In vitro anti-Acanthamoeba activity of flavonoid glycosides isolated from Delphinium gracile, D. staphisagria, Consolida oliveriana and Aconitum napellus.

Acanthamoeba spp. are widely distributed in the environment and cause serious infections in humans. Treatment of Acanthamoeba infections is very challenging and not always effective which requires the development of more efficient drugs against Acanthamoeba spp. The purpose of the present study was to test medicinal plants that may be useful in the treatment of Acanthamoeba spp. Here we evaluated the trophozoital and cysticidal activity of 13 flavonoid glycosides isolated from Delphinium gracile, D. staphisagria, Consolida oliveriana and from Aconitum napellus subsp. Lusitanicum against the amoeba Acanthamoeba castellanii. AlamarBlue Assay Reagent® was used to determine the activity against trophozoites of A. castellanii, and cytotoxic using Vero cells. Cysticidal activity was assessed on treated cysts by light microscopy using a Neubauer chamber to quantify cysts and trophozoites. Flavonoids 1, 2, 3 and 4 showed higher trophozoital activity and selectivity indexes than the reference drug chlorhexidine digluconate. In addition, flavonoid 2 showed 100% cysticidal activity at a concentration of 50 µm, lower than those of the reference drug and flavonoid 3 (100 µm). These results suggest that flavonoids 2 and 3 might be used for the development of novel therapeutic approaches against Acanthamoeba infections after satisfactory in vivo evaluations.

Astragalin heptaacetate-induced cell death in human leukemia cells is dependent on caspases and activates the MAPK pathway.

Flavonoids are naturally occurring polyphenolic compounds and are among the most promising anticancer agents. Here we demonstrate that the flavonoid derivative astragalin heptaacetate (AHA) induces cell death. This was prevented by the non-specific caspase inhibitors z-VAD-fmk and Q-VD-OPH, and reduced by the selective caspase-4 inhibitor z-LEVD-fmk. AHA-induced cell death was found to be: (i) associated with the release of cytochrome c, (ii) suppressed by the overexpression of Bcl-x(L), (iii) amplified by inhibition of extracellular signal-regulated kinases (ERKs) 1/2 and c-jun NH(2)-terminal kinases/stress activated protein kinases (JNK/SAPK) signaling, and (iv) completely abrogated by the free-radical scavenger N-acetyl-l-cysteine.

Trifolin acetate-induced cell death in human leukemia cells is dependent on caspase-6 and activates the MAPK pathway.

In the present study we demonstrated that the flavonoid derivative trifolin acetate (TA), obtained by acetylation of naturally occurring trifolin, induces apoptosis. Associated downstream signaling events were also investigated. TA-induced cell death was prevented by the non-specific caspase inhibitor z-VAD-fmk and reduced by the presence of the selective caspase inhibitors z-LEHD-fmk (caspase-9), z-DEVD-fmk (caspase-3) and z-VEID-fmk (caspase-6). The apoptotic effect of TA was associated with (i) the release of cytochrome c from mitochondria which was not accompanied by dissipation of the mitochondrial membrane potential (DeltaPsi(m)), (ii) the activation of the mitogen-activated protein kinases (MAPKs) pathway and (iii) abrogated by the over-expression of Bcl-2 or Bcl-x(L). TA-induced cell death was attenuated by inhibition of extracellular signal-regulated kinases (ERK) 1/2 with U0126 and inhibition of p38(MAPK) with SB203580. In contrast, inhibition of c-Jun NH(2)-terminal kinase (JNK) by SP600125 significantly enhanced apoptosis. Although reactive oxygen species (ROS) increased in response to TA, this did not seem to play a pivotal role in the apoptotic process since different anti-oxidants were unable to provide cell protection. The present study demonstrates that TA-induced cell death is mediated by an intrinsic-dependent apoptotic event involving mitochondria and MAPK, and through a mechanism independent of ROS generation.

Cytotoxic activities of flavonoid glycoside acetates from Consolida oliveriana.

The flavonoids kaempferol, quercetin, trifolin, hyperoside 2''- and 6''- acetates, 7-glucotrifolin, biorobin and robinin were isolated from the aerial parts of Consolida oliveriana. Their derivatives kaempferol tetraacetate, quercetin pentaacetate, trifolin heptaacetate and hyperoside octaacetate exhibited significant cytotoxicity IN VITRO against three human cell lines HL-60, U937 and SK-MEL-1 while hyperoside 2''-acetate, hyperoside-6''-acetate, glucotrifolin decaacetate and heptamethyltrifolin were inactive.

In vitro activity of C20-diterpenoid alkaloid derivatives in promastigotes and intracellular amastigotes of Leishmania infantum.

The in vitro anti-proliferative effects are described of several atisine-type diterpenoid alkaloids against the protozoan parasite Leishmania infantum, which causes human visceral leishmaniasis and canine leishmaniasis in the Mediterranean basin, as well as human cutaneous leishmaniasis throughout the Mediterranean region. From a total of 43 compounds tested, including C19- and C20-diterpene alkaloids from several chemical classes, only 15,22-O-diacetyl-19-oxo-dihydroatisine, azitine and isoazitine were highly active against cultures of the parasite (promastigote form) with IC50 values within the range of the reference drug pentamidine-isothionate (7.39-12.80 mg/L for the test compounds, 11.32 mg/L for the positive control). These compounds were not toxic to the host cell. When treated with a dosage of 5 microg/mL of the active compounds (half of their IC50), the promastigote forms lost 80% of their infection capacity and the multiplication of extracellular forms of L. infantum was severely affected. The study showed that atisine-type C20-diterpenoid alkaloids exhibited promising anti-leishmanial properties with strong molecular selectivity. These might have implications for other intracellular pathogens- or phylogenetically related parasites, such as Trypanosoma spp.