Structures, NMR Spectroscopic Features, and Cytotoxic Properties of Oligomeric Hellinoyl (m-GO-m-GOG)-Type Ellagitannins from the Galls of Tamarix aphylla

Abstract

Ellagitannin oligomers are large molecules habitually showing complex NMR spectra that are sometimes misinterpreted and lead to incorrect structures. Understanding the NMR spectroscopic features of a group of ellagitannins would overcome these inadequacies. In this study, investigation of the galls of Tamarix aphylla led to the isolation of three new ellagitannin oligomers, phyllagallins T1 (1), T2 (2), and Q1 (3), a known monomer nilotinin M4 (4), four known dimers, nilotinins D7 (5) and D8 (6), hirtellin B (7), and tamarixinin A (8), and a simple phenolic, dehydrotrigallic acid (9). 1D and 2D NMR, HRESI-TOFMS, and ECD experiments show that compounds 1−8 are hellinoyl-type ellagitannins. The NMR spectroscopic features of this type of ellagitannins and the reasons for the abnormal upfield shifts of glucose anomeric proton and hellinoyl moiety proton signals are established considering the experimental results as well as quantum chemical calculation on a simple hellinoyl-type monomer, phyllagallin M2. Based on these results, the NMR assignments reported previously by a different research group for bracteatinin T 1 and hirtellin T 3 are revised. A cytotoxicity study against human oral squamous cell carcinoma cell lines (Ca9-22, HSC-2, and HSC-4) and human mesenchymal normal oral cells (HGF, HPC, and HPLF) showed cytotoxic effects with tumorspecificity higher than 5.2, 3.0, 1.6, and 2.0 for compounds 5, 2, 9, and 3, respectively.

New Megastigmane and Polyphenolic Components of Henna Leaves and Their Tumor-Specific Cytotoxicity on Human Oral Squamous Carcinoma Cell Lines

“…The 1 H NMR spectrum of 1 (Figures S3-S5) displayed spectroscopic features typical of a galloyl moiety [22]; an aromatic 2H singlet (δ H 7.13, H-2 /H-6 ) that exhibits HSQC correlation with a non-oxygenated aromatic carbon (δ C 109.6, 2C, C-2 /C-6 ) and HMBC correlations with oxygenated aromatic carbon (δ C 146, 2C, C-3 /C-5 , and δ C 137.7, C-4 ), a quaternary aromatic carbon (δ C 120.5, C-1 ), and a carbonyl carbon (δ C 167.2, C-7 ). The 1 H NMR and 1 H-1 H COSY spectra of 1 (Table 1, Figures S6-S8) exhibited a resonating system of seven aliphatic proton spins at δ H 4.49-3.19 (Table 1), with a large coupling pattern of the glucose H-2 -H-5 (J H-1 -H-2 = 7.8, J H-2 -H-3 = J H-3 -H-4 = J H-4 -H-5 = 9.6 Hz), highlighting the 4 C 1 conformation of the glucopyranose moiety [23]. A large coupling constant of the glucose H-1 proton signal (δ H 4.49, J = 7.8 Hz) indicates the β-configuration of the glucose's anomeric center [22].…”

Dietary Polyphenols as Prospective Natural-Compound Depression Treatment from the Perspective of Intestinal Microbiota Regulation

“…Dietary polyphenols used to modulate microglial activation require gut microbiota activity to produce appropriate bioactive metabolites for the treatment of depressive symptoms. The ellagitannin-like polyphenols in pomegranate extract are poorly absorbed in the small intestine and have low bioavailability [ 113 ], and, upon reaching the colon, are biotransformed by the gut microbiota to produce the bioactive compound urolithin ( 6H-dibenzo[b, d]pyran-6-one derivatives ). Urolithin reduces microgliosis and amyloid-beta plaque deposition [ 114 ], reduces anxiety-like behaviors, and improves memory [ 115 ].…”

Design, Characterization, and Antimicrobial Evaluation of Copper Nanoparticles Utilizing Tamarixinin a Ellagitannin from Galls of Tamarix aphylla

“…In our preceding research publications, tannin-rich plant sources including galls of T. aphylla were deciphered [15] which yields approximately 71% total extract, with hydrolyzable tannins accounting for the majority [15,16]. The highest occurring type of ellagitannins in the galls of T. aphylla, according to our previous research, are those having a sugar core with a free hydroxyl group at the C-1 position, wherein the ellagitannin tamarixinin A (TA) is the most prevalent one [17]. TA is an ellagitannin dimer (Figure 1) with a wide range of reducing functionalities (OH, CO, and C-O-C), making it an excellent agent for reducing copper ions to metal CuNPs.…”