Phenolic Antioxidants (Hydrolyzable Tannins, Flavonols, and Anthocyanins) Identified by LC-ESI-MS and MALDI-QIT-TOF MS from Rosa chinensis Flowers

Abstract

Rosa chinensis (Yuejihua) is a well-known ornamental plant, and its flowers are commonly used in traditional Chinese medicine. Methanolic crude extracts of dried R. chinensis flowers were used for simultaneous determination of phenolic constituents by liquid chromatography-mass spectrometry (LC-MS) and matrix-assisted laser desorption/ionization quadrupole ion trap time-of-flight mass spectrometry (MALDI-QIT-TOF MS). A total of 36 known and unknown phenolics were identified as hydrolyzable tannins, flavonols, and anthocyanins, mainly including gallotannins (mono-, di-, or trigalloylglucopyranosides), ellagitannins, quercetin, quercetin/kaempferol mono- and diglycosides, and cyanidin/pelargonidin diglycosides. MALDI-QIT-TOF MS was applied not only to verify most phenolics isolated and identified by LC-MS but also to tentatively identify two ellagitannins (rugosins B and C) not isolated and unidentified by LC-MS. This study is the first to demonstrate the rapid and successful use of MALDI-QIT-TOF MS and LC-MS to directly and simultaneously identify phenolics in the crude extracts of R. chinensis flowers without any purification. The antioxidant activity of the crude extracts from R. chinensis flowers was also measured with three assay methods. The results showed that the phenolic antioxidants from R. chinensis flowers exhibited very strong radical scavenging effect and antioxidant power. High levels of flavonols and hydrolyzable tannins might be important bioactive principles in the dried R. chinensis flowers.

Identification of phenolic compounds from pomegranate (Punica granatum L.) seed residues and investigation into their antioxidant capacities by HPLC–ABTS+ assay

“…Compounds 2, 5, 10, 12, 14 performing maximum UV absorbance in the range of 255-280 nm, was in agreement with the identification of hydrolysable tannin from Rosa chinensis flowers (Cai, Xing, Sun, Zhan, & Corke, 2005). Compound 5 could be pendunculagin (Bis-2, 3; 4, 6-O-hexahydroxydiphenoylglucose) with [M-H] − ion at m/z 783 consisted of two HHDP (Hexahydroxydiphenoyl) groups (302 unit per group) and one glucosyl group (180 unit) (Tian, Li, Ji, Zhang, & Luo, 2009;Salminen, Ossipov, Loponen, Haukioja, & Pihlaja, 1999) Table 2.…”

Determination of antioxidant activity in free and hydrolyzed fractions of millet grains and characterization of their phenolic profiles by HPLC-DAD-ESI-MSn

“…Similarly, peaks 46 and 48 were tentatively identified as a kaempherol hexoside and a quercetin-O-pentoside, respectively. The MS 3 analysis of peak 46 showed that deprotonated base ion of the glycoside at m/z 447 with maximum absorbance at 255 and 350 nm and the ion at m/z 285 corresponding to the deprotonated aglycone of kaempherol (Cai, Xing, Sun, Zhan, & Corke, 2005). Since glucose is the most common sugar present, peak 46 was suggested to be kaempherol 3-O-glucoside (Cuyckens & Claeys, 2004).…”

Isoliquiritigenin (4,2′,4′-trihydroxychalcone): A new matrix-assisted laser desorption/ionization matrix with outstanding properties for the analysis of neutral oligosaccharides

“…Flavonols in the crude extract of the dried Rose chinensis flowers have been identified by MALDI-TOF MS without using any matrix [30]. Recently, flavonoids -quercetin and rutin -have been used as new matrices for MALDI-TOF-MS analysis of Pt(II) and Pd(II) complexes [31].…”