCA and assigned signal analysis.…”

High-resolution magic angle spinning nuclear magnetic resonance in foodstuff analysis

“…As expected, variations in amounts of soluble sugar among individual melons were observed. The comparison between sugar contents obtained by HR-MAS NMR with those determined by the enzymatic procedure (traditional methodology) revealed no significant differences, showing that HR-MAS NMR could be a valuable tool for quantifying compounds directly in their natural environment [78].…”