MALDI-TOF MS Analysis of Isoflavones in Soy Products

Abstract

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a new technique having a number of advantages for food analysis. This study is the first to demonstrate the use of MALDI-TOF MS to identify isoflavones in soy samples. 2',4',6'-Trihydroxyacetophenone (THAP) and 2,5-dihydroxybenzoic acid (DHB) were both good matrices for isoflavones, but DHB was chosen as the best because it worked well for sample extracts, with good spot-to-spot repeatability. Isoflavones were predominantly ionized in a protonated form with a very small amount of sodium or potassium adduct ions. Fragmentation occurred only through loss of glycosidic residues. Daidzin showed more than twice the response of genistin using MALDI-TOF MS. A simple solid phase extraction of isoflavones from soy samples was developed for MALDI-TOF MS analysis. MALDI-TOF MS can provide an isoflavone profile in 2 min and serves as a powerful tool to identify and study processing changes of isoflavones in soy products.

Effects of a surface topography composite with puerariae radix on human STRO-1-positive stem cells

“…The preparation of DHB and sample was modified from (38): the matrix solution contained 10−15 mg/mL DHB in 10% ethanol. The ratio of matrix solution to clude extracts was 1:1.…”

Analysis of carbohydrates and glycoconjugates by matrix‐assisted laser desorption/ionization mass spectrometry: An update covering the period 1999–2000

“…It was used to study flavonols from yellow onion (Allium cepa L.) and green tea. DHB, on the other hand was preferred for the analysis of isoflavones; this matrix gave predominantly [M þ H] þ ions with some fragmentation due to the loss of glycosidic residues (Wang & Sporns, 2000b).…”

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“…Initially, PSD was applied in peptides [131,132] and carbohydrate sequencing [133], and currently, there are some applications in natural products studies. It was used to identify saponins [134], flavonoids [122], isoflavones [135], carotenoids [136], and hydrolysable and condensed tannins [66,137] as well as to examine triacylglycerols and phosphatidylethanolamines from plants, algae, and animal tissue [138][139][140]. Different carotenes (polyenes without oxygen) and xanthophylls (polyenes with oxygen) were analyzed by MALDI and produced radical ions (molecular ions) through the removal (M •+ ) of one electron (l " Fig.…”

“…The O-glycosylated isoflavones from soy [Glycine max L. (Fabaceae)] showed fragments with structural importance by PSD, including the main fragment that occurs through the loss of sugars, which is similar to ESI. In addition, the DHB and THAP matrices were evaluated, and DHB showed better ionization results and a higher number of fragments in MS/MS spectra [135]. PSD was also applied in the study of peracetylated isoflavone glycosides from their protonated and cationized different metal ions to understand the gas phase molecule cluster complexes.…”