Three new homoisoflavanone glycosides from the bulbs of Ornithogalum caudatum

Isolation and characterization of dihydrohomoisoflavonoids from Portulaca oleracea L

Eight pairs of dihydrohomoisoflavonoids (1-8), including four pairs of enantiomeric aglycones [(R,S)-portulacanones B (1) and C (2) and (R,S)-oleracones C (3) and Q (4)] and four pairs of epimeric glycosides [portulacasides A-D and epiportulacasides A-D (5-8)], were obtained from Portulaca oleracea L. Among them, (R,S)-oleracone Q (4) and four pairs of epimeric glycosides (5-8) were reported for the first time. The 50% EtOH fraction from the 70% EtOH extract prevented HepG2 human liver cancer cell damage induced by N-acetyl-p-aminophenol (APAP), and the cell survival rate was 62.3%. Portulacaside B (6a), which was isolated from the 50% EtOH fraction, exhibited hepatoprotective and anti-inflammatory effects. The compound increased the survival rate of APAP-damaged HepG2 human liver cancer cells from 40.0% to 51.2% and reduced nitric oxide production in RAW 264.7 macrophages, resulting in an inhibitory rate of 46.8%.

Antiviral Activities of Compounds Isolated from Pinus densiflora (Pine Tree) against the Influenza A Virus

Pinus densiflora was screened in an ongoing project to discover anti-influenza candidates from natural products. An extensive phytochemical investigation provided 26 compounds, including two new megastigmane glycosides (1 and 2), 21 diterpenoids (3–23), and three flavonoids (24–26). The chemical structures were elucidated by a series of chemical reactions, including modified Mosher’s analysis and various spectroscopic measurements such as LC/MS and 1D- and 2D-NMR. The anti-influenza A activities of all isolates were screened by cytopathic effect (CPE) inhibition assays and neuraminidase (NA) inhibition assays. Ten candidates were selected, and detailed mechanistic studies were performed by various assays, such as Western blot, immunofluorescence, real-time PCR and flow cytometry. Compound 5 exerted its antiviral activity not by direct neutralizing virion surface proteins, such as HA, but by inhibiting the expression of viral mRNA. In contrast, compound 24 showed NA inhibitory activity in a noncompetitive manner with little effect on viral mRNA expression. Interestingly, both compounds 5 and 24 were shown to inhibit nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) expression in a dose-dependent manner. Taken together, these results provide not only the chemical profiling of P. densiflora but also anti-influenza A candidates.

Naturally Occurring Homoisoflavonoids: Phytochemistry, Biological Activities and Synthesis

This review covers the phytochemical, biological properties, and synthesis of naturally occurring homoisoflavonoids. Homoisoflavonoids are a very important class of secondary metabolites whose numbers have grown from 20 in 1981 to 157 at the present time. They are found to occur in seven plant families. For the purpose of this review they are classified into five groups: 3-benzylchroman-4-ones, 3-benzylflavans, Δ3,9 and Δ2,3 3-benzylchroman-4-ones, benzocyclobutenes (scillascillins) and rearranged homoisoflavonoids (brazilin and related compounds). Biosynthetically, the 3-benzylchroman-4-ones and the 3-hydroxy-derivatives have been shown to arise from a chalcone precursor (sappanchalcone) and there is strong evidence that this isolable intermediate can be converted into the diverse structures such as the benzocyclobutenes (scillascillins) and the rearranged, brazilin-type compounds. Homoisoflavonoids possess a wide range of biological activities, including, antimicrobial, antimutagenic, anti-inflammatory, antidiabetic, etc, properties. The review also surveys the chemical synthesis of natural homoisoflavonoids. Analytical methods for the determination of these important metabolites are also reviewed. The last section is devoted to a brief review of the diagnostic NMR spectroscopic features of homoisoflavonoids. A comprehensive Table has also been compiled listing all known metabolites, their sources, melting points and optical rotation values (where available) and references.

Isolation and characterization of a multifunctional flavonoid glycosyltransferase from Ornithogalum caudatum with glycosidase activity

Glycosyltransferases (GTs) are bidirectional biocatalysts catalyzing the glycosylation of diverse molecules. However, the extensive applications of GTs in glycosides formation are limited due to their requirements of expensive nucleotide diphosphate (NDP)-sugars or NDP as the substrates. Here, in an effort to characterize flexible GTs for glycodiversification of natural products, we isolated a cDNA, designated as OcUGT1 from Ornithogalum caudatum, which encoded a flavonoid GT that was able to catalyze the trans-glycosylation reactions, allowing the formation of glycosides without the additions of NDP-sugars or NDP. In addition, OcUGT1 was observed to exhibit additional five types of functions, including classical sugar transfer reaction and three reversible reactions namely NDP-sugar synthesis, sugars exchange and aglycons exchange reactions, as well as enzymatic hydrolysis reaction, suggesting OcUGT1 displays both glycosyltransferase and glycosidase activities. Expression profiles revealed that the expression of OcUGT1 was development-dependent and affected by environmental factors. The unusual multifunctionality of OcUGT1 broadens the applicability of OcUGT1, thereby generating diverse carbohydrate-containing structures.

Transcriptome-guided discovery and functional characterization of two UDP-sugar 4-epimerase families involved in the biosynthesis of anti-tumor polysaccharides in Ornithogalum caudatum

A transcriptome-guided discovery and functional identification of UGE and UXE families were presented. Importantly, OcUGE1/2 and OcUXE1 were preliminarily revealed to be responsible for the biosynthesis of anticancer polysaccharides inO. caudatum.

Transcriptome-wide identification of sucrose synthase genes in Ornithogalum caudatum

A transcriptome-wide discovery and functional identification of a sucrose synthase family was presented. Importantly, OcSus1 and OcSus2 were first verified to be responsible for the biosynthesis of glucose-containing polysaccharides inO. caudatum.

The chemistry and biological activity of the Hyacinthaceae

The Hyacinthaceae (sensu APGII), with approximately 900 species in about 70 genera, can be divided into three main subfamilies, the Hyacinthoideae, the Urgineoideae and the Ornithogaloideae, with a small fourth subfamily the Oziroëoideae, restricted to South America. The plants included in this family have long been used in traditional medicine for a wide range of medicinal applications. This, together with some significant toxicity to livestock has led to the chemical composition of many of the species being investigated. The compounds found are, for the most part, subfamily-restricted, with homoisoflavanones and spirocyclic nortriterpenoids characterising the Hyacinthoideae, bufadienolides characterising the Urgineoideae, and cardenolides and steroidal glycosides characterising the Ornithogaloideae. The phytochemical profiles of 38 genera of the Hyacinthaceae will be discussed as well as any biological activity associated with both crude extracts and compounds isolated. The Hyacinthaceae of southern Africa were last reviewed in 2000 (T. S. Pohl, N. R. Crouch and D. A. Mulholland, Curr. Org. Chem., 2000, 4, 1287-1324; ref. 1); the current contribution considers the family at a global level.

Chemical constituents from the rhizomes of Smilax glabra and their antimicrobial activity

Six new phenolic compounds, named smiglabrone A (1), smiglabrone B (2), smilachromanone (3), smiglastilbene (4), smiglactone (5), smiglabrol (6), together with fifty-seven known ones 7–63were isolated from the rhizomes of Smilax glabra. Their structures were elucidated on the basis of extensive spectroscopic analyses, as well as by comparison with literature data. Twenty-seven of these compounds were obtained from and identified in the genus Smilax for the first time. The absolute configuration of (2S)-1,2-O-di-trans-p-coumaroylglycerol (43) was determined for the first time using the exciton-coupled circular dichroism (ECCD) method. Thirty isolated compounds were evaluated for their antimicrobial activity against three Gram-negative bacteria, three Gram-positive bacteria and one fungus, and the corresponding structure-activity relationships were also discussed. Eighteen compounds were found to be antimicrobial against the microorganisms tested and the minimum inhibitory concentrations (MIC) were in the range of 0.0794–3.09 mM. Among them, compound 1 showed antimicrobial activity against Canidia albicans with MIC value of 0.146 mM, which was stronger than cinchonain Ia with an MIC of 0.332 mM. Compounds 3 and 4 exhibited inhibitory activity against Staphylococcus aureus with MIC values of 0.303 and 0.205 mM, respectively. The results indicated that these antimicrobial constituents of this crude drug might be responsible for its clinical antimicrobial effect.

Homoisoflavonoids from the fibrous roots of Polygonatum odoratum with glucose uptake-stimulatory activity in 3T3-L1 adipocytes

The EtOAc-soluble fraction of a 90% MeOH extract of the fibrous roots of Polygonatum odoratum was found to potentiate insulin-stimulated glucose uptake in differentiated 3T3-L1 adipocytes. Bioassay-guided fractionation yielded nine homoisoflavonoids (1-9), four of which were new (1-4), together with an isoflavone glycoside (10) and a flavanone glycoside (11). The structures of new compounds were elucidated on the basis of extensive 1D and 2D NMR spectroscopy, and the absolute configurations were deduced by CD spectra. All 11 compounds showed effects of sensitizing adipocytes for insulin in a cell-based glucose uptake assay using 3T3-L1 adipocytes. The results indicate that homoisoflavonoids may be potential insulin sensitizers.