NMR, HPLC-ESI-MS, and MALDI-TOF MS Analysis of Condensed Tannins from Delonix regia (Bojer ex Hook.) Raf. and Their Bioactivities

Abstract

The structures of the condensed tannins isolated from leaf, fruit, and stem bark of Delonix regia (Bojer ex Hook.) Raf. have been investigated with (13)C nuclear magnetic resonance ((13)C NMR) and high performance liquid chromatography electrospray ionization mass spectrometry (HPLC-ESI-MS) coupled with thiolysis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analyses. The results showed that these condensed tannins from D. regia possessed structural heterogeneity in monomer units and degree of polymerization. Propelargonidin (PP) and procyanidin (PC) were found in the leaf, fruit, and stem bark of D. regia, while prodelphinidin (PD) was found only in the leaves. The polymer chain lengths of condensed tannins from leaf and fruit organs were detected to be trimers to hexadecamers but from trimers to tridecamers for stem bark. B-type linkages were present in all these compounds. Condensed tannins from different parts of D. regia can be explored as tyrosinase inhibitors and food antioxidants because of their potent antityrosinase and antioxidant activities. The inhibitor concentration leading to 50% enzyme activity (IC(50)) was estimated to be 38 ± 1, 73 ± 2, and 54 ± 1.5 μg/mL for the condensed tannins of leaf, fruit, and stem bark. Condensed tannins extracted from stem bark exhibited the highest antioxidant activity; the DPPH scavenging activity (IC(50)) and the FRAP values were 90 ± 2 μg/mL and 5.42 ± 0.09 mmol AAE/g, respectively.

Proanthocyanidin Characterization and Bioactivity of Extracts from Different Parts of Uncaria tomentosa L. (Cat’s Claw)

“…Some few reports exist in plants, including heteropolymers up to trimers in the leaves of Fagus silvatica [25] and Senna alata [26]. Studies in Rumex acetosa leaves showed predominance 5:1 of procyanidin over the propelargonidin units [27]; and while heteropolymers have been reported in Delonix regia leaves, only procyanidins existed in its bark [28]. In Acacia confuse and Casuarina equisetifolia bark, heteropolymers occurrence has been reported with predominance of procyanidins over propelargonidins [29,30].…”

Condensed Tannins from Ficus virens as Tyrosinase Inhibitors: Structure, Inhibitory Activity and Molecular Mechanism

“…The 13 C NMR spectra of the condensed tannins were recorded on a Varian Mercury-600 spectrometer (Palo Alto, CA, USA) at 150 MHz as described in reference [31].…”

Determination of Antioxidant Compounds in Foodstuff

“…Several studies describe the use of NMR in the identification of diff fi erent ff ff compounds present in natural matrices: epimeric forms of fl avone glycosides fl [219]; tannin isomers [220]; anthocyanins [221]; rosmarinic acid [222]; para-hydroxy methyl benzoate glucoside, cycloeucalenol cis-ferulate, cycloeucalenol trans-ferulate, trans-ferulic acid, trans-ferulic acid methyl ester, cis-ferulic acid, cis-ferulic acid methyl ester, methyl caffeate, vanillic ff ff aldehyde and para-hydroxy benzaldehyde [223]; 9-O-(3-carboxymethyl-4-(p-formylstyryl))hydroxybutanoic acid, 2-hydroxy-3-methoxycaffeic ff ff acid 5-O-β-D-glucopyranoside and 3 -O-methyl-4 -O-(4-O-galloyl-α-Lrhamnopyranosyl) ellagic acid [224].…”