Synthesis and cytotoxicity of lupane-type triterpenoid glyceryl esters

A new series of betulinic acid and betulin derivatives were synthesized by introducing a D-glycerol moiety at the C-3 and/or C-28 positions of the lupane skeleton. The resulting glyceryl esters were evaluated in vitro for their cytotoxic activity against A549, DLD-1 and WS1 human cell lines. The structure-activity relationships study revealed that the incorporation of a glycerol unit at the C-3 or C-28 position of the lupane core resulted in compounds exhibiting potent cytotoxic activity together with decreased liposolubility.     

Plant triterpenoid saponins: biosynthesis,in vitro production,and pharmacological relevance

Protoplasma - The saponins are a diverse class of natural products, with a broad scale distribution across different plant species. Chemically characterized as triterpenoid glycosides, they posses...     

Synthesis and cytotoxic activity of the N-acetylglucosamine-bearing triterpenoid saponins

Fourteen ursolic acid and oleanolic acid saponins with N-acetyl-β-d-glucosamine, and (1→4)-linked and (1→6)-linked N-acetyl-β-d-glucosamine oligosaccharide residues were synthesized in a convergent manner. The structures of all compounds were confirmed by ¹H NMR and ¹³C NMR spectroscopy and by mass spectrometry, and their cytotoxic activities were assayed in three cancer cell lines. Only oleanolic acid-3-yl β-d-GluNAc showed significant cytotoxicity against HL-60 and BGC-823.     

New triterpenoid saponins from cacti and anti-type I allergy activity of saponins from cactus

The research in our laboratory focuses on the isolation of saponins from cactus. In this study, we report five new triterpenoid saponins, dumortierinoside A methyl ester (1), pachanoside I1 (2), pachanoside D1 (3), gummososide A (4), and gummososide A methyl ester (5). Compounds 1-3 isolated from Isolatocereus dumortieri Backbg., and compounds 4 and 5 were isolated from Stenocereus alamosensis A. C. Gibson & K. E. Horak. Compound 2 possessed a new pachanane-type triterpene skeleton, pachanol I, in its aglycon. The aglycon of 3 was pachanol D, while those of 4 and 5 were both gummosogenin, which we have previously reported, but this is the first report of pachanol D and gummosogenin in their aglycon forms. Additionally, we evaluated the anti-type I allergy activity of the saponins with RBL-2H3 (Rat basophilic leukemia) cells by measuring the β-hexosaminidase release inhibitory activity. As a result of these studies, gummososide A methyl ester (5) was found to show activity (IC(50)=99.5 μM) and thurberoside A exhibited mild activity (IC(50)=166.9 μM).     

Pentacyclic triterpenoid and saponins from Gambeya boukokoensis

Chemical studies of the EtOAc extract of Gambeya boukokoensis Aubr. et Pellegr. stem bark led to the isolation of eight compounds. Three of them were elucidated as new compounds and designated as: gamboukokoensein A, 1alpha,2alpha,3beta,19alpha,23-pentahydroxyurs-12-en-28-oic acid; gamboukokoenside A, 2beta,3beta,6beta,28-tetrahydroxyolean-12-en-23-oic acid 23-O-alpha-L-arabinopyranosyl ester and gamboukokoenside B, 6beta,28-dihydroxy-3-oxoolean-12-en-23-oic acid 23-O-alpha-L-arabinopyranosyl ester. The other five compounds were known and identified as myrianthic acid, protobassic acid, oleanolic acid, erythrodiol and chondrillasterol. Their structures were elucidated on the basis of one and two dimensional NMR spectroscopic techniques, FABMS, ESMS and chemical evidence.     

Pro-apoptotic activity of acylated triterpenoid saponins from the stem bark of Albizia chevalieri harms

As a continuation of our interest in apoptosis-inducing triterpenoid saponins from Albizia genus, phytochemical investigation of the stem bark of Albizia chevalieri led to the isolation of three new oleanane-type saponins, named chevalierosides A–C (1–3). Their structures were established on the basis of extensive analysis of 1D and 2D NMR (¹H-, ¹³C NMR, DEPT, COSY, TOCSY, ROESY, HSQC and HMBC) experiments, HRESIMS studies, and by chemical evidence. The pro-apoptotic effect of the three saponins was evaluated on two human cell lines (pancreatic carcinoma AsPC-1 and hematopoietic monocytic THP-1). Cytometric analyses showed that saponins 1–3 induced apoptosis of both human cell lines (AsPC-1 and THP-1) in a dose-dependent manner.     

New triterpenoid saponins with strong alpha-glucosidase inhibitory activity from the roots of Gypsophila oldhamiana

Seven new triterpenoid saponins (1-7), have been isolated and elucidated from the roots of Gypsophila oldhamiana together with five known triterpenoid saponins (8-12). These saponins which could be classified into three series: 3-O-monoglucosides (1, 8, 9), 28-O-monoglucosides (2-4, 12) and 3, 28-O-bidesmosides (5-7, 10, 11), have been evaluated for their alpha-glucosidase inhibition activity. As a result, the preliminary structure-activity relationships were discussed based on the position of sugar linkage attached to the aglycone, and 28-O-monoglucosides 2-4 and 12 showed significant inhibitory activities on alpha-glucosidase.     

Synthesis and antitumor activity of two natural N-acetylglucosamine-bearing triterpenoid saponins: lotoidoside D and E

Two natural triterpenoid saponins bearing N-acetylglucosamine, lotoidoside D and lotoidoside E, which had been available only from Glinus lotoides growing in Egyptian desert, were facilely synthesized from readily available oleanolic acid. Preliminary pharmacological research showed their antitumor activity against HeLa cell.     

Molecular activities, biosynthesis and evolution of triterpenoid saponins

Saponins are bioactive compounds generally considered to be produced by plants to counteract pathogens and herbivores. Besides their role in plant defense, saponins are of growing interest for drug research as they are active constituents of several folk medicines and provide valuable pharmacological properties. Accordingly, much effort has been put into unraveling the modes of action of saponins, as well as in exploration of their potential for industrial processes and pharmacology. However, the exploitation of saponins for bioengineering crop plants with improved resistances against pests as well as circumvention of laborious and uneconomical extraction procedures for industrial production from plants is hampered by the lack of knowledge and availability of genes in saponin biosynthesis. Although the ability to produce saponins is rather widespread among plants, a complete synthetic pathway has not been elucidated in any single species. Current conceptions consider saponins to be derived from intermediates of the phytosterol pathway, and predominantly enzymes belonging to the multigene families of oxidosqualene cyclases (OSCs), cytochromes P450 (P450s) and family 1 UDP-glycosyltransferases (UGTs) are thought to be involved in their biosynthesis. Formation of unique structural features involves additional biosynthetical enzymes of diverse phylogenetic background. As an example of this, a serine carboxypeptidase-like acyltransferase (SCPL) was recently found to be involved in synthesis of triterpenoid saponins in oats. However, the total number of identified genes in saponin biosynthesis remains low as the complexity and diversity of these multigene families impede gene discovery based on sequence analysis and phylogeny.This review summarizes current knowledge of triterpenoid saponin biosynthesis in plants, molecular activities, evolutionary aspects and perspectives for further gene discovery.     

Oligosaccharide polyester and triterpenoid saponins from the roots of Polygala japonica

An oligosaccharide polyester, 1-O-(E)-p-coumaroyl-(3-O-benzoyl)-beta-D-fructofuranosyl-(2-->1)-[6-O-(E)-feruloyl-beta-D-glucopyranosyl-(1-->2)]-[6-O-acetyl-beta-D-glucopyranosyl-(1-->3)-(4-O-acetyl)-beta-D-glucopyranosyl-(1-->3)]-4-O-[4-O-alpha-L-rhamnopyranosyl-(E)-p-coumaroyl]-alpha-D-glucopyranoside (polygalajaponicose I), and four triterpenoid saponins, 3beta, 23, 27-trihydroxy-29-O-beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl-olean-12-en-28-oic acid (polygalasaponin XLVII), 3-O-beta-D-glucopyranosyl presenegenin 28-O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-fucopyranosyl ester (polygalasaponin XLVIII), 3-O-beta-D-glucopyranosyl presenegenin 28-O-beta-D-galactopyranosyl-(1-->5)-beta-D-apiofuranosyl-(1-->4)-beta-D-xylopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranosyl ester (polygalasaponin XLIX) and 2beta, 27-dihydroxy-3-O-beta-D-glucopyranosyl 11-oxo-olean-12-en-23, 28-dioic acid 28-O-beta-D-galactopyranosyl-(1-->5)-beta-D-apiofuranosyl-(1-->4)-beta-D-xylopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-fucopyranosyl ester (polygalasaponin L), in addition to five known compounds have been isolated from the roots of Polygala japonica.     

Assamicin I and II, novel triterpenoid saponins with insulin-like activity from Aesculus assamica Griff

Two novel triterpenoid saponins with insulin-like activity, termed assamicin I and II, were isolated from the roots of Aesculus assamica Griff. and their structures were characterized as 1 and 2, respectively. They inhibited release of free fatty acids from epinephrine-treated rat adipocytes and enhanced glucose uptake into 3T3-L1 adipocytes.     

New triterpenoid saponins from the roots of Gypsophila perfoliata Linn

Nine new triterpenoid saponins (1–9) have been isolated from the roots of Gypsophila perfoliata Linn. Their structures were established on the basis of extensive NMR (¹H, ¹³C, HSQC and HMBC) and ESIMS studies.     

Bioactive triterpenoid saponins and phenolic compounds against glioma cells

A total of 54 natural origin compounds were evaluated for their activity in inhibiting the proliferation of glioma cells. Results showed that four Aesculus polyhydroxylated triterpenoid saponins (3–6), six Gleditsia triterpenoid saponins (7–12), and five phenolic compounds (43–46, 51) had dose-dependent activity suppressing the proliferation of both C6 and U251 cells. Structure–activity relationship analysis suggested that the acetyl group at C-28 for the Aesculus saponins and the monoterpenic acid moiety for the Gleditsia saponins could be critical for the activity of these active compounds. Aesculioside H (4), gleditsioside A (7), and feuric acid 3,4-dihydroxyphenethyl ester (FADPE, 46) were the three most active compounds from the different types of the active compounds and induced apoptosis and necrosis in glioma cells.     

Cytotoxic triterpenoid saponins from the fruits of Aesculus pavia L

Continued chemical investigation on the fruits of North American Aesculus pavia L. resulted in the isolation and identification of 13 polyhydroxyoleanene pentacyclic triterpenoid saponins, named aesculiosides IIe-IIk (1-7), and IIIa-IIIf (8-13), together with 18 known compounds: aesculiosides Ia-Ie (14-18), IIa-IId (19-22), IVa-IVc (23-25), 3-O-[beta-D-galactopyranosyl(1-->2)]-alpha-L-arabinofuranosyl(1-->3)-beta-D-glucuronopyranosyl-21,22-O-diangeloyl-3beta,15 alpha,16 alpha,21 beta,22 alpha,28-hexahydroxyolean-12-ene (26), 3-O-[beta-D-glucopyranosyl(1-->2)]-alpha-L-arabinofuranosyl(1-->3)-beta-D-glucuronopyranosyl-21,22-O-diangeloyl-3beta,16 alpha,21 beta,22 alpha,24 beta,28-hexahydroxyolean-12-ene (27), 3-O-[beta-D-galactopyranosyl(1-->2)]-alpha-L-arabinofuranosyl(1-->3)-beta-D-glucuronopyranosyl-21,22-O-diangeloyl-3beta,16 alpha,21 beta,22 alpha,28-pentahydroxyolean-12-ene (28), R(1)-barrigenol (29), scopolin (30), and 5-methoxyscopolin (31). The structures of these compounds were elucidated by spectroscopic and chemical analyses. Compounds 14-22 and 26-28 were tested in vitro for their activity against 59 cell lines from nine different human cancers including leukemia, non-small cell lung, colon, CNS, melanoma, ovarian, renal, prostate, and breast. It was found that compounds with two-acyl groups at C-21 and C-22 had cytotoxic activity for all cell lines tested with GI(50) 0.175-8.71 microM, while compounds without acyl groups at C-21 and C-22 had weak or no cytotoxic activity. These results suggest that the acyl groups at C-21 and C-22 are essential for their activity.     

Synthesis and structure-activity relationship study of cytotoxic germanicane- and lupane-type 3beta-O-monodesmosidic saponins starting from betulin

Germanicane-type triterpenes allobetulin (3) and 28-oxoallobetulin (4) can be obtained by the Wagner-Meerwein rearrangement of the more available lupane-type triterpenes betulin (1) and betulinic acid (2), respectively. The medical uses of betulinic acid (2) and its derivatives are limited because of their poor hydrosolubility and pharmacokinetics properties. In order to overcome this major problem, we synthesized and studied the in vitro anticancer activity of a series of 3beta-O-monodesmosidic saponins derived from betulin (14-16), betulinic acid (20-22), allobetulin (23-28) and 28-oxoallobetulin (29-34) based on six different natural sugar residues (d-glucose, l-rhamnose, d-arabinose, d-galactose, d-mannose and d-xylose). This structure-activity relationship study confirmed that betulinic acid saponins are generally better in vitro anticancer agents than those derived from betulin with the exception of betulin 3beta-O-alpha-d-mannopyranoside (15) which exerted a potent cytotoxic activity against lung carcinoma (A-549) and colorectal adenocarcinoma (DLD-1) human cell lines with IC(50) ranging from 7.3 to 10.1mumol/L. Furthermore, although the synthesis of novel germanicane-type saponins was carried out with success, the bioactivity measured for these glycosides was not as high as we anticipated since only the 3beta-O-beta-d-glucopyranoside and 3beta-O-beta-d-galactopyranoside of allobetulin (23,24) showed moderate anticancer activity (IC(50) 30-40 micromol/L).     

Triterpenoids and triterpenoid saponins from the aerial parts of Fagonia indica Burm

As part of our search of new bioactive compounds from indigenous medicinal plants, phytochemical investigation of the aerial parts of Fagonia indica Burm led to the isolation of seven compounds including two new compounds, namely, indicacin (1) and fagonicin (2), and five known compounds (3–7) from the methanol extract. Compounds 6 and 7 are hitherto unreported from this plant. The structures of the new compounds were elucidated from their spectral data, mainly HREIMS, 1D NMR (¹H, ¹³C NMR, and DEPT) and 2D NMR (COSY, NOESY, HSQC and HMBC), and by comparison with the literature data. The new compounds 1 and 2 were assayed for their cytotoxicity against human colorectal cancer cell line H-29. Compound 1 exhibited 51.40% cytotoxicity at 6.25 μM/mL dose whereas compound 2 demonstrated 39.3% cytotoxicity at the same dose.     

Esters of new oleanane-type triterpenoid saponins from Schefflera kwangsiensis

Eleven new oleanane-type triterpenoid saponins were isolated from the aerial parts of Schefflera kwangsiensis (1–11), together with nine esters (12–20) of known saponins. The structures of these compounds were elucidated on the basis of spectroscopic data analysis and chemical evidence. Furthermore, in in vitro assays, compounds 2, 3, 5, 7, 8, 11–13, 15, 17 and 18 (10 μM) exhibited moderate hepatoprotective activity against d-galactosamine-induced HL-7702 cell damage.     

Evaluation of novel antioxidant triterpenoid saponins from the halophyte Salicornia herbacea

As a part of an ongoing search for novel antioxidants from the salt marsh plants, bioactivity-isolation and structure determination of constituents from Salicornia herbacea were performed. One new triterpenoid saponin (4), along with three known saponins (1-3), has been isolated from n-BuOH fraction of S. herbacea. On the basis of the spectroscopic methods, the structure of the new saponin 4 was elucidated as 3β-hydroxy-23-oxo-30-noroleana-12, 20(29)-diene-28-oic acid 3-O-β-D-glucuronopyranosyl-28-O-β-d-glucopyranoside. Scavenging effects of saponins 1-4 were examined on 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical and peroxynitrite. Particularly, saponin 3 exerted significant antioxidant activity on both authentic peroxynitrite and peroxynitrite generated from morpholinosydnonimine (SIN-1).     

Synthesis of lupane-type saponins bearing mannosyl and 3,6-branched trimannosyl residues and their evaluation as anticancer agents

The saponins modified with mono- or trimannosyl residues can provide a convenient means of delivering drugs to certain human cells via interactions with mannose receptors. In the study reported therein, we developed a convenient approach for the synthesis of 3-O-mannoside and branched trimannoside derivatives of the saponin lupeol and of C-28 acyl esters of 3-O-acetyl-betulinic acid bearing the same mannosyl entities. Lupeol and 3-O-acetyl-betulinic acid were mannosylated with tetra-O-benzoyl- or tetra-O-acetyl-alpha-D-mannopyranosyl trichloroacetimidates. De-esterification followed by regioselective dimannosylation of the unprotected monosaccharide derivatives with 2equiv of tetra-O-benzoyl-alpha-D-mannopyranosyl trichloroacetimidate selectively yielded O-3,O-6-linked trimannosides. The cytotoxic activity of selected lupane-type saponins (derivatives of lupeol, betulinic acid, and betulin) toward normal human fibroblasts and various cancer cell lines was also compared.     

Arvensoside A and B,triterpenoid saponins from Calendula arvensis

Two new triterpenoid glycosides from the aerial parts of Calendula arvensis were identified as oleanolic acid-28-O-β-D-glucopyranoside-3-β-O-(O-β-D-galactopyranosyl(1 → 3)-β-D-glucopyranoside) and oleanolic acid 3-β-O-(O-β-D-galactopyranosyl(1 → 3)-β-D-glucopyranoside) by FAB, FAB MIKE mass spectrometry and ¹³C NMR spectroscopy.