Cytotoxic and antiproliferative effects of heptaacetyltiliroside on human leukemic cell lines

Silencing of caveolin-1 in fibroblasts as opposed to epithelial tumor cells results in increased tumor growth rate and chemoresistance in a human pancreatic cancer model

Caveolin-1 (Cav-1) expression has been shown to be associated with tumor growth and resistance to chemotherapy in pancreatic cancer. The primary aim of this study was to explore the significance of Cav-1 expression in pancreatic cancer cells as compared to fibroblasts in relation to cancer cell proliferation and chemoresistance, both in vitro and in vivo, in an immunodeficient mouse model. We also aimed to evaluate the immunohistochemical expression of Cav-1 in the epithelial and stromal component of pancreatic cancer tissue specimens. The immunohistochemical staining of poorly differentiated tissue sections revealed a strong and weak Cav-1 expression in the epithelial tumor cells and stromal fibroblasts, respectively. Conversely, the well-differentiated areas were characterized by a weak epithelial Cav-1 expression. Cav-1 downregulation in cancer cells resulted in an increased proliferation in vitro; however, it had no effect on chemoresistance and growth gain in vivo. By contrast, the decreased expression of Cav-1 in fibroblasts resulted in a growth advantage and the chemo-resistance of cancer cells when they were co-injected into immunodeficient mice to develop mixed fibroblast/cancer cell xenografts. On the whole, the findings of this study suggest that the downregulation of Cav-1 in fibroblasts is associated with an increased tumor proliferation rate in vivo and chemoresistance. Further studies are warranted to explore whether the targeting of Cav-1 in the stroma may represent a novel therapeutic approach in pancreatic cancer.

A Review on the Dietary Flavonoid Tiliroside

Among flavonoid derivatives, tiliroside is a flavonoid contained in several edible plants or specific plant parts (fruits, leaves, or roots). These parts are often widely used as both food and medicines, in the treatment of various ailments and, in some cases, as food supplements. Considering the easy access to many publications concerning tiliroside and the lack of a review that summarizes the current progress in studies on its safety, efficacy, and presence in the plant kingdom, we present here a review paper on tiliroside and its principal derivatives. The paper also highlights the basic knowledge regarding this molecule, its derivatives, and the analytical approaches used for extraction and quantification, as well as reports on the biological activities against different key enzymes linked to various human diseases. The reported information is also devoted to highlighting the concept "learn from nature to discover new products," particularly in the development of new drugs, food supplements, and nutraceuticals, starting from a natural lead compound such as tiliroside and improving its biological activities (and selectivities) against a specific target for therapeutic purposes.

New Sulphated Flavonoids from Wissadula periplocifolia (L.) C. Presl (Malvaceae)

Wissadula periplocifolia (L.) C. Presl (Malvaceae) is commonly used in Brazil to treat bee stings and as an antiseptic. The antioxidant properties of its extracts have been previously demonstrated, thus justifying a phytochemical investigation for its bioactive phenolic constituents. This has yielded five new sulphated flavonoids: 8-O-sulphate isoscutellarein (yannin) (1a); 4′-O-methyl-7-O-sulphate isoscutellarein (beltraonin) (1b); 7-O-sulphate acacetin (wissadulin) (2a); 4′-O-methyl-8-O-sulphate isoscutellarein (caicoine) (2b) and 3′-O-methyl-8-O-sulphate hypolaetin (pedroin) (3b) along with the known flavonoids 7,4′-di-O-methyl-8-O-sulphate isoscutellarein (4), acacetin, apigenin, isoscutellarein, 4′-O-methyl isoscutellarein, 7,4′-di-O-methylisoscutellarein, astragalin and tiliroside. The compounds were isolated by column chromatography and identified by NMR (¹H, ¹³C, HMQC, HMBC and COSY) and LC-HRMS. A cell based assay was carried out to evaluate the preliminary cytotoxic properties of the flavonoids against UVW glioma and PC-3M prostate cancer cells as well as non-tumour cell lines. The obtained results showed that acacetin, tiliroside, a mixture of acacetin + apigenin and the sulphated flavonoids 2a + 2b exhibited inhibitory activity against at least one of the cell lines tested. Among the tested flavonoids acacetin and tiliroside showed lower IC₅₀ values, presenting promising antitumor effects.

In vitro activity of dietary flavonol congeners against human cancer cell lines

BACKGROUND

Flavonoids have physiological activity and a variety of pharmacological properties, including anticancer activity in vitro, but structure-anticancer activity relationships are unclear.

AIM

The objectives of this work were to investigate the activity of dietary flavonol congeners against cell lines derived from human solid tumours and to examine whether the in vitro activity was associated with specific structural feature(s) of the molecules.

METHODS

Antiproliferative activity of the flavonol congeners was investigated against eight different human cancer cell lines representing different types of human solid tumour, using the sulforhodamine B (SRB) assay in accordance with the instructions published by the NCI. Cell cycle perturbations caused by the congeners were monitored by flow-cytometric analysis of DNA stained with propidium iodide.

RESULTS

Most of the flavonols examined had weak antiproliferative and cytotoxic activity. Of all the flavonol congeners tested peracetylated tiliroside found to be the most powerful, with significant antiproliferative and cytotoxic activity. Most flavonols induced similar cell cycle perturbations, whereas induction of apoptosis was significant only for cells treated with peracetylated tiliroside.

CONCLUSIONS

These findings indicated that the -OH groups of aromatic ring B were not linked to the cytotoxic and antiproliferative activity of the tested flavonols whereas peracetylation of the glycosides resulted in moderate improvement. In contrast, acetylation of tiliroside esterified with coumaric acid at position 5 of the sugar moiety greatly improved the activity of this congener. Overall, the results of this study suggest a critical role of sugar moiety substituents in the anticancer activity of the flavonols.

Protective and detrimental effects of kaempferol in rat H4IIE cells: Implication of oxidative stress and apoptosis

Flavonoids are ubiquitous substances in fruits and vegetables. Among them, the flavonol kaempferol contributes up to 30% of total dietary flavonoid intake. Flavonoids are assumed to exert beneficial effects on human health, e.g., anticancer properties. For this reason, they are used in food supplements at high doses. The aim of this project was to determine the effects of kaempferol on oxidative stress and apoptosis in H4IIE rat hepatoma cells over a broad concentration range. Kaempferol is rapidly taken up and glucuronidated by H4IIE cells. The results demonstrate that kaempferol protects against H2O2-induced cellular damage at concentrations which lead to cell death and DNA strand breaks in the absence of H2O2-mediated oxidative stress. Preincubation with 50 microM kaempferol exerts protection against the loss of cell viability induced by 500 microM H2O2 (2 h) while the same concentration of kaempferol reduces cell viability by 50% in the absence of H2O2 (24 h). Preincubation with 50 microM kaempferol ameliorates the strong DNA damage induced by 500 microM H2O2 while 50 microM kaempferol leads to a significant increase of DNA breakage in the absence of H2O2. Preincubation with 50 microM kaempferol reduces H2O2-mediated caspase-3 activity by 40% (4 h) while the same concentration of kaempferol leads to the formation of a DNA ladder in the absence of H2O2 (24 h). It is concluded that the intake of high dose kaempferol in food supplements may not be advisable because in our cellular model protective kaempferol concentrations can also induce DNA damage and apoptosis by themselves.

Encapsulation of naturally occurring flavonoids into liposomes: physicochemical properties and biological activity against human cancer cell lines

Liposomes consisting of egg phosphatidylcholine were prepared by a thin-film hydration method followed by sonication and were used to investigate the percentage encapsulation of four flavonoids (quercetin, rutin, isoscutellarein and isoscutellarein diglycoside). The lipid recovery and the flavonoid-to-lipid molar ratio were measured using high-performance thin-layer chromatography/flame ionization detection and UV-vis spectroscopy. Differential scanning calorimetry was used to study the effect of the flavonoids on the phase transition temperature and on the enthalpy of the main phase transition of dipalmitoylphosphatidylcholine bilayers, and their ability to influence the membrane fluidity. The final liposomal formulation incorporating flavonoids, as well as free flavonoids, were tested for their activity against human cancer cell lines using the sulforhodamine B assay. The results showed that the encapsulation efficiency varied from 95% (0.21 flavonoid-to-lipid molar ratio) to 37.5% (0.09 flavonoid-to-lipid molar ratio) for isoscutellarein and its glycoside, respectively. The differential scanning calorimetry data showed close thermal and dynamic effects depending on the structure of the flavonoids, and suggest that there is a relationship between flavonoid molecular structure and the interaction with model membranes. Liposomal isoscutellarein showed improved growth inhibiting activity against all cell lines tested in comparison with that of its free form, which was inactive (>100 microM).

Biological activity of myricetin and its derivatives against human leukemic cell lines in vitro

Two myricetin derivatives, the 3,7, 4('), 5(')- tetramethyl ether of myricetin (1), isolated from the hexane extract of Cistus monspeliensis, and its 3('),5-diacetyl derivative (2) which was synthesized, and the parent compound, myricetin (3), were examined for their in vitro cytotoxic activity against nine human leukemic cell lines, two of which were mdr cell lines. Compound 2 exhibited higher cytostatic and cytotoxic activities in comparison to compound 1, while compound 3 was inactive against all tested cell lines. Vinblastine was used as a control.