New Indole Glycosides from Aesculus chinensis var. chekiangensis and Their Neuroprotective Activities

N-Si Heterolysis by Chiral (BOX)Cu(OTf)2 Catalysts for the Synthesis of Indole and Carbazole Glycosides

Chiral Cu(II) bisoxazolines have been shown to catalyze the coupling of acetyl-protected carbohydrates with N-silylated indoles to give the corresponding N-glycosides. Preliminary mechanistic experiments indicated that catalysis occurs through formation of a Cu-indolide complex with concomitant formation of TMS-OTf which together activate the sugar and deliver the indole nucleophile.

Antihyperglycemic effects of triterpenoid saponins from the seeds of Aesculus chinensis Bge

Six undescribed triterpenoid saponins, namely aescuchinosides A-F, along with seven known triterpenoid saponins, were isolated from the seeds of Aesculus chinensis. Barrigenol-like triterpenoids (BATs) constitute these saponins. Protoaescigenin serves as their aglycone, with various oxygen-containing groups, including acetyl, isobutyryl, tigloyl, and angeloyl groups situated at C-21, C-22, and C-28. Various techniques, including 1D and 2D-NMR spectroscopy, high-resolution mass spectrometry, and acid hydrolysis, were employed to determine the structures of these compounds. The antihyperglycemic effects of the isolated compounds were examined in insulin -resistant HepG2 cells induced by palmitic acid treatment. At a concentration of 6 μM, aesculinoside F exhibited a significant increase in glucose consumption. In addition, aesculinoside F demonstrated the potential to improve insulin resistant by upregulating the PI3K/AKT pathway. These results indicate that the seeds of A.chinensis hold promising potential for preventing insulin resistant related disease.

Exploiting π and Chalcogen Interactions for the β-Selective Glycosylation of Indoles through Glycal Conformational Distortion

Harnessing unconventional noncovalent interactions (NCIs) is emerging as a formidable synthetic approach in difficult-to-access glycosidic chemical space. C-Glycosylation, in particular, has gained a flurry of recent attention. However, most reported methods are restricted to the relatively facile access to α-C-glycosides. Herein, we disclose a β-stereoselective glycosylation of indoles by employing a phosphonoselenide catalyst. The robustness of this protocol is exemplified by its amenability for reaction at both the indolyl C- and N- reactivity sites. In contrast to previous reports, in which the chalcogens were solely involved in Lewis acidic activation, our mechanistic investigation unraveled that the often neglected flanking aromatic substituents of phosphonoselenides can substantially contribute to catalysis by engaging in π-interactions. Computations and NMR spectroscopy indicated that the chalcogenic and aromatic components of the catalyst can be collectively exploited to foster conformational distortion of the glycal away from the usual half-chair to the boat conformation, which liberates the convex β-face for nucleophilic attack.

Nitrogenous compounds from Aesculus wilsonii seeds

Eight nitrogenous compounds including five undescribed ones, aeswilnitrousol A (1), aeswilnitrousosides BD (2-4), and 6-(2-hydroxy-3-methylbutylamino)-8-oxoadenine (5) were isolated from the seeds of Aesculus wilsonii. Their structures and absolute configurations were established based on spectroscopic determination, calculated electronic circular dichroism (ECD) analysis, as well as chemical reaction methods. Among the three known compounds, 7 and 8 were obtained from the Aesculus genus for the first time, and 6 was gained from this plant initially. The 13C NMR data of 7 and 8 were reported for the first time. Moreover, the inhibitory effect of all the isolates against LPS-induced nitric oxide production in RAW264.7 macrophages was evaluated. As a result, compounds 2 and 8 exhibited anti-inflammatory activity in a concentration-dependent manner at 10, 25, and 50 μM.

Panaxindole, a novel indole alkaloid N-glucoside from the leaves of Panax vietnamensis Ha et Grushv. (Vietnamese ginseng)

Vietnamese ginseng (Panax vietnamensis Ha and Grushv., Araliaceae) is indigenous in the central highlands of Vietnam and the southernmost distribution in the Panax genus. Like other ginseng, Vietnamese ginseng is well known has been used as a tonic and for management of certain diseases in the traditional medicine. Nevertheless, it is noteworthy that in respect to the long history in use and systematic studied on Korean ginseng (P. ginseng), American ginseng (P. quinquefolius), Japanese ginseng (P. japonicus), and Chinese ginseng (P. notoginseng), the up-to-date published database on Vietnamese ginseng is relatively much less extensive. In our ongoing research on the promising Vietnamese medicinal plants, the present phytochemical investigation of the ethanol extract of the leaves of Panax vietnamensis led to the isolation of three compounds (1-3), including a new indole alkaloid N-glycoside (1) and two known compounds. Their structures were elucidated based on extensive physiochemical and chemical methods, especially the interpretation of NMR and MS spectra. The absolute configuration of 1 was determined based on the comparison of its experimental and theoretical ECD spectra along with NMR calculation. Compound 1 is naturally isolated N-glycoside, which is rarely found in natural products. The isolated compounds showed weak or no inhibitory activity against acetylcholinesterase enzyme (AChE).

The current scenario of naturally occurring indole alkaloids with anticancer potential

Naturally occurring indole alkaloids are ubiquitously present in nature and possess extensive biological properties and structural diversity. Mechanistically, naturally occurring indole alkaloids have the potential to inhibit cancer cell proliferation, arrest cell cycle and induce apoptosis. Accordingly, naturally occurring indole alkaloids exhibit promising activity against both drug-sensitive and drug-resistant cancers including multidrug-resistant forms. Therefore, naturally occurring indole alkaloids constitute an important source of anticancer drug leads and candidates. The goal of this review is to highlight the current scenario of naturally occurring indole alkaloids with anticancer potential, covering articles published from 2018 to present. The names, sources, and antiproliferative activity are discussed to continuously open up a map for the remarkable exploration of more effective candidates.

NO Release Inhibitory Activity of Flavonoids from Aesculus Wilsonii Seeds through MAPK (P38), NF-κB, and STAT3 Cross-Talk Signaling Pathways

The flavonoid constituents of Aesculus wilsonii, a source of the Chinese medicinal drug Suo Luo Zi, and their in vitro anti-inflammatory effects were investigated. Fifteen flavonoids, including aeswilflavonosides IA-IC (1:  - 3: ) and aeswilflavonosides IIA-IIE (4:  - 8: ), along with seven known derivatives were isolated from a seed extract. Their structures were elucidated by extensive spectroscopic methods, acid and alkaline hydrolysis, and calculated electronic circular dichroism spectra. Among them, compounds 3: and 7: possess a 5-[2-(carboxymethyl)-5-oxocyclopent-yl]pent-3-enylate or oleuropeoylate substituent, respectively, which are rarely reported in flavonoids. Compounds 2, 3, 7: , and 12:  - 15: were found to inhibit lipopolysaccharide-induced nitric oxide production in RAW 264.7 cell lines. In a mechanistic assay, the flavonoid glycosides 2, 3: , and 7: reduced the expressions of interleukin-6 and tumor necrosis factor-alpha induced by lipopolysaccharide. Further investigations suggest that 2: and 3: downregulated the protein expression of tumor necrosis factor-alpha and interleukin-6 by inhibiting the phosphorylation of p38. Compound 7: was found to reduce the production of inducible nitric oxide synthase, and the secretion of tumor necrosis factor-alpha and interleukin-6 through inhibiting nuclear factor kappa-light-chain-enhancer of activated B signaling pathway. Compounds 2, 3: , and 7: possessed moderate inhibitory activity on the expression of signal transducer and activator of transcription-3. Taken together, the data indicate that the flavonoid glycosides of A. wilsonii seeds exhibit nitric oxide release inhibitory activity through mitogen-activated protein kinase (p38), nuclear factor kappa-light-chain-enhancer of activated B, and signal transducer and activator of transcription-3 cross-talk signaling pathways.

Comparative Metabolomics of Reproductive Organs in the Genus Aesculus (Sapindaceae) Reveals That Immature Fruits Are a Key Organ of Procyanidin Accumulation and Bioactivity

Fruit from A. hippocastanum L. are used commercially for chronic venous insufficiency (CVI). The isomeric mixture of pentacyclic triterpenoid saponins (β-aescin) exert anti-inflammatory effects. Hence, research has focused on β-aescin, yet the diversity, accumulation, and bioactivity of organ-specific secondary metabolites represent missed pharmacological opportunities. To this end, we applied an untargeted metabolomics approach by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to the chemical profiles of flowers, immature fruits, and pedicels from 40 specimens across 18 species of Aesculus. Principal component analysis (PCA), orthogonal partial least squares (OPLS-DA), and molecular networking revealed stronger chemical differences between plant organs, than between species. Flowers are rich in glycosylated flavonoids, pedicels in organic acids and flavonoid aglycones, and immature fruits in monomeric flavan-3-ols and procyanidins. Although a high diversity of flavonoids and procyanidins was observed, the relative amounts differed by plant organ. Fruit extracts demonstrated the strongest antifungal (Saccharomyces cerevisiae) and antioxidant activity, likely from the procyanidins. Overall, secondary metabolite profiles are organ-specific, and fruits accumulate antifungal and antioxidant compounds. Due to the chemical similarity between species, similar effects may be achieved between species. This creates incentives for further exploration of the entire genus, in bioprospecting for potential therapeutic leads.

Phenylethanol glycosides from the seeds of Aesculus chinensis var. chekiangensis

Three new phenylethanol glycosides (1-3) and one known analogue (4) were isolated from the seeds of Aesculus chinensis Bge. var. chekiangensis. To the best of our knowledge, this represents the first isolation of phenylethanol glycosides from the genus of Aesculus, which enriched its chemical composition. Structure elucidations were performed via extensive NMR and HRESIMS data together with comparison with literature data. Thereafter, the isolated compounds were assayed for their neuroprotective activities against CoCl₂-induced cytotoxicity in PC12 cells and compound 3 exhibited moderate activity.