Isolation and structure elucidation of new PKCalpha inhibitors from Pinus flexilis

Plantainoside D Reduces Depolarization-Evoked Glutamate Release from Rat Cerebral Cortical Synaptosomes

Inhibiting the excessive release of glutamate in the brain is emerging as a promising therapeutic option and is efficient for treating neurodegenerative disorders. The aim of this study is to investigate the effect and mechanism of plantainoside D (PD), a phenylenthanoid glycoside isolated from Plantago asiatica L., on glutamate release in rat cerebral cortical nerve terminals (synaptosomes). We observed that PD inhibited the potassium channel blocker 4-aminopyridine (4-AP)-evoked release of glutamate and elevated concentration of cytosolic Ca²⁺. Using bafilomycin A1 to block glutamate uptake into synaptic vesicles and EDTA to chelate extracellular Ca²⁺, the inhibitory effect of PD on 4-AP-evoked glutamate release was prevented. In contrast, the action of PD on the 4-AP-evoked release of glutamate in the presence of dl-TBOA, a potent nontransportable inhibitor of glutamate transporters, was unaffected. PD does not alter the 4-AP-mediated depolarization of the synaptosomal membrane potential, suggesting that the inhibitory effect of PD on glutamate release is associated with voltage-dependent Ca²⁺ channels (VDCCs) but not the modulation of plasma membrane potential. Pretreatment with the Ca²⁺ channel blocker (N-type) ω-conotoxin GVIA abolished the inhibitory effect of PD on the evoked glutamate release, as did pretreatment with the protein kinase C inhibitor GF109203x. However, the PD-mediated inhibition of glutamate release was eliminated by applying the mitochondrial Na⁺/Ca²⁺ exchanger inhibitor CGP37157 or dantrolene, which inhibits Ca²⁺ release through ryanodine receptor channels. These data suggest that PD mediates the inhibition of evoked glutamate release from synaptosomes primarily by reducing the influx of Ca²⁺ through N-type Ca²⁺ channels, subsequently reducing the protein kinase C cascade.

Gingerol Synergizes the Cytotoxic Effects of Doxorubicin against Liver Cancer Cells and Protects from Its Vascular Toxicity

Hydroxyphenylalkanes and diarylheptanoids possess potential therapeutic value in different pathophysiological conditions, such as malignancy. In the current study, naturally isolated hydroxyphenylalkane and diarylheptanoid compounds were investigated for potential chemo-modulatory effects in addition to potential vascular protective roles with doxorubicin. Diarylheptanoids showed stronger antioxidant effects, in comparison to hydroxyphenylalkanes, as demonstrated by DPPH assay and amelioration of CCl₄-induced disturbed intracellular GSH/GSSG balance. Shogaol and 4′-methoxygingerol showed considerable cytotoxic effects against HCT116, HeLa, HepG2 and MCF7 cells, with IC₅₀ values ranging from 3.1 to 19.4 µM. Gingerol significantly enhanced the cytotoxic profile of doxorubicin against HepG₂ and Huh7, cells decreasing its IC₅₀s by 10- and 4-fold, respectively. Cell cycle distribution was studied using DNA cytometry. Doxorubicin alone induced cell accumulation at S-phase and G₂/M-phase, while in combination with gingerol it significantly induced cell cycle arrest at the G₂/M-phase. Additionally, the vascular protective effect of gingerol against doxorubicin (10 µM) was examined on isolated aortic rings. Co-incubation with 6-gingerol (30 µM) completely blocked the exaggerated vasoconstriction and impaired vascular relaxation induced by doxorubicin. In conclusion, despite its relatively weak antioxidant properties, gingerol protected from DOX-induced vascular damage, apparently not through a ROS scavenging mechanism. Besides, gingerol synergized the cytotoxic effects of DOX against liver cancer cells without influencing the cellular pharmacokinetics.

Cytotoxic activity of hirsutanone, a diarylheptanoid isolated from Alnus glutinosa leaves

BACKGROUND

The low efficacy of cancer therapy for the treatment of patients with advanced disease makes the development of new anticancer agents necessary. Because natural products are a significant source of anticancer drugs, it is important to explore cytotoxic activity of novel compounds from natural origin.

PURPOSE

The aim of this work is to evaluate the cytotoxic capacity of hirsutanone, a diarylheptanoid isolated from Alnus glutinosa leaves. Hirsutanone cytotoxic way of action was also studied.

MATERIAL AND METHODS

The cytotoxic ability of Alnus glutinosa leaves ethyl acetate extract was studied over HeLa and PC-3 cell lines, with the MTT colorimetric assay. Hirsutanone was isolated from this extract using chromatographic methods, and its structure elucidated by spectroscopic analysis. HT-29 cell viability after hirsutanone treatment was determined using SRB assay. In order to understand hirsutanone way of action, cytotoxicity was evaluated adding the diarylheptanoid and antioxidants. DNA topoisomerase II (topo II) poison activity, was also evaluated using purified topo II and a supercoiled form of DNA that bears specific topo II recognition and binding region; topo II poisons stabilize normally transient DNA-topo II cleavage complexes, and lead an increased yield of linear form as a consequence of a lack of double-strand breaks rejoining.

RESULTS

The diarylheptanoid hirsutanone was isolated from Alnus glutinosa (L.) Gaertn. (Betulaceae) leaves extract that showed cytotoxic activity against PC-3 and HeLa cell lines. Hirsutanone showed cytotoxic activity against HT-29 human colon carcinoma cells. Pre-treatment with the antioxidants NAC (N-acetylcysteine) and MnTMPyP (Mn(III)tetrakis-(1-methyl-4-pyridyl)porthyrin) reduced this activity, suggesting that reactive oxygen species (ROS) participate in hirsutanone-induced cancer cell death. Using human topo II and a DNA supercoiled form, hirsutanone was found to stabilize topo II-DNA cleavage complexes, acting as a topo II poison.

CONCLUSION

Our data suggest that, like curcumin, an induction of oxidative stress and topo II-mediated DNA damage may play a role in hirsutanone-induced cancer cell death. Since both compounds share similar structure and cytotoxic profile, and curcumin is in clinical trials for the treatment of cancer, our results warrant further studies to evaluate the anticancer potential of hirsutanone.

Diarylheptanoids from the bark of black alder inhibit the growth of sensitive and multi-drug resistant non-small cell lung carcinoma cells

An extended study of minor diarylheptanoids from the bark of black alder has resulted in the isolation of twenty diarylheptanoids, ten of which have not previously been reported (14-18, 20-24). The structures and configurations of all compounds were elucidated by NMR, HRESIMS, UV, IR, and CD. The anti-cancer potency of twenty diarylheptanoids and four previously isolated compounds (7, 10, 12, 13) was investigated in human non-small cell lung carcinoma cell lines (sensitive and multi-drug resistant variants) as well as in normal human keratinocytes. Diarylheptanoids with a p-coumaroyl group, 14 and 18, platyphylloside (1), platyphyllonol-5-O-β-D-xylopyranoside (2), alnuside B (4) and hirsutenone (9) exhibited strong anti-cancer activity, considerably higher than diarylheptanoid curcumin, which served as a positive control. Compounds 4, 9, 14, and 18 displayed significant selectivity towards the cancer cells. Structure/activity analysis of twenty-four closely related diarylheptanoids revealed a high dependence of cytotoxic action on the presence of a carbonyl group at C-3. Substitution of a heptane chain on C-5 and a number of hydroxyl groups in the aromatic rings also emerged as a significant structural feature that influenced their cytotoxic potential.

Diarylheptanoid glycosides from Tacca plantaginea and their effects on NF-κB activation and PPAR transcriptional activity

In the screening search for NF-κB inhibitory and PPAR transactivational agents from medicinal plants, a methanol extract of the whole plant of Tacca plantaginea and its aqueous fraction showed the significant activities. Bioassay-guided fractionation combined with repeated chromatographic separation of the aqueous fraction of the methanol extract of T. plantaginea resulted in the isolation of two new diarylheptanoid glycosides, plantagineosides A (1) and B (2), an unusual new cyclic diarylheptanoid glycoside, plantagineoside C (3), and three known compounds (4-6). Their structures were determined by extensive spectroscopic and chemical methods. Compounds 3-6 significantly inhibited TNFα-induced NF-κB transcriptional activity in HepG2 cells in a dose-dependent manner, with IC(50) values ranging from 0.9 to 9.4 μM. Compounds 1-6 significantly activated the transcriptional activity of PPARs in a dose-dependent manner, with EC(50) values ranging from 0.30 to 10.4 μM. In addition, the transactivational effects of compounds 1-6 were evaluated on three individual PPAR subtypes, including PPARα, γ, and β(δ). Compounds 1-6 significantly enhanced the transcriptional activity of PPARβ(δ), with EC(50) values in a range of 11.0-30.1 μM. These data provide the rationale for using T. plantaginea and its components for the prevention and treatment of inflammatory and metabolic diseases.

Diarylheptanoid Hirsutenoxime Inhibits Toll-Like Receptor 4-Mediated NF-κB Activation Regulated by Akt Pathway in Keratinocytes

Microbial products, including lipopolysaccharides, may be involved in the pathogenesis of inflammatory skin diseases. We examined the effect of hirsutenoxime on the Toll-like receptor 4-mediated activation of Akt and nuclear factor (NF)-κB in lipopolysaccharide-stimulated keratinocytes. Hirsutenoxime, a cell signaling Akt inhibitor, and Bay 11-7085, an inhibitor of NF-κB activation, attenuated the lipopolysaccharide-induced expression of Toll-like receptor 4, activation of NF-κB and Akt, and the production of chemokines and reactive oxygen/nitrogen species. Hirsutenoxime may reduce the Toll-like receptor 4 expression-mediated NF-κB activation, which is regulated by the Akt pathway in keratinocytes exposed to lipopolysaccharides. This effect may reduce the skin inflammatory response.

Diarylheptanoid hirsutenone prevents tumor necrosis factor-alpha-stimulated production of inflammatory mediators in human keratinocytes through NF-kappaB inhibition

Keratinocytes may play an important role in the pathogenesis of skin disease in atopic dermatitis. Diarylheptanoids such as oregonin and hirstanonol are demonstrated to have anti-inflammatory and anti-oxidant effects. The present study was to investigate the effect of hirsutenone, one of the diarylheptanoids, against tumor necrosis factor (TNF)-alpha-stimulated responses in human keratinocytes. Hirsutenone attenuated the TNF-alpha-induced production of cytokine IL-8, prostaglandin E(2) and chemokine CCL27, and the formation of reactive oxygen/nitrogen species in keratinocytes. Immunosuppressants (dexamethasone and cyclosporin A) inhibited the TNF-alpha-elicited formation of IL-8, prostaglandin E(2) and CCL27, but did not affect formation of reactive species. Bay 11-7085 (an inhibitor of NF-kappaB activation) and anti-oxidant N-acetylcysteine attenuated the TNF-alpha-induced formation of inflammatory mediators and reactive species. Hirsutenone, dexamethasone, cyclosporin A and Bay 11-7085 inhibited the TNF-alpha-induced phosphorylation of inhibitory kappaB and the activation of nuclear factor (NF)-kappaB. The results show that hirsutenone seems to reduce the TNF-alpha-stimulated production of inflammatory mediators in keratinocytes by suppressing the activation of NF-kappaB that may be mediated by reactive oxygen species. The findings suggest that hirsutenone may exert an inhibitory effect against the pro-inflammatory mediator-induced skin disease.

Determination of oregonin in Alnus plants and biological samples by capillary electrophoresis

Oregonin, existing primarily in the Alnus plants, displayed anti-inflammatory and antioxidative activities. The capillary zone electrophoresis (CZE) method was developed in this study to quantitatively determine oregonin content in the Alnus plants for the first time. Various parameters, including buffer concentration, pH and applied voltage, were evaluated for their optimum analytical conditions. The optimized buffer was composed of 30 mM sodium tetraborate at pH 8.0. The separation voltage was set at 30 kV and the UV detection wavelength was set at 220 nm. Oregonin could be determined within 6 min under such optimized conditions. Relative standard deviation (R.S.D.) of the run-to-run repeatability and intermediate precision of the retention time of oregonin was within 1.36%. Run-to-run repeatability and intermediate precision of the peak area ratios of oregonin to internal standard, theophylline, were both within 1.55% R.S.D. The presented method was applied to analyze oregonin in leaves of Alnus formosana, seeds of various Alnus plants as well as biological samples. The stability of oregonin in biological system was indicated in this study. It demonstrates the potential of this developed method in natural product research.

Bioactivity of Hirsutanolol, Oregonin and Genkwanin, Isolated from the Seeds of Alnus Glutinosa (Betulaceae)

The antibacterial and free radical scavenging activity, and the general toxicity of two diarylheptanoids, hirsutanolol (1) and oregonin (2), and a flavonoid, genkwanin (3), isolated from the methanol extract of the seeds of Alnus glutinosa, were assessed by the 96 well-based serial dilution antibacterial assay using resazurin as an indicator of cell growth, the DPPH assay, and the brine shrimp lethality assay, respectively.

Synthesis of 1,7-bis(4-hydroxypenyl)-4-hydroxy-1,3-heptadiene-5-one, an antiplatelet diarylheptanoid from Alpinia blepharocalyx K. schum

A general and staight forward total synthesis of 1,7-bis(4-hydroxyphenyl)-3-hydroxy-1,3-heptadiene-5-one (5) starting from 4-methoxycinnamic acid (6) via ethyl 5-(4-methoxyphenyl)-3-hydroxy-2.4-pentadienoate (14) was accomplished in 19% overall yield.