Effect of Elicitation with Iron Chelate and Sodium Metasilicate on Phenolic Compounds in Legume Sprouts.

Henryk Dębski,Wiesław Wiczkowski,Marcin Horbowicz

doi:10.3390/molecules26051345

Abstract

Seven-day-old sprouts of fenugreek (Trigonella foenum-graecum L.), lentil (Lens culinaris L.), and alfalfa (Medicago sativa L.) were studied. The legume seeds and then sprouts were soaked each day for 30 min during 6 days with water (control) or mixture of Fe-EDTA and sodium silicate (Optysil), or sodium silicate (Na-Sil) alone. Germination and sprout growing was carried out at temperature 20 ± 2 °C in 16/8 h (day/night) conditions. Phenolic compounds (free, ester, and glycosides) content were determined by HPLC-ESI-MS/MS using a multiple reaction monitoring of selected ions. Flavonoids and phenolic acids were released from their esters after acid hydrolysis and from glycosides by alkaline hydrolysis. The presence and high content of (−)-epicatechin (EC) in fenugreek sprouts was demonstrated for the first time. Applied elicitors decreased the level of free EC in fenugreek and alfalfa sprouts but enhanced the content of its esters. Besides, elicitors decreased the content of quercetin glycosides in lentil and fenugreek sprouts but increased the content of quercetin and apigenin glycosides in alfalfa sprouts. The applied elicitors decreased the glycoside levels of most phenolic acids in lentil and p-hydroxybenzoic acid in fenugreek, while they increased the content of this acid in alfalfa. The mixture of iron chelate and sodium silicate had less effect on changes in flavonoid and phenolic acid content in legume sprouts than silicate alone. In general, the used elicitors increased the content of total phenolic compounds in fenugreek and alfalfa sprouts and decreased the content in lentil sprouts. Among the evaluated elicitors, Optysil seems to be worth recommending due to the presence of iron chelate, which can be used to enrich sprouts with this element.

Highlights

An alternative method of increasing the nutritional value of food is to germinate seeds in order to obtain sprouts that have more beneficial dietary properties compared to seeds [1,2,3]
The analysis showed the presence of free (-)-epicatechin (EC), flavones, flavonols, flavonone, and phenolic acids, as well as their esters and glycosides
It can be noted that the application of iron chelate and sodium silicate often caused a reduction in the content of free phenolic compounds in fenugreek and alfalfa sprouts

Summary

Introduction

An alternative method of increasing the nutritional value of food is to germinate seeds in order to obtain sprouts that have more beneficial dietary properties compared to seeds [1,2,3]. Sprouts are recommended by nutritionists due to their high content of bioactive compounds, such as flavonoids, phenolic acids, vitamins, and absorbable minerals [4,5]. These compounds play an important role in protecting the human body from various types of chronic disorders such as cardiovascular disease, diabetes, and cancer [6,7]. The contents of secondary plant metabolites are dependent on stressful growth conditions, such as UV-irradiation, drought, high light, nutrient deficiencies, temperature, and herbicide [10]. An alternative method that effectively increases the accumulation of secondary metabolites (including phenolics) in sprouts is elicitation [11,12,13,14,15,16,17]

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Conclusion