Effects of steroidal allenic phosphonic acid derivatives on the parasitic protists Leishmania donovani, Leishmania mexicana mexicana, and Pneumocystis carinii carinii

Steroid phosphate esters and phosphonosteroids and their biological activities

Steroid phosphate esters are very rare natural lipids that have been comparatively recently isolated from fractions of polar lipids of marine sponges and starfish. These steroids exhibit interesting biological activities. When using the PASS computer program, we showed that many of steroid phosphate esters showed antifungal, antihypercholesterolemic, anesthetic, and other activities with a confidence of 73 to 93%. In addition, some of them can be used as inhibitors of cholesterol synthesis and show hepatoprotection properties. Phosphonosteroids demonstrate antineoplastic and antihypercholesterolemic activities with a certainty of 85 to 90%. And also, they can be used as ovulation inhibitors or female steroid contraceptives with confidence from 86 to 98%.

Silver-catalyzed phosphonylation of unprotected propargylic alcohols for the synthesis of allenylphosphoryl compounds

A facile and efficient method for the synthesis of a variety of allenylphosphine oxides by silver-catalyzed phosphonylation of unprotected propargylic alcohols with P(O)H compounds has been established.

Allenic and cumulenic lipids

Nowadays, about 200 natural allenic metabolites, more than 2700 synthetic allenic compounds, and about 1300 cumulenic structures are known. The present review describes research on natural as well as some biological active allenic and cumulenic lipids and related compounds isolated from different sources. Intensive searches for new classes of pharmacologically potent agents produced by living organisms have resulted in the discovery of dozens of such compounds possessing high anticancer, cytotoxic, antibacterial, antiviral, and other activities. Known allenic and cumulenic compounds can be subdivided on several structural classes: fatty acids, hydrocarbons, terpenes, steroids, carotenoids, marine bromoallenes, peptides, aromatic, cumulenic, and miscellaneous compounds. This review emphasizes the role of natural and synthetic allenic and cumulenic lipids and other related compounds as an important source of leads for drug discovery.

Sterol metabolism in the opportunistic pathogen Pneumocystis: advances and new insights

Pneumocystis can transiently colonize healthy individuals without causing adverse symptoms, and most people test positive for exposure to this organism early in life. However, it can cause Pneumocystis pneumonia (PcP) in people with impaired immune systems and is a major cause of death in HIV/AIDS. Although it has close affinities to the Ascomycetes, Pneumocystis has features unlike those of any single group of fungi. For example, Pneumocystis does not synthesize ergosterol, which is consistent with the inefficacy of amphotericin B and some triazoles in clearing PcP. Pneumocystis sterols include distinct delta7 24-alkylsterols. Metabolic radiolabeling experiments demonstrated that P. carinii synthesizes sterols de novo. Cholesterol is the most abundant sterol in Pneumocystis; most, if not all, is scavenged from the mammalian host lung by the pathogen. The P. carinii erg7, erg6, and erg11 genes have been cloned, sequenced, and expressed in heterologous systems. The recombinant P. carinii S-adenosyl-L-methionine:C-24 sterol methyl transferase (SAM:SMT) has a preference for lanosterol over zymosterol as substrate, and the enzyme can catalyze the transfer of either one or two methyl groups to the C-24 position of the sterol side chain. Two different sterol compositions were detected among human-derived P. jirovecii; one was dominated by C28 and C29 sterols, and the other had high proportions of higher molecular mass components, notably the C32 sterol pneumocysterol. The latter phenotype apparently represents organisms blocked at 14alpha-demethylation of the sterol nucleus. These studies suggest that SAM:SMT is an attractive drug target for developing new chemotherapy for PcP.

Sterol biosynthesis in Pneumocystis: unique steps that define unique targets

Pneumocystis lacks ergosterol, and several antimycotics that bind ergosterol in fungal membranes or inhibit its synthesis are ineffective against Pneumocystis pneumonia. The organism synthesizes C(28) and C(29) Delta(7) 24-alkylsterols, 24-alkyllanosterol derivatives, and Delta(5) 24-alkylsterols, which may be produced by modifying scavenged Delta(5) sterols. Mammals cannot desaturate C-22 and alkylate C-24 of sterols, thus, these processes are particularly attractive targets for antifungal drug development. Recent data indicate that C-22 desaturation is not, but C-24 alkylation is an attractive target in P. carinii. The P. carinii S-adenosyl-L-methionine:sterol C-24 methyl transferase (SAM:SMT) has unique properties; it prefers lanosterol as its sterol substrate.