Hydrolyzable Tannins of Tamaricaceous Plants. V. Structures of Monomeric–Trimeric Tannins and Cytotoxicity of Macrocyclic-Type Tannins Isolated from Tamarix nilotica

Abstract

Three new ellagitannin monomers, nilotinins M5-M7 (1-3), a dimer, nilotinin D10 (4), and a trimer, nilotinin T1 (5), together with three known dimers, hirtellin D (7) and tamarixinins B (8) and C (9), and a trimer, hirtellin T2 (6), were isolated from Tamarix nilotica dried leaves. The structures of the tannins were elucidated by intensive spectroscopic methods and chemical conversions into known tannins. The new trimer (5) is a unique macrocyclic type whose monomeric units are linked together by an isodehydrodigalloyl and two dehydrodigalloyl moieties. Additionally, dimeric and trimeric macrocyclic-type tannins isolated from T. nilotica in this study were assessed for possible cytotoxic activity against four human tumor cell lines. Tumor-selective cytotoxicities of the tested compounds were higher than those of synthetic and natural potent cytotoxic compounds, including polyphenols, and comparable with those of 5-fluorouracil and melphalan.

Ellagitannins, gallotannins, and gallo-ellagitannins from the galls of Tamarix aphylla

“…However, such attachment mode has not been observed in any of the hydrolyzable tannins isolated from other tamaricaceous plants, including those in our investigation of the constituents of Tamarix species [15], or in those isolated from plants of the genus Reaumuria, e.g., Reaumuria hirtella [17] or in vermiculatin (5) recently isolated from Reaumuria vermiculata [9] (Fig. 1).…”

“…In our recent investigations on the hydrolyzable tannins of Tamarix nilotica and Tamarix tetrandra, we have reported several monomericoligomeric hydrolyzable tannins, which were collectively referred to as tamaricaceous hydrolyzable tannins [15]. Hydrolyzable tannins isolated from these Tamarix species showed potent cytotoxicity with elevated tumor specificity, which was largely dependent on the structure [15a), c)].…”

“…Hydrolyzable tannins isolated from these Tamarix species showed potent cytotoxicity with elevated tumor specificity, which was largely dependent on the structure [15a), c)]. Structurally, among the hydrolyzable tannins isolated in our previous studies [15], the representative attachment of the acyl moieties produced biogenetically by C-O oxidative coupling between two galloyl units [DHDG (1, m-GOG) and isoDHDG (2, p-GOG)] or three galloyl units [hellinoyl (3, m-GO-m-GOG)] to the glucose core are in a mode in which the galloyl ring bearing a single hydrogen is attached to O-2 of the glucose core, whereas the galloyl ring bearing two hydrogens is attached to O-1 of the glucose core [15].…”

Tamarix nilotica (Ehrenb) Bunge: A Review of Phytochemistry and Pharmacology

“…The review of literature reported the isolation of monomeric (Isohirtellin C, Remurin A-B, Gemin D, Nilotinin, Nilotinin M2-7, Hippomanin A, and Tellimagrandin I-II), dimeric (Nilotinins D1-D10, Tamarixinin A-C and Hirtellin A-D and F), trimeric (Nilotinin T1-T2, Hirtellin T1-T3) and tetrameric ellagitannins (Nilotinin Q1) from the aqueous acetone extracts of leaves of T. nilotica growing in Egypt [10,[34][35][36][37]. Interest in the ellagitannin constituents due to their marked antiviral, antimicrobial, immunomodulatory, antitumor, and hepatic protective activities, which are largely dependent on the tannin structures [38] (Figure 3).…”

“…Ellagitannins from the leaves of T. nilotica grown in Egypt were reported to exhibit significant host-mediated antitumor activities against sarcoma-180 in mice and strong cytotoxic effects with higher tumor specificity against four tumor cell lines [35,37]. T. nilotica showed a selective cytotoxic potential against liver (HUH-7), colon (HCT-116), lung and breast (MCF-7) carcinoma cell, while being non-toxic to other cancer cells [9,40].…”