Anup Sood

Boron analogues of amino acids VI. Synthesis and characterization of di- and tripeptide analogues as antineoplastic, anti-inflammatory and hypolipidemic agents

Abstract A number of boron-containing dipeptides with the general formulation Me 3 NBH 2 C(O)NHCH(R)COOR′ and a tripeptide, Me 3 NBH 2 C(O)NHCH 2 C(O)NHCH 2 COOEt were synthesized by condensation of Me 3 NBH 2 COOH with the corresponding NH 2 CH(R)COOR′ (NH 2 CH 2 C(O)NHCH 2 COOEt in case of tripeptide) in the presence of PPh 3 and CCl 4 . Further reaction with liquid NH 3 afforded NH 3 BH 2 C(O)NHCH(R)CONH 2 (NH 3 BH 2 C(O)NHCH 2 C(O)NHCH 2 C(O)NH 2 in the case of tripeptide) or NH 3 BH 2 C(O)NHCH(R)COOMe. These peptides proved to have antineoplastic, anti-inflammatory and hypolipidemic activity in mice. The antineoplastic activity was weak. The anti-inflammatory activity was similar to that of phenylbutazone, although at a lower dosage, ie 8 mg/kg × 2 was required for activity. IC 50 values were in the range of 7.0–29.0 mg/kg × 2. The compounds were most effective as hypolipidemic agents, significantly lowering both serum cholesterol and triglyceride levels at a dose of 8 mg/kg per day. After 16 days administration, this activity was far superior to known clinical therapeutic agents used to treat atherosclerosis.

Hypolipidemic activity of boronated nucleosides and nucleotides in rodents

Base-boronated nucleoside and phosphate-boronated nucleotides were potent hypolipidemic agents in rodents, lowering both serum cholesterol and triglyceride levels. Rat VLDL and LDL cholesterol levels were generally reduced and HDL cholesterol levels were significantly elevated after 14 days dosing at 8 mg/kg/day. Tissue cholesterol, triglyceride and phospholipid levels were reduced by selected derivatives. Increased fecal excretion of lipids did not appear to be a mechanism by which these derivatives lowered serum lipids in rodents. Rather, the agents suppressed appetite and reduced the activities of rate-limiting enzymes for de novo lipid synthesis, specifically cytoplasmic acetyl CoA synthetase, squalene synthetase, and phosphatidylate phosphohydrolase with IC50 values of approximately 10(-5) m.

Boron Containing Nucleic Acids

The radiobiological effectiveness of the neutron capture reaction is thought to be twice as great if it occurs in the cell nucleus rather than in the cytoplasm.1.2 To enhance the probability of localization in the cell nucleus, we have been carrying out the synthesis of a variety of boronated nucleic acids.

Boron analogues of phosphonoacetates: Synthesis, characterization and antitumor properties of sodium diethylphosphite-carboxyborane and related compounds

Abstract Several methods have been investigated for the synthesis of functionalized phosphite-borane adducts. As part of these investigations, the monosodium salt of diethylphosphite-carboxyborane (a boron analogue of sodium diethylphosphonoacetate) and related precursors and derivatives have been prepared. A brief description of their cytotoxic and antitumor properties is also presented.

The antineoplastic activity of trimethylamine carboxyboranes and related esters and amides in murine and human tumor cell lines.

Trimethylamine carboxyboranes including their esters and amides were shown to have antineoplastic activity in vivo against Ehrlich ascites carcinoma growth. The derivatization to the ester or amide did not necessarily improve activity. Cytotoxicity of the derivatives was observed against the growth of murine and human tumor cells. Selectivity was demonstrated by the boron derivatives in the human solid tumor screens. Almost all the compounds demonstrated cytotoxicity against single-cell suspension growths, eg Tmolt3, L1210, HeLa-S3. Selection of two compounds to examine their mode of action in L1210 lymphoid leukemia cells showed that the agents perferentially inhibited DNA synthesis followed by protein and RNA synthesis. The d(TTP) pools were markedly reduced because of inhibition of nucleotide kinase activity. The agents also inhibited regulatory enzymes in the de novo purine pathway and afforded DNA strand scission. These effects by the agents were probably additive to bring about tumor cell death.

Hypolipidaemic activity in rodents of boron analogs of phosphonoacetates and cyanoborane adducts of dialkyl aminomethylphosphonates

Boron analogues of phosphonoacetates proved to be potent hypolipidaemic agents in rodents, lowering both serum cholesterol and triglyceride levels. (C2H5O)3PBH2COOCH3 proved to be the most effective agent in mice, lowering serum cholesterol 46% and serum triglycerides 54% after 16 days. (C2H5O)3PBH2COOH and Na+H+(C2H5O)2(-O)PBH2COO- caused greater than a 40% reduction in lipids. The cyanoborane adducts of aminomethylphosphonates were generally less effective; (C6H5O)2P(O)CH2NH2BH2CN was the most effective, lowering serum cholesterol 32% and serum triglycerides 43% after 16 days. The phosphonoacetates appeared to lower lipid concentrations by several mechanisms. First, they lowered the de novo synthesis of cholesterol and triglycerides in the liver. Second, they accelerated the excretion of lipids into the bile and faeces. Thirdly, they modulated LDL and HDL-cholesterol contents in a manner which suggests they reduced the deposition of lipids in peripheral tissues, and accelerated the movement of cholesterol from tissues (e.g. plaques) to the liver for excretion into the bile.

The Effects of Amine-Carboxyborane Related Derivatives on UMR-106 Bone Metabolism.

The amine-carboxyboranes and related derivatives have been shown to be potent anti-inflammatory and anti-osteoporosis agents. Their action in part appears to be mediated by the modulation of cytokines, e.g. TNFα or IL-1. Previous studies have demonstrated that LPS induced macrophages release of TNFα maximally at 60 to 90 min. and IL-1 from 5 to 8 hr. The amine-carboxyboranes reduced significantly the release of these cytokines but also blocked TNFα high affinity binding to UMR-106 receptor at 90 min. at 10 μM, and IL-1 high affinity binding at 5 hr. at 12.5 μM. In addition, the agents suppressed IL-8 binding to CHO K1 high affinity receptor at 24 hr. at 50 μM and IL-2 binding to HuT-8 receptors at 25 μM at 90 min. and 5 hr. Correlation of metabolic events associated with osteoporosis showed that at 90 min., when TNFα receptor binding was reduced by the agents, calcium uptake into UMR-106 cells was reduced at 10 μM as well as the acid and alkaline phosphatases, and the prostaglandin cyclo-oxygenase activities and adhesion of leukocytes and macrophages to UMR-106 cell monolayers. At 5hr. when the agents reduced IL-1 binding to UMR-106 receptors, calcitonin and 1,25-dihydrovitamin D3 binding was reduced by the agents as was acid and alkaline phosphatase, and 5′-lipoxygenase activities and white blood cell adhesion. At this time calcium uptake and proline incorporation was increased significantly by the agents. At later times e.g. 18-48 hr. calcium uptake was still increased, and NAG activity was inhibited in the presence of the agents. These effects may be related more to the inhibition of other cytokine receptor binding, e.g. IL-8. Thus, many of the observed metabolic effects of amine-carboxyboranes as antiosteoporosis agents can be correlated with their inhibition of cytokine high affinity binding to target cell receptors.

DNA interaction with metal complexes and salts of substituted boranes and hydroborates in murine and human tumor cell lines.

A series of metal complexes and sodium salts of substituted boranes and hydroborates was shown to have cytotoxicity in murine and human tumor screens. Most of these agents were active against the growth of L-1210, Tmolt3 and Hela-S3. Selected agents demonstrated activity against the growth of monolayer human cell lines derived from solid tumors. Interestingly, many of the compounds demonstrated even lower ED50 values in the solid tumor than the L-1210 leukemic screen. Four compounds, Cu2(m-CH3)3NBH2CO2)4.2(CH3)NBH2COOH (I), [Fe3O((CH3)3NBH2CO2)6(CH3OH)3]NO3.CH3CN (II), cis-[Co(en)2((CH3)3N.BH2CO2)2]Cl.2.5 H2O.0.5 CH3OH (V), and Na(CH3)3NBH2CO2.0.25 CH3OH (IX) were shown preferentially to inhibit DNA synthesis of L-1210 cells with only moderate inhibition of RNA and protein synthesis. In preliminary studies these agents effectively inhibited the activities of regulatory enzymes involved in the purine pathway and nucleoside kinases resulting in the suppression of d(NTP) pool levels. The boron derivatives also caused L-1210 DNA strand scission. These drugs may act together to inhibit DNA synthesis and induce cytotoxicity.

Boronated pyrimidines and purines as cytotoxic, hypolipidemic and anti-inflammatory agents.

The simple boronated bases, e.g. cytosine, adenine and guanine, containing no sugar residues retained good pharmacological activity as hypolipidemic, anti-neoplastic and anti-inflammatory agents in mice at 8 mg/kg. Their activities were generally identical to their respective nucleoside derivatives. Interestingly the boronated acyclovir derivative was a very potent hypolipidemic agent achieving better activity than clofibrate and lovastatin. The boronated adenine derivatives appeared to have the best anti-inflammatory activity in reducing local edema and analgesic effects. The agents were active against the growth of murine and human leukemias and human HeLa-S3 suspended uterine carcinoma. Only the boronated adenine derivatives were effective in blocking the growth of human SW480 adenocarcinoma and the KB nasopharynx.

The Hypolipidemic and Anti-Inflammatory Activity of BoronatedAromatic Amino Acids in CF1 Male Mice

The boronated aromatic amino acids were shown to be potent hypolipidemic agents in mice lowering both serum cholesterol and triglycerides after 16 days. Selective compounds were as effective as the clinical standards. Furthermore, the compounds were effective anti-inflammatory agents reducing local and central pain as well as suppressing LPS induced endotoxic shock in mice. These agents inhibited lysosomal and proteolytic enzymes of the liver and macrophages as a part of their mechanism of action.