Oleanolic acid and hederagenin glycosides from Weigela stelzneri

A Comprehensive Study on the Chemical Characterization and Neuroprotective Evaluation of Pracaxi Nuts Extracts Obtained by a Sustainable Approach

The Amazonian Pentaclethra macroloba (Willd.) Kuntze nuts contain a lipidic fraction with health-promoting effects, but little is known about the bioactivity of other constituents. In this study, the lipidic fraction obtained using supercritical fluid extraction (SFE) with CO2 was chemically characterized by using lipidomics techniques. The SFE-CO2 residue, named as pracaxi cake, was re-extracted by pressurized liquid extraction following a biorefinery approach. Using a response surface methodology and based on the extraction yield and different in vitro assays, two optimum conditions were obtained: 80% and 12.5% of ethanol at 180 °C. Under these conditions, extraction yield and different in vitro measurements related to neuroprotection were assessed. Chemical characterization of these extracts suggested the presence of triterpenoid saponins and spermidine phenolamides, which were not previously reported in pracaxi nuts. These results suggest that pracaxi oil extraction by-products are a valuable source of bioactive compounds with neuroprotective potential.

Oleanolic Acid Glycosides from Scabiosa caucasica and Scabiosa ochroleuca: Structural Analysis and Cytotoxicity

In the field of research on medicinal plants from the Armenian flora, the phytochemical study of two Scabiosa L. species, S. caucasica M. Bieb. and S. ochroleuca L. (Caprifoliaceae), has led to the isolation of five previously undescribed oleanolic acid glycosides from an aqueous-ethanolic extract of the roots: 3-O-α-L-rhamnopyranosyl-(1→3)-β-D-glucopyranosyl-(1→4)-β-D-glucopyranosyl-(1→4)-β-D-xylopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyloleanolic acid 28-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester, 3-O-β-D-xylopyranosyl-(1→2)-[α-L-rhamnopyranosyl-(1→4)]-β-D-glucopyranosyl-(1→4)-β-D-glucopyranosyl-(1→4)-β-D-xylopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyloleanolic acid 28-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester, 3-O-β-D-xylopyranosyl-(1→2)-[α-L-rhamnopyranosyl-(1→4)]-β-D-glucopyranosyl-(1→4)-β-D-glucopyranosyl-(1→4)-β-D-xylopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyloleanolic acid, 3-O-β-D-xylopyranosyl-(1→2)-[α-L-rhamnopyranosyl-(1→4)]-β-D-xylopyranosyl-(1→4)-β-D-glucopyranosyl-(1→4)-β-D-xylopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyloleanolic acid 28-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester, 3-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→4)-β-D-glucopyranosyl-(1→4)-β-D-xylopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyloleanolic acid 28-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester. Their full structural elucidation required extensive 1D and 2D NMR experiments, as well as mass spectrometry analysis. For the biological activity of the bidesmosidic saponins and the monodesmosidic saponin, their cytotoxicity on a mouse colon cancer cell line (MC-38) was evaluated.

Saponins of Selected Triterpenoids as Potential Therapeutic Agents: A Review

Saponins represent important natural derivatives of plant triterpenoids that are secondary plant metabolites. Saponins, also named glycoconjugates, are available both as natural and synthetic products. This review is focused on saponins of the oleanane, ursane, and lupane types of triterpenoids that include several plant triterpenoids displaying various important pharmacological effects. Additional convenient structural modifications of naturally-occurring plant products often result in enhancing the pharmacological effects of the parent natural structures. This is an important objective for all semisynthetic modifications of the reviewed plant products, and it is included in this review paper as well. The period covered by this review (2019–2022) is relatively short, mainly due to the existence of previously published review papers in recent years.

Two new triterpenoid saponins from the underground parts of Weigela x "Bristol Ruby"

Two new triterpenoid saponins, 3-O-β-D-xylopyranosyl-(1→4)-[β-D-xylopyranosyl-(1→3)]-β-D-glucopyranosyl-(1→4)-β-D-xylopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-β-D-arabinopyranosyloleanolic acid (1) and 3-O-β-D-xylopyranosyl-(1→4)-[α-L-arabinopyranosyl-(1→3)]-β-D-glucopyranosyl-(1→4)-β-D-xylopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-β-D-xylopyranosyloleanolic acid (2), were isolated and elucidated from the underground parts of Weigela x "Bristol Ruby". Their structures were established by interpretation of spectroscopic data (1 D and 2 D NMR) and mass spectrometry (MS).

Anti-phytopathogen terpenoid glycosides from the root bark of Chytranthus macrobotrys and Radlkofera calodendron

Chytranthus macrobotrys and Radlkofera calodendron are two Sapindaceae characterized by a lack of phytochemical data. Both root barks from the two Sapindaceae species were processed by ethanol extraction followed by the isolation of their primary constituents by liquid chromatography. This process yielded four previously undescribed terpenoid glycosides together with eight known analogues. Extracts and isolated compounds from C. macrobotrys and R. calodendron were then screened for antimicrobial activity against fifteen phytopathogens. The biological screening also involved extracts and pure compounds from Blighia unijugata and Blighia welwitschii, two Sapindaceae previously studied by our group. Phytopathogens were chosen based on their economic impact on agriculture worldwide. The selection was composed primarily of fungal species including; Pyricularia oryzae, Gaeumannomyces graminis var. tritici, Zymoseptoria tritici, Fusarium oxysporum, Botrytis cinerea, Pythium spp., Trichoderma spp. and Rhizoctonia solani. Furthermore, pure terpenoid glycosides were tested for the first time against wood-inhabiting phytopathogens such as; Phaeomoniella chlamydospora, Phaeoacremonium minimum, Fomitiporia mediterranea, Eutype lata and Xylella fastidiosa. Raw extracts exhibited different levels of activity dependent on the organism. Some pure compounds, including 3-O-α-L-arabinopyranosyl-(1 → 4)-β-D-xylopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin, 3-O-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin (α-hederin), 3-O-β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin (macranthoside A) and 3-O-α-L-arabinopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin (clemontanoside C), exhibited significant growth inhibitions on Pyricularia oryzae, Gaeumannomyces graminis var. tritici, Fomitiporia mediterranea and Zymoseptoria tritici. Monodesmoside triterpene saponins, in particular, exhibited MIC (IC₁₀₀) values as low as 25 μg/ml and IC₅₀ values as low as 10 μg/ml against these phytopathogens. Structure-activity relationships, as well as plant-microbe interactions, were discussed.

Semipapposides A-M, triterpenoid bidesmosides saponins from the roots of Scabiosa semipapposa

Phytochemical investigations of the roots of Scabiosa semipapposa Salzem ex D.C. have led to the isolation of 12 undescribed triterpenoid saponins named semipapposides A-L, one undescribed saponin semipapposide M obtained as an inseparable mixture, together with three known oleanolic acid glycosides. Their structures were elucidated by analysis of 1D and 2D-NMR (¹H-¹H COSY, TOCSY, HSQC-TOCSY, HSQC, ROESY or NOESY, and HMBC) spectroscopic data and mass spectrometry (HR-ESI-MS), and by comparison with those of related metabolites. All saponins possess a partial sequence rhamnopyranosyl-(1 → 2)-xylopyranosyl or rhamnopyranosyl-(1 → 2)-arabinopyranosyl- at C-3 of the aglycon and a gentiobiose unit at C-28. These results represent a contribution to the knowledge of the saponins of Scabiosa species and their chemotaxonomy.

Triterpene glycosides from Blighia welwitschii and evaluation of their antibody recognition capacity in multiple sclerosis

Multiple sclerosis (MS) in a multifactorial autoimmune disease in which reliable biomarkers are needed for therapeutic monitoring and diagnosis. Autoantibodies (autoAbs) are known biomarker candidates although their detection in biological fluids requires a thorough characterization of their associated antigens. Over the past twenty years, a reverse chemical-based approach aiming to screen putative autoantigens has underlined the role of glycans, in particular glucose, in MS. Despite the progress achieved, a lack of consensus regarding the nature of innate antigens as well as difficulties proposing new synthetic glucose-based structures have proved to be obstacles. Here is proposed a strategy to extend the current methodology to the field of natural glycosides, in order to dramatically increase the diversity of glycans that could be tested. Triterpene saponins from the Sapindaceace family represent an optimal starting material as their abundant description in the literature has revealed a prevalence of glucose-based oligosaccharides. Blighia welwitschii (Sapindaceae) was thus selected as a case study and twelve triterpene saponins were isolated and characterized. Their structures were elucidated on the basis of 1D and 2D NMR as well as mass spectrometry, revealing seven undescribed compounds. A selection of natural glycosides exhibiting various oligosaccharide moieties were then tested as antigens in enzyme-linked immunosorbent assay (ELISA) to recognize IgM antibodies (Abs) in MS patients' sera. Immunoassay results indicated a correlation between the glycan structures and their antibody recognition capacity, allowing the determination of structure-activity relationships that were coherent with previous studies. This approach might help to identify sugar epitopes putatively involved in MS pathogenesis, which remains poorly understood.

New triterpenoid saponin glycosides from the fruit fibers ofTrichosanthes cucumerinaL

Five new triterpenoid saponin glycosides, trichocucumerisides A–E (1–5), together with eleven known compounds (6–16) were isolated from Trichosanthes cucumerina fruit fibers. The structures of the new compounds were elucidated by detailed analysis of NMR and mass spectroscopic data as well as chemical reactions. The anti-inflammatory study against nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated RAW264.7 cells shows that compounds 7 and 9 exhibited stronger NO inhibitory activity, with IC₅₀ values of 3.0 and 2.7 μM, respectively, with comparison to positive references Celecoxib and aminoguanidine (IC₅₀ values 75.7 and 75.0 μM, respectively). Compounds 7 and 9 also possessed a greater selectivity index (SI) of approximately 3–4-fold activity than that of the positive references.

The new glycosides 1–5, together with eleven known compounds were isolated. Two compounds exhibited more potent anti-inflammatory activity than Celecoxib and aminoguanidine reference compounds.

Hederagenin glycosides from the fruits of Blighia unijugata

A phytochemical investigation of Blighia unijugata led to the isolation of eleven hederagenin glycosides. Among these compounds, six are previously undescribed, two are described in their native forms for the first time and three are known whereas firstly isolated from Blighia unijugata. The structure of the undescribed compounds was elucidated on the basis of 2D NMR and mass spectrometry analyses as 3-O-β-D-xylopyranosyl-(1 → 3)-α-L-arabinopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin, 3-O-β-D-xylopyranosyl-(1 → 3)-α-L-arabinopyranosyl-(1 → 4)-3-O-acetyl-β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin, 3-O-β-D-glucopyranosyl-(1 → 3)-α-L-arabinopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin, 3-O-β-D-xylopyranosyl-(1 → 3)-β-D-xylopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin, 3-O-β-D-xylopyranosyl-(1 → 3)-β-D-xylopyranosyl-(1 → 4)-3-O-acetyl-β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin, 3-O-α-L-arabinopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin 28-O-β-D-glucopyranosyl-(1 → 6)-β-D-glucopyranosyl ester, 3-O-α-L-arabinopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin 28-O-β-D-glucopyranosyl ester and 3-O-β-D-xylopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin 28-O-β-D-glucopyranosyl ester. These results revealed the existence of several conserved structural features that could be used as chemotaxonomic markers for the Blighia genus such as the glycosidic sequence 3-O-α-L-arabinopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyl, the occurrence of 3-O-acetylated β-D-glucopyranosyl units and the systematic presence of hederagenin as aglycone.

Phytochemistry of Weigela x “kosteriana variegata” (Caprifoliaceae)

One new triterpene glycoside 3- O-β-D-xylopyranosyl-(1→4)-[β-D-glucopyranosyl-(1→3)]-β-D-xylopyranosyl-(1→4)-β-D-xylopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyloleanolic acid, was isolated from Weigela x “kosteriana variegata” (Caprifoliaceae), with three known ones. Their structures were characterized by a combination of mass spectrometry and 1D and 2D NMR spectrocopic techniques including 1H- and 13C NMR, COSY, TOCSY, NOESY, HSQC, and HMBC experiments. The toxicological properties of some glycosides were determined with a zebrafish-based assay. The results show that the most active compounds were toxic to the larvae in the range of 1 μM.

Phytotoxic triterpene saponins from Bellis longifolia, an endemic plant of Crete

In a study of 62 plant species of the Cretan flora for their phytotoxic activity, plants were extracted successively with CH₂Cl₂, MeOH and H₂O. Phytotoxicity evaluation of the 240 extracts was performed against Lactuca sativa L. and Agrostis stolonifera L.. The MeOH extract of Bellis longifolia was the most phytotoxic. Bioassay-guided fractionation revealed that a fraction consisting mainly of saponins was the most effective. Separation of the saponins was performed using initially a step-gradient Centrifugal Partition Chromatography (CPC). Investigation of the active fraction led to the isolation and structure elucidation of three previously undescribed triterpene saponins, 3-O-β-D-fucopyranosyl polygalacic acid, 28-O-α-L-rhamnopyranosyl-(1 → 2)-β-D-fucopyranosyl polygalacic acid and 3-O-β-D-fucopyranosyl-2α,3β,23-trihydroxyolean-12-en-28-oic acid, which were present as the main phytotoxic compounds of the methanol extract. Two triterpenes, polygalacic acid and bellisonic acid and four kaempferol glucosides, as well as chlorogenic acid were also isolated. 3-O-β-D-fucopyranosyl polygalacic acid and 3-O-β-D-fucopyranosyl-2α,3β,23-trihydroxyolean-12-en-28-oic acid had phytotoxic activity similar to some commercial herbicides (IC₅₀ values of ca. 25 μM) against duckweed (Lemna paucicostata).

Oleanane-type glycosides from Pittosporum tenuifolium "variegatum" and P. tenuifolium "gold star"

The phytochemical study of two cultivars of Pittosporum tenuifolium Banks & Sol. ex Gaertn, "variegatum" and "gold star", led to the isolation of eight oleanane-type glycosides: seven previously undescribed and a known one. Their aglycons are oxygenated oleanane derivatives as barringtogenol C, camelliagenin A, hederagenin, and 22α-hydroxyoleanolic acid. Their structures were established by 2D NMR spectroscopic techniques and mass spectrometry as 3-O-β-D-galactopyranosyl-(1 → 2)-[α-L-arabinopyranosyl-(1 → 3)]-β-D-glucuronopyranosyl-21-O-angeloyl-22-O-acetylbarringtogenol C, 3-O-β-D-galactopyranosyl-(1 → 2)-[α-L-arabinopyranosyl-(1 → 3)]-β-D-glucuronopyranosyl-21,22-di-O-angeloylbarringtogenol C, 3-O-β-D-galactopyranosyl-(1 → 2)-[α-L-arabinopyranosyl-(1 → 3)]-β-D-glucuronopyranosyl-22-O-angeloylcamelliagenin A, 3-O-β-D-glucopyranosyl-(1 → 2)-[β-D-glucopyranosyl-(1 → 6)]-β-D-glucopyranosyl-22-O-[(6-O-acetyl)-β-D-glucopyranosyl]camelliagenin A, 3-O-β-D-galactopyranosyl-(1 → 2)-[α-L-arabinofuranosyl-(1 → 4)]-β-D-glucuronopyranosylhederagenin 28-O-β-D-glucopyranosyl ester, 3-O-α-L-arabinofuranosyl-(1 → 4)-β-D-glucuronopyranosylhederagenin 28-O-β-D-glucopyranosyl ester, 3-O-β-D-galactopyranosyl-(1 → 2)-[α-L-arabinofuranosyl-(1 → 4)]-β-D-glucuronopyranosyl-22α-hydroxyoleanolic acid 28-O-β-D-glucopyranosyl ester, and the known ilexoside XLIX. These results represent a significative contribution to the chemotaxonomy of the genus Pittosporum, highlighting hederagenin-type saponins as chemotaxonomic markers of P. tenuifolium cultivars.