Jiří Dohnal

Investigation of new acyloxy derivatives of cholic acid and their esters as drug absorption modifiers

Skin penetration enhancers are used in the formulation of transdermal delivery systems for drugs that are otherwise not sufficiently skin-permeable. Intestinal absorption promoters/enhancers are used as excipients in oral formulations of poorly oral-bioavailable drugs. Series of fourteen acyloxy derivatives of 5β-cholic acid as potential drug absorption modifiers was generated by multistep synthesis. The synthesis of all newly prepared compounds is presented here. Structure confirmation of all generated compounds was accomplished by (1)H NMR, (13)C NMR, IR and MS spectroscopy methods. All the prepared compounds were analyzed using RP-TLC, and their lipophilicity (R(M)) was determined. The hydrophobicity (logP) and solubility (logS) of the studied compounds were also calculated using two commercially available programs. All the target compounds were tested for their in vitro transdermal penetration activity and as potential intestinal absorption enhancers. The anti-proliferative activity of all the final compounds was also assessed against the human cancer cell lines: T-lymphoblastic leukemia cell line and the breast adenocarcinoma cell line. Their cytotoxicity was also evaluated against the normal human skin fibroblast cells. Two compounds showed anti-proliferative effect on cancer cells without affecting the growth of normal cells, which should be promising in potential development of new drugs. Most of the target compounds showed minimal anti-proliferative activity (IC(50)>37 μM), indicating they would have low cytotoxicity when administered as chemical absorption modifiers. The relationships between the lipophilicity and the chemical structure of the studied compounds as well as the relationships between their chemical structure and enhancement effects are discussed in this article.

New propanoyloxy derivatives of 5β-cholan-24-oic acid as drug absorption modifiers.

A series of final twelve propanoyloxy derivatives of 5β-cholan-24-oic acid (O-propanoyl derivatives of cholic acid) as potential drug absorption modifiers (skin penetration enhancers, intestinal absorption promoters) was generated by multistep synthesis. Structure confirmation of all generated compounds was accomplished by 1H NMR, 13C NMR, IR and MS spectroscopy methods. All the prepared compounds were analyzed using RP-TLC, and their lipophilicity (RM) was determined. The hydrophobicity (log P), solubility (log S), polar surface area (PSA) and molar volume (MV) of the studied compounds were also calculated. All the target compounds were tested for their in vitro transdermal penetration effect and as potential intestinal absorption enhancers. The cytotoxicity of all the evaluated compounds was evaluated against normal human skin fibroblast cells. Their anti-proliferative activity was also assessed against human cancer cell lines: T-lymphoblastic leukemia cell line and breast adenocarcinoma cell line. One compound showed selective cytotoxicity against human skin fibroblast cells and another compound possessed the highest cytotoxicity against all the tested cell lines. Only one compound expressed anti-proliferative effect on leukemia cancer cells without affecting the growth of normal cells, which should be promising in potential development of new drugs. Most of the target compounds showed minimal anti-proliferative activity (IC50>37 μM), indicating they would have moderate cytotoxicity when administered as chemical absorption modifiers. The relationships between the lipophilicity/polarity and the chemical structure of the studied compounds as well as the relationships between their chemical structure and enhancement effect are discussed in this article.

Product of alaptide synthesis: Determination of the absolute configuration

Alaptide is the active substance of the veterinary dermatological ointment ALAPTID and a potential drug in human medicine. Electronic circular dichroism spectroscopy (ECD), transparent spectral region optical rotation (OR), and ab initio calculations were employed to determine the absolute configuration of alaptide. No X-ray structural data determining the absolute configuration were available. It was not possible to employ vibrational circular dichroism spectroscopy (VCD), because alaptide was not sufficiently soluble in common solvents used in VCD spectroscopy to generate reliable spectra. Both ECD spectra and OR values of alaptide solution were in good agreement with predicted data and determined unambiguously the absolute configuration of alaptide synthesized from (S)-alanine as being (S).

New polyfluorothiopropanoyloxy derivatives of 5β-cholan-24-oic acid designed as drug absorption modifiers

A series of final six propanoyloxy derivatives of 5β-cholan-24-oic acid (tridecafluoroctylsulfanyl- and tridecafluoroctylsulfinylethoxycarbonylpropanoyloxy derivatives) as potential drug absorption promoters (skin penetration enhancers, intestinal absorption promoters) was generated by multistep synthesis. Structure confirmation of all generated compounds was accomplished by (1)H NMR, (13)C NMR, IR and MS spectroscopy methods. All the prepared compounds were analyzed using RP-TLC, and their lipophilicity (RM) was determined. The hydrophobicity (log P), solubility (logS), polar surface area (PSA) and molar volume (MV) of the studied compounds were also calculated. All the target compounds were tested for their in vitro transdermal penetration effect and as potential intestinal absorption enhancers. The cytotoxicity of all the evaluated compounds was evaluated against normal human skin fibroblast cells. Their anti-proliferative activity was also assessed against human cancer cell lines: T-lymphoblastic leukaemia cell line and breast adenocarcinoma cell line. One compound showed high selective cytotoxicity against human skin fibroblast cells and another compound possessed high cytotoxicity against breast adenocarcinoma cell line and skin fibroblast cells. Only one compound expressed anti-proliferative effect on leukaemia and breast adenocarcinoma cells without affecting the growth of normal cells, which should be promising in potential development of new drugs. Most of the target compounds showed minimal anti-proliferative activity (IC50>37μM), indicating they would have moderate cytotoxicity when administered as chemical absorption modifiers. The relationships between the lipophilicity/polarity and the chemical structure of the studied compounds as well as the relationships between their chemical structure and penetration enhancement effect are discussed in this article.

Alaptide as Transdermal Permeation Modifier

Based on the fact that alaptide is able to influence the creation and function of keratinocytes, it was supposed that alaptide could be used as a transdermal permeation modifier. Various APIs (bases, acids, salts, neutral molecules, small molecules, steroid-like molecules) were tested on their transdermal permeation in the mixture with micronized and/or nanonized alaptide as a transdermal permeation modifier. Also the influence of the type of formulation (ointment, cream, gel) on the effect of alaptide on skin was investigated intensively. It was observed that under specific conditions alaptide is able to suppress permeation/absorption of compounds through the skin, which can limit the site of action of potentially hazardous/toxic drugs to skin surface. The skin curative activity of alaptide can be helpful in reduction of possible skin irritant/injurious effects of permeating compounds. In transdermal application alaptide causes an increase or a decrease, in dependence on the used concentration, physical state and supporting medium (pharmaceutical formulation), in permeation/absorption of drugs into the skin and/or through the skin. The concentration of the used drug was increased at the place of administration, and/or the systemic concentration was increased, or it was ensured that drugs acted only on the skin surface/in the skin surface layer and did not penetrate into the deeper skin layers or did not have any systemic effect. Although alaptide was found in the 1980s of the twentieth century, even now it has great potential either as an active pharmaceutical ingredient or a permeation modifier.