Quassinoids: Phytochemistry and antitumor prospect.

Quassinoids, originating from the oxidative degradation of tetracyclic tirucallane triterpene, are a diverse class of secondary metabolites identifying from nature mostly in Simaroubaceae family. The crucial pharmacological activities and structural complexity of quassinoids have long fascinated scientists due to their medicinal uses, infamous toxicity, and unique biosynthesis. In the past few decades, 482 quassinoids, assigned to 6 skeletons, have been isolated and identified from plants. The names, classes, molecular formula, and plant sources of these secondary metabolites are collated here. This review will be a detailed update of the naturally occurring quassinoids reported from the plant kingdom, providing an in-depth discussion of their diversity, antitumor activities, structure-activity relationship.

A new dilignan from the twigs and leaves of Archidendron clypearia.

Previous work has shown that the lignans from the twigs and leaves of Archidendron clypearia (Jack) I.C.N. possess anti-ß-amyloid aggregation activity. Here we report a new dilignan, archidendronin A (1), along with one known sesquilignan (2). Their structures were determined by extensive spectroscopic methods, including UV, HRESIMS, 1 D and 2 D NMR data. The inhibitory activity on Aß1-42 aggregation was screened by ThT assay with curcumin as the positive control, and compounds 1 and 2 showed inhibition rate of 60.0% and 64.4% at 20 µM, respectively.[Formula: see text].

Lignans and neolignans with isovaleroyloxy moiety from Solanum lyratum Thunb.: Chiral resolution, configurational assignment and neuroprotective effects.

Eight pairs of enantiomeric lignans and neolignans including thirteen undescribed compounds, along with an undescribed meso compound, were isolated from the herbs of Solanum lyratum Thunb.(Solanaceae). Their structures and relative configurations were determined by extensive spectroscopic analyses of HRESIMS and nuclear magnetic resonance. The absolute configurations of the pure isomers were established based on the cooperative comparison between the experimental and calculated electronic circular dichroism (ECD) and optical rotation (OR). It is interesting that we obtained several naturally occurring stereoisomers with the identical gross structure possessing several stereogenic carbons from S. lyratum. Additionally, all isolates were assessed for neuroprotective effects toward human neuroblastoma SH-SY5Y cells injury induced by H2O2.

Terpenylated coumarins from the root bark of Ailanthus altissima (Mill.) Swingle.

Seven undescribed terpenylated coumarins, named altissimacoumarin I-O, together with seven known compounds, altissimacoumarin C, altissimacoumarin E, altissimacoumarin G, altissimacoumarin H, puberulin, 7-(3-Methyl-2-butenyloxy)-6-methoxycoumarin and artelin were isolated from the root bark of Ailanthus altissima (Mill.) Swingle. Their structures were elucidated by comprehensive spectra data analysis, NMR calculation, DP4+ analysis and ACD/Structure Elucidator software simulation. The absolute configurations of altissimacoumarins K, L, M and N were determined by modified Mosher's method. All isolates were tested for their cytotoxic effect against two hepatoma carcinoma cell lines (HepG2, Hep3B). Altissimacoumarin C exhibited moderate cytotoxic effect against Hep3B cells, with IC50 of 45.21 µM.

Functional Characterization and Structural Basis of an Efficient Di-C-glycosyltransferase from Glycyrrhiza glabra.

A highly efficient di-C-glycosyltransferase GgCGT was discovered from the medicinal plant Glycyrrhiza glabra. GgCGT catalyzes a two-step di-C-glycosylation of flopropione-containing substrates with conversion rates of >98%. To elucidate the catalytic mechanisms of GgCGT, we solved its crystal structures in complex with UDP-Glc, UDP-Gal, UDP/phloretin, and UDP/nothofagin, respectively. Structural analysis revealed that the sugar donor selectivity was controlled by the hydrogen-bond interactions of sugar hydroxyl groups with D390 and other key residues. The di-C-glycosylation capability of GgCGT was attributed to a spacious substrate-binding tunnel, and the G389K mutation could switch di- to mono-C-glycosylation. GgCGT is the first di-C-glycosyltransferase with a crystal structure, and the first C-glycosyltransferase with a complex structure containing a sugar acceptor. This work could benefit the development of efficient biocatalysts to synthesize C-glycosides with medicinal potential.

Isolation of macrocarpene-type sesquiterpenes from stigma maydis with neuroprotective activities.

Five undescribed macrocarpene-type sesquiterpenes (1-5), along with a known analogue (6) were isolated from the crude extract of stigma maydis. The structures of these compounds were elucidated based on comprehensive spectroscopic analyses together with quantum chemical calculations of 13C NMR data and electronic circular dichroism (ECD) curves. All isolated compounds were tested for their neuroprotective effects against the injury of human neuroblastoma SH-SY5Y cells induced by H2O2. Among them, compounds 3 (65.89%) and 5 (64.38%) showed moderate neuroprotective activity at 50 µM.

Network pharmacology-based screening of the active ingredients and potential targets of the genus of Pithecellobium marthae (Britton & Killip) Niezgoda & Nevl for application to Alzheimer's disease.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder associated with synaptic dysfunction, pathological accumulation of ß-amyloid (Aß), and neuronal loss. Given the prevalence of AD and the lack of effective long-term therapies, there is a pressing need to discover viable leads that can be developed into clinically approved drugs with disease-modifying effects. The analysis of current reported literatures confirms the importance of the plants of Pithecellobium genus as candidate against AD. Hence, it is necessary to identify selective anti-dementia agents from this genus. To explore potential compounds with marked effect on AD in Pithecellobium genus, a compound database based on the methods of network pharmacology prediction was established in this paper by constructing the compound-disease target network. The result showed that the most effective compound in the plants of this genus might be (7'R,8'R)-7'-methoxyl strebluslignanol, and the most potential target might be Macrophage colony-stimulating factor 1 receptor.

Prenylated flavans from Daphne giraldii and their cytotoxic activities.

Nine new prenylated flavan compounds with multi-chiral centers including two pairs of epimers were isolated from the stem and root bark of Daphne giraldii. Their structures were established by extensive NMR and HR-ESIMS spectroscopic data analyses. The in vitro cytotoxicity experiments indicated that compound 6 showed the most significant cytotoxicity against Hep3B cells, with an IC50 value of 9.83 µM. Hoechst 33258 and Annexin V-FITC/PI staining suggested that 6 could induce apoptosis of Hep3B cells in a concentration-dependent manner. Further mechanism study indicated that the apoptosis was associated with the up-regulations of Bax, cl-PARP and a decrease in Bcl-2 expression.

Cytotoxic clerodane diterpenoids from Croton crassifolius.

Hepatocellular carcinoma (HCC) is the most common type of liver cancer, and treatment options for HCC are limited. In addition, the discovery of new natural compounds with anti-hepatocarcinoma activity is attracting increasing attention. For this reason, phytochemical investigation of Croton crassifolius led to the isolation of 17 diterpenoids, including three new clerodane diterpenoids, named crassifolius A-C (1-3), along with 14 known ones (4-17). Their structures were established by 1D, 2D NMR, HR-ESI-MS, detailed calculated electronic circular dichroism (ECD) spectra and the assistance of quantum chemical predictions (QCP) of 13C NMR chemical shifts. The cytotoxicities of all these compounds against human liver cancer lines (HepG2 and Hep3B) were determined. Among them, compound 1 exhibited good cytotoxicity with IC50 value of 17.91µM against human liver tumor cells Hep3B. Following further studies of the anti-tumor mechanism of compound 1-induced cell growth inhibition, we found that compound 1 caused apoptotic cell death in Hep3B cells by detecting morphologic changes and Western blotting analysis.

Therapeutic effect of Qingyi decoction in severe acute pancreatitis-induced intestinal barrier injury.

AIM: To investigate the effect of Qingyi decoction on the expression of secreted phospholipase A2 (sPLA2) in intestinal barrier injury. METHODS: Fifty healthy Sprague-Dawley rats were randomly divided into control, severe acute pancreatitis (SAP), Qingyi decoction-treated (QYT), dexamethasone-treated (DEX), and verapamil-treated (VER) groups. The SAP model was induced by retrograde infusion of 1.5% sodium deoxycholate into the biliopancreatic duct of the rats. All rats were sacrificed 24 h post-SAP induction. Arterial blood, intestine, and pancreas from each rat were harvested for investigations. The levels of serum amylase (AMY) and diamine oxidase (DAO) were determined using biochemical methods, and serum tumor necrosis factor (TNF)-α level was measured by an enzyme linked immunosorbent assay. Pathologic changes in the harvested tissues were investigated by microscopic examination of hematoxylin and eosin-stained tissue sections. The expressions of sPLA2 at mRNA and protein levels were detected by reverse transcriptase PCR and Western blot, respectively. A terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay was used to investigate apoptosis of epithelial cells in the intestinal tissues. RESULTS: Compared to the control group, the expression of sPLA2 at both the mRNA and protein levels increased significantly in the SAP group (0.36 ± 0.13 vs 0.90 ± 0.38, and 0.16 ± 0.05 vs 0.64 ± 0.05, respectively; Ps < 0.01). The levels of AMY, TNF-α and DAO in serum were also significantly increased (917 ± 62 U/L vs 6870 ± 810 U/L, 59.7 ± 14.3 ng/L vs 180.5 ± 20.1 ng/L, and 10.37 ± 2.44 U/L vs 37.89 ± 5.86 U/L, respectively; Ps < 0.01). The apoptosis index of intestinal epithelial cells also differed significantly between the SAP and control rats (0.05 ± 0.02 vs 0.26 ± 0.06; P < 0.01). The serum levels of DAO and TNF-α, and the intestinal apoptosis index significantly correlated with sPLA2 expression in the intestine (r = 0.895, 0.893 and 0.926, respectively; Ps < 0.05). The levels of sPLA2, AMY, TNF-α, and DAO in the QYT, VER, and DEX groups were all decreased compared with the SAP group, but not the control group. Qingyi decoction intervention, however, gave the most therapeutic effect against intestinal barrier damage, although the onset of its therapeutic effect was slower. CONCLUSION: Qingyi decoction ameliorates acute pancreatitis-induced intestinal barrier injury by inhibiting the overexpression of intestinal sPLA2. This mechanism may be similar to that of verapamil.