Tsenka Milkova

Sterols and volatiles in Cystoseira barbata and Cystoseira crinita from the black sea

Abstract Five sterols were identified in Cystoseira barbata and seven sterols in C. crinita . Saringasterol appeared to be an artefact. Volatiles in C. barbata consisted mainly of halogenated hydrocarbons, while in C. crinita terpenoids predominate. The results obtained can be used in chemosystematics.

4-Androsten-3,17-dione from cholesterol, β-sitosterol, and campesterol by chemical degradation

Abstract 1 was degraded to 24 in good overall yield via 7 , 10 , 16 , 21 , 19 and 20 ; similarly, 24 was obtained from 2 and 3 .

Sterol composition and biosynthesis in the Black Sea sponge Dysidea fragilis

Abstract The sterol composition of Dysidea fragilis from the Black Sea is reported. Three groups of sterols, Δ5, Δ0 and Δ5,7, were found. The isolated 5α,8α- epidioxy sterols appeared to be predominantly, if not exclusively, artifacts. The auto-oxidation of native Δ5,7- sterols to 5α,8α- epidioxy sterols has been investigated. A transformation of dietary Δ5- sterols to Δ5,7- sterols has been demonstrated in Dysidea fragilis.

Minor and trace sterols in marine invertebrates. 34 Isolation and structure elucidation of 24-methyl-5α-cholesta-7,9(11), 24(28)-trien-3β-ol, the first naturally occurring Δ7, 9(11) unsaturated marine sterol

Abstract The lipid fraction of a Black Sea sponge, Haliclona flavescens , was investigated for its sterol composition. Twenty-three sterols were identified, including the hitherto unknown 24-methyl-5α-cholesta-7, 9(11), 24(28)-trien-3β-ol ( 3 ). Identification and structure elucidation were based upon 360 MHz 1H-NMR and MS analyses.

Synthesis of potential ecdysteroid precursors from Δ7,22 sterols

Abstract Two routes for the conversion of 5α-cholest-7-ene-3β-ol (11) into 7, which has the typical ecdysteroid substitution pattern in rings B, C, and D, have been developed. Making use of one of the methods, 5,6-dihydroergosterol (31) was converted into the 38, possessing all the functionalities required for the synthesis of naturally occurring ecdysteroids.

Remote halogenation: Some model studies and specific degradation of the cholesterol, sitosterol, and campesterol side chain

Abstract 1) Two high-yield procedures for the conversion of 1 to 4 are reported. 2) 11 was degraded to 34 in good overall yield via 17, 20, 26, 31, 29, and 30. Similarly, 34 was obtained from 12 and 13.

14β-hydroxy steroids - VI. Synthesis of digitoxigenin

A short and efficient synthesis of digitoxigenin (10) is reported using a new method for the introduction of the 14β-OH group.

Isolation of 22-methylenecholesterol. Further evidence for direct bioalkylation of 22-dehydrocholesterol

Abstract The first isolation of a 22-monoalkylated analog of cholesterol, i.e., 22-methylene-cholesterol is reported and the biosynthetic implications of this observation discussed.

ANTIVIRAL ACTIVITY OF CHOLESTERYL ESTERS OF CINNAMIC ACID DERIVATIVES

Cholesteryl 3”,4”-dimethoxycinnamate (7) and a new synthesized o-coumaroyl ester of 3β- (2’-hydroxyethoxy)-cholest-5-en (13) exhibited a marked activity against poliovirus type 1 (Mahoney). Compound 7 showed an approximately 20-fold greater selectivity in its antiviral activity than compound 13. These compounds were selected from thirteen steryl esters of cinnamic acid derivatives through an in vitro antiviral screening against viruses belonging to taxonomic groups with causative agents of important human infectious diseases to which chemotherapy is indicated, i.e. Picornaviridae, Orthomyxoviridae, Paramyxoviridae and Herpesviridae.

Study on the antioxidant activity of cholesteryl esters of some phenolic acids by chemiluminescence

Abstract Four cholesteryl esters of cinnamic acid derivatives, cholesteryl 2″-hydroxycinnamate, cholesteryl 3″-hydroxycinnamate, cholesteryl 4″-hydroxy-cinnamate and cholesteryl 3″,4″-dihydroxycinnamate, as well as cholestanyl 2″-hydroxycinnamate, which can be used as potential inhibitors of lipids oxidation, have been investigated for their radical scavenging efficiency by a chemiluminescence method. The rate constants of inhibition( k 1nH ) were determined in a model reaction of an initiated oxidation of tetraline at 353 K. The chemiluminescent results show that the four cholesteryl esters are efficient radical acceptors, and that among them, cholesteryl 3″,4″-dihydroxycinnamate is a particularly efficient radical scavenger with an inhibition rate constant of 1.8 × 10 5 dm 3 mol 1 s −1 .