Glucosinolates: Natural Occurrence, Biosynthesis, Accessibility, Isolation, Structures, and Biological Activities

Abstract

Glucosinolates (GSLs) are secondary plant metabolites abundantly found in plant order Brassicales. GSLs are constituted by an S-β-d-glucopyrano unit anomerically connected to O-sulfated (Z)-thiohydroximate moiety. The side-chain of the O-sulfate thiohydroximate moiety, which is derived from a different amino acid, contributes to the diversity of natural GSL, with more than 130 structures identified and validated to this day. Both the structural diversity of GSL and their biological implication in plants have been biochemically studied. Although chemical syntheses of GSL have been devised to give access to these secondary metabolites, direct extraction from biomass remains the conventional method to isolate natural GSL. While intact GSLs are biologically inactive, various products, including isothiocyanates, nitriles, epithionitriles, and cyanides obtained through their hydrolysis of GSLs, exhibit many different biological activities, among which several therapeutic benefits have been suggested. This article reviews natural occurrence, accessibility via chemical, synthetic biochemical pathways of GSL, and the current methodology of extraction, purification, and characterization. Structural information, including the most recent classification of GSL, and their stability and storage conditions will also be discussed. The biological perspective will also be explored to demonstrate the importance of these prominent metabolites.

Influence of Genotype on High Glucosinolate Synthesis Lines of Brassica rapa

“…SFN triggers cytostasis and apoptosis and also detoxifies xenobiotics [ 7 ]. BITC and PEITC have proved to induce apoptosis in cancer cell lines [ 8 , 9 ]. Nitriles have a weaker chemopreventive effect than ITCs [ 7 ].…”

“…Some of the important bioactive compounds are butenyl sulforaphane (SFN), isothiocyanate (BITC) and pentenyl isothiocyanate (PEITC) (Figure 1) [6,7]. The biosynthesis of GSL is one of the more complex processes and more than 130 GSLs have been identified so far [8]. The existence of the different GSL structures is controlled by variability in genes on individual genotypes, especially at loci involved in initial elongation and side-chain modification reactions [9].…”

Optimization of an Extraction Process to Obtain a Food-Grade Sulforaphane-Rich Extract from Broccoli (Brassica oleracea var. italica)

“…Nga [ 16 ] reported that the recovery of glucosinolates from white cabbage in 70% ethanol was around 5.8-fold higher than in water, but it was only 75% of the recovery in methanol. Glucosinolates are usually recovered from plant tissues together with phenolic compounds [ 17 ], then both kinds of molecules have similar behavior in alcohol/water solutions. Do et al [ 18 ] studied the recovery of phenolic compounds from lyophilized L. aromatic in different solvents, reporting recoveries in 75% ethanol and in 75% methanol of around 5-fold higher than recovery in pure water.…”

Sinapic Acid and Sinapate Esters in Brassica: Innate Accumulation, Biosynthesis, Accessibility via Chemical Synthesis or Recovery From Biomass, and Biological Activities

“…Accelerated solvent extraction (ASE) is a technique carried out under high pressure and an inert atmosphere with a range of extraction temperatures from 35 to 200°C. This intensification method has been applied to recover secondary metabolites from Brassica biomass (Mohn et al, 2007;Blažević et al, 2020;Nguyen et al, 2020), including SinA and its derivatives (Li and Guo, 2016;Nandasiri et al, 2019). Aqueous alcoholic extraction of phenolics at high temperature (140-180°C) and high pressure resulted in better extraction yield than conventional method (Nandasiri et al, 2019).…”