Correlation of Glucosinolate Content to Myrosinase Activity in Horseradish (Armoracia rusticana)

Abstract

Fully developed horseradish (Armoracia rusticana Gaertn., Mey., & Scherb.) roots from 27 accessions and leaves from a subset of 9 accessions were evaluated for glucosinolates and myrosinase enzyme activity. Eight different glucosinolates were detected (based on HPLC retention times as desulfoglucosinolates) in both root and leaf tissues. The sum of these glucosinolates, referred to as total, ranged from 2 to 296 micromol g(-1) of dry weight (DW) in both tissues. Four glucosinolates (sinigrin, glucobrassicin, neoglucobrassicin, and gluconasturtiin) were detected in major quantities. In fully developed roots, sinigrin concentration represented approximately 83%, gluconasturtiin approximately 11%, and glucobrassicin approximately 1% of the total glucosinolates. Approximately the same proportions of individual glucosinolates appeared in fully developed leaves, except that glucobrassicin was substituted by neoglucobrassicin and gluconasturtiin concentration was significantly lower (<1%). At least four other glucosinolates were detected in very small quantities (<1%) in both roots and leaves. Myrosinase (beta-thioglucoside glucohydrolase, EC 3.2.3.1) is the enzyme responsible for the hydrolysis of the parent glucosinolates into biologically active products. Very little is known about myrosinase activity and the correlation of its activity to total and individual glucosinolates in plant tissues. Significant differences in myrosinase activity were detected between the roots and leaves, ranging from 1.2 to 57.1 units g(-1) of DW. Data showed no correlation between myrosinase activity and total and/or individual glucosinolates in the roots. However, in the leaves, significant correlations were found between myrosinase activity and total glucosinolates (0.78 at P = 0.01) and between myrosinase activity and sinigrin (0.80 at P = 0.01). Glucosinolates content and myrosinase activity were also correlated in young and fully developed roots and leaves and during tissue crushing. Glucobrassicin concentration in the roots and neoglucobrassicin concentration in the leaves were significantly higher in young than in fully developed tissue. Crushing of the tissue resulted in rapid hydrolysis of sinigrin and glucobrassicin, as expected, from the presence of myrosinase. Likewise, myrosinase activity declined rapidly after crushing, perhaps due to inactivation by the reaction products and/or the depletion of its substrates.

Evaluation of Seasonal Variations in the Glucosinolate Content in Leaves and Roots of Four European Horseradish (Armoracia rusticana) Landraces

“…GLS can be divided into aliphatic, aralkyl and indole group. Horseradish is one of the richest sources of GLS [Fahey et al, 2001;Li & Kushad, 2004;Agneta et al, 2012Agneta et al, , 2014Alsnour, 2013]. Seventeen GLS have been identifi ed in horseradish to date [Agneta et al, 2014].…”

“…Differences in GLS profi les and content were observed between horseradish accessions and between plant organs. According to Li & Kushad [2004], the total GLS content in the roots of 27 horseradish accessions and the leaves of 9 accessions ranged from 2 to 296 μmol/g DW and from 34 to 201 μmol/g DW, respectively. The noted variations could also be attributed to the growth stage [Li & Kushad, 2004;Alnsour, 2013].…”

“…According to Li & Kushad [2004], the total GLS content in the roots of 27 horseradish accessions and the leaves of 9 accessions ranged from 2 to 296 μmol/g DW and from 34 to 201 μmol/g DW, respectively. The noted variations could also be attributed to the growth stage [Li & Kushad, 2004;Alnsour, 2013]. It is assumed that younger tissues are a richer source of indole GLS than senescent tissues [Mevy et al, 1997].…”

“…The knowledge about the composition, content and distribution of GLS in different organs of horseradish plants is limited [Li & Kushad, 2004;Agneta et al, 2014]. Various authors have recognized the need to examine GLS concentrations in intermediate periods of horseradish development [Agneta et al, 2014].…”

Handbook of Plant Food Phytochemicals

“…capitata) [76], 60 oilseed rape varieties (B. napus var. oleifera) [36] and 27 horseradish varieties (Amoracia rusticana) [93] likewise showed a wide range of glucosinolate levels between different accessions of these crops. Similar variation was found in an evaluation of antioxidant compounds, vitamin C, 1 -carotene, lutein, a -tocopherol and total phenolics in a range of cabbage, cauliflower, Brussels sprout, Chinese cabbage and broccoli cultivars grown under uniform cultural conditions [160].…”