The chemical and biological potential of C ring modified triterpenoids

A convenient and elegant route has been developed to separate the natural regioisomers triterpenoids ursolic acid (UA) and oleanolic acid (OA) as well as derivatives thereof. Eleven unknown derivatives of OA were designed, synthesized, and their cytotoxicity was investigated. Further sixteen compounds were prepared to correlate all compounds in a SAR study. It could be shown that C-ring modifications of OA and UA have only a moderate influence onto the cytotoxic activity of the compounds but a significant impact onto the ability to trigger apoptosis in ovarian cancer cells (cell line A2780).

Targeting cancer cells with oleanolic and ursolic acid derived hydroxamates

Oleanolic and ursolic acid derived hydroxamates were easily obtained from their parent compounds; they were screened for their cytotoxicity applying SRB assays employing several human tumor cell lines. Low EC50 values were determined for compounds in which the nitrogen as well as the oxygen in the hydroxamic acid part still holds acidic hydrogens. Thus, ursolic acid derived compounds having at least an OH and/or NH moiety in the hydroxamate part of the molecule showed good cytotoxicity but they are significantly less selective for the tumor cells than oleanolic acid derived compounds. Good results were determined for oleanolic acid derived 7 for tumor cell lines 518A2 (melanoma, EC50=3.3 μM), A2780 (ovarian carcinoma, EC50=3.4 μM) and HT29 (colon adenocarcinoma, EC50=5.6 μM) while being significantly less cytotoxic for fibroblasts (EC50=20.4 μM).

Transformation of asiatic acid into a mitocanic, bimodal-acting rhodamine B conjugate of nanomolar cytotoxicity

Based on their biological activity natural products continue to represent optimal lead structures for the development of novel drug candidates. We focused on the syntheses of several derivatives of the triterpene asiatic acid and on the evaluation of their cytotoxic activity in a photometric sulforhodamin B assay. Especially, benzamide 2 and rhodamine B conjugate 11 show a distinct cytotoxicity for several human tumor cell lines, e.g. EC₅₀ (A2780) = 110 ± 1 nM and EC₅₀ (A2780) = 8 ± 2 nM, respectively. Interestingly, compound 11 showed for two human tumor cell lines (HT29 and 518A2) non-linear, bimodal dose-response relationships.

Novel dehydroabietylamine derivatives as potent inhibitors of acetylcholinesterase

Nowadays, the inhibition of acetylcholinesterase is one of the main pharmacological strategies for the treatment of Alzheimer's disease. Therefore, a set of thirty-four derivatives of the diterpenoid dehydroabietylamine has been synthesized and screened in colorimetric Ellman's assays to determine their ability to inhibit the enzymes acetylcholinesterase (AChE, from electric eel) and butyrylcholinesterase (BChE, from equine serum). A systematic variation of the substitution of dehydroabietylamides enabled an approach to analogs showing a remarkable inhibition potency for AChE. Particularly N-benzoyldehydroabietylamines 11, 12 and 13 were excellent inhibitors for AChE, showing inhibition rates comparable to standard galantamine hydrobromide.

Synthesis and proapoptotic activity of oleanolic acid derived amides

Thirty-one different 3-O-acetyl-OA derived amides have been prepared and screened for their cytotoxic activity. In the SRB assays nearly all the carboxamides displayed good cytotoxicity in the low μM range for several human tumor cell lines. Low EC50 values were obtained especially for the picolinylamides 14-16, for a N-[2-(dimethylamino)-ethyl] derivative 27 and a N-[2-(pyrrolinyl)-ethyl] carboxamide 28. These compounds were submitted to an extensive biological testing and proved compound 15 to act mainly by an arrest of the tumor cells in the S phase of the cell cycle. Cell death occurred by autophagy while compounds 27 and 28 triggered apoptosis.

Piperlongumine B and analogs are promising and selective inhibitors for acetylcholinesterase

Piperlongumine B (19), an alkaloid previously isolated from long pepper (Piper longum) has been synthesized for the first time in a short sequence and in good yield together with 19 analogs. Screening of these compounds in Ellman's assays showed several of them to be good inhibitors of acetylcholinesterase while being less active for butyrylcholinesterase. Activity of the compounds increased with the ring size of the heterocycle, and a maximum of activity was observed for an analog holding 12 methylene groups in the aliphatic side chain. These compounds may be regarded as promising candidates for the development of efficient inhibitors of acetylcholinesterase being useful for the treatment of Alzheimer's disease.

Cytotoxic Dehydroabietylamine Derived Compounds

BACKGROUND AND METHODS

Chemotherapy remains one of the most important methods for the treatment of cancer. More recently in this context, some products derived from natural products have raised scientific interest which especially include many terpenes. Thereby, diterpenoids represent a special class, and within this class of important secondary natural products, especially compounds derived from Dehydroabietylamine (DA), are of particular interest.

RESULTS

This review not only gives a summary of the most important findings on the cytotoxic behavior of DAderived compounds but also shows some drawbacks of these compounds, such low bioavailability and/or poor solubility of several derivatives of DA. It focusses on the chemical aspects and summarizes the DA related biological effects without deep discussion of underlying biochemical pathways.

CONCLUSION

Dehydroabietylamine-derived cytotoxic compounds hold a high potential to be developed into efficient antitumor active drugs.

Unexpected AChE inhibitory activity of (2E)α,β-unsaturated fatty acids

A small library of (E) α,β-unsaturated fatty acids was prepared, and 20 different saturated and mono-unsaturated fatty acids differing in chain length were subjected to Ellman's assays to determine their ability to act as inhibitors for AChE or BChE. While the compounds were only very weak inhibitors of BChE, seven molecules were inhibitors of AChE holding IC₅₀ = 4.3-12.8 M with three of them as significant inhibitors of this enzyme. The results have shown trans 2-mono-unsaturated fatty acids are better inhibitors for AChE than their saturated analogs. Furthermore, the screening results indicate that the chain length is crucial for obtaining an inhibitory efficacy. The best results were obtained for (2E) eicosenoic acid (14) showing inhibition constants K_i = 1.51 ± 0.09 M and K_i' = 7.15 ± 0.55 M. All tested compounds were mixed-type inhibitors with a dominating competitive part. Molecular modelling calculations indicate a different binding mode of active/inactive compounds for the enzymes AChE and BChE.

Differential T4 degradation pathways in young patients with preterminal and terminal renal failure

INTRODUCTION

The aim of this study is to analyze thyroid hormone parameters in large homogenous patient cohorts with preterminal (stage 4) and terminal (stage 5) renal failure in an area of low iodine intake.

PATIENTS AND METHODS

Thyroid parameters were measured in healthy controls (n=48), patients with preterminal renal failure (n=48) and patients with terminal renal failure undergoing hemodialysis (n=288). All patients were assessed by measurement of TSH, T4, T3, fT4, rT3, Tg and TPO-antibodies.

RESULTS

There was a significant decrease of T4 and fT4 from healthy controls to patients with preterminal renal failure and to patients with terminal renal failure. T3 showed a decrease from healthy controls to patients with preterminal renal failure and to patients with terminal renal failure (1.54+/-0.06 microg/l VS. 1.05+/-0.05 microg/l VS. 1.09+/-0.23 microg/l, p<0.001 VS. controls). rT3 was significantly decreased in patients with terminal renal failure (0.24+/-0.01 microg/l VS. 0.25+/-0.02 microg/l VS. 0.16+/-0.01 microg/l, p<0.001). The rT3/T3 ratio was significantly elevated in patients with preterminal renal failure (p<0.01). TSH concentrations were in the normal range in all groups.

CONCLUSION

Our data suggest different T4 degradation pathways in patients with preterminal and terminal renal failure.

A bioassay-driven discovery of an unexpected selenophene and its cytotoxicity

During the reaction of methyl 3β-acetoxy-glycyrrhetinate (1) with SeO2 significant amounts of a cytotoxic hitherto unprecedented triterpenoic selenophene 3 are formed. This compound stops cell proliferation and acts by apoptosis.

[Familial Mediterranean fever]

BACKGROUND

Familial Mediterranean fever (FMF) is characterized by febrile attacks, acute abdominal pain, pleuritis or arthritis and predominantly observed in ethnic groups of the Mediterranean area (Sephardic Jews, Turks, Armenians). Its most ominous manifestation is amyloidosis potentially leading to chronic renal failure. FMF is an inherited disorder caused by mutations of the FMF-gene, which first was described in 1997.

CASE REPORT

We report a 10-year old turkish boy and his family presenting with an increased blood sedimentation rate (WBC) and recurrent attacks of acute abdominal pain. A molecular analysis was carried out, confirming a typical mutation of the FMF-gene. The patient remained free of symptoms after starting therapy with colchicine.

CONCLUSION

Investigation of the FMF gene enables an early diagnosis in case of clinical suspect findings, subsequent colchicine administration may prevent amyloidosis.

[Sleep disorders in patients with dialysis-dependent renal failure]

A questionnaire was performed in order to classify the prevalence of sleep disorders in patients with end-stage renal disease treated with hemodialysis. 69 patients (41 male, 28 female) with a median age of 57 years completed the questionnaire. 67% of these patients complained of sleep disorders. 31 patients (45%) had evidence of periodic leg movement syndrome, 22 patients (32%) of restless legs syndrome. 29 patients (42%) had difficulties in falling asleep, 27 patients (39%) in maintaining sleep and 17 (25%) experienced both. Snoring was found in 25 patients (36%), 13 patients (19%) seemed to have sleep apnea. These data show an increased prevalence of sleep disorders in patients with end-stage renal disease on hemodialysis treatment. We conclude that these patients should consequently be asked for sleep disorders, as a specific diagnostic and therapeutic regime could improve quality of life and life expectancy. Especially sleep apnea is a disease that has a high prevalence in this patient group and which can be treated successfully.

[Value of transtracheal oxygen insufflation in the weaning period after long-term ventilation]

BACKGROUND

In many cases, respiratory muscle failure is the reason for unsuccessful weaning attempts after long-term ventilation. Therapeutic measures must therefore be aimed at unloading the respiratory pump. In this present study we examined whether, in particular, the transtracheal O2-insufflation (TTO2) results in a change of breathing patterns and unloads the respiratory muscles.

PATIENTS AND METHODS

We examined 6 patients (5 males, age 65.6 +/- 3.9 years, diagnosis: chronic obstructive lung disease), who received long-term mechanical ventilation in outward intensive care units. Baseline resting data (arterial blood gas analysis, the breathing frequency and the minute volume) were obtained with the patients breathing room air for 1 hour. After receiving TTO2 with a flow of 21/min for another 1-hour-period the measurements were repeated.

RESULTS AND CONCLUSION

In our study we could show that the TTO2 leads to an impressive decrease in inspiratory work of breathing-relative to the minute ventilation by about 28%. Therefore TTO2 is of great importance in the weaning phase subsequent to prolonged mechanical ventilation due to the respiratory muscle failure.