Liebermann Burchard reaction

Liebermann-Burchard reaction diazo derivatives nitrated derivative... 

In an attempt to identify the chromophoric systems resulting from reactions of steroids with strong acids ( colour reactions Kober, Allen, Oertel, Talbot, Salkowski, and Liebermann-Burchard reactions) a detailed study has been made, with use of all the usual spectroscopic techniques. Visible colours are attributed generally to charge-transfer between the steroid, as donor, and a delocalized carbonium ion, generated from the steroid in acidic media, acting as acceptor. The structures of the steroidal carbonium ions are discussed. 

Another modified Pearson technique was published in 1963 and 1964 by Kenny and Jamieson (Jl, K2, K3). The procedure differs from that of Boy in respect to composition and volume of reagents, as well as temperature and time for the reaction to take place. Kenny uses a reaction temperature of 45°C, but employs a greater time for color development. Kenny et al. found differences between the automated results and those obtained by an extraction procedure (Kl) utilizing the Liebermann-Burchard reaction. They feel that the differences result from the presence of water in serum causing a decrease in absorbance, which is not encountered in the water-free acetic acid-cholesterol standard solution. Therefore, these authors have adjusted the cholesterol standards to compensate for the color depression, thus allowing direct reading of results. 

Another automated direct cholesterol technique for sera utilizes a modified Liebermann-Burchard reaction, employing a moderately stable reagent consisting of acetic acid-acetic anhydride and concentrated... 

A part of the specimen N-93 was extracted with chloroform, and a glycoside fi action (S-chf) was obtained. The residue was extracted with methanol. For the reference, the chloroform extracts of the roots of C. caudatum and C. wilfordii were prepared and named A-chf and B-chf, respectively. All the chloroform extracts, S-chf, A-chf and B-chf, gave positive Keller-Kiliani reaction and Liebermann-Burchard reaction, showing the presence of 2,6-dideoxysugar and steroidal skeleton in their structures, respectively. However, the HPTLC pattern of S-chf on a silica gel plate developed by CHCl3-Me0H-H20 (65 35 10, lower layer) was different fi om those of A-chf and B-chf (Fig. 1)... 

All compounds were positive in the Liebermann-Burchard reaction and showed the strong hydroxyl and ester absorption in the infrared(IR) spectra. They were all deduced to be triterpenoid saponins by analyzing the data of NMR and MS spectra. 

Cholesterol occurs in most biological materials in both the free and esterified forms. Quantitative determination of cholesterol is based on color reactions, which are not absolutely specific but suffice since cholesterol is the predominating sterol in most materials. The color reactions include the Liebermann-Burchard reaction with sulfuric acid and acetic acid anhydride, the Tschugaeff reaction with zinc chloride and acetyl chloride in acetic acid, or the Lifschiitz reaction with ferric chloride in acetic acid and sulfuric acid. Both free and esterified cholesterol participate in these reactions. Methods for the determination of cholesterol which are commonly used are those of Schoenheimer and Sperry (1934), Sperry and Webb (1950), Zak et al. (1951), Zlatkis et al. (1953). They were recently reviewed by Vanzetti (1964). 

For the quantitative determination of Solarium alkaloids in plant materials some new methods have been developed for instance, gravimetric procedures using the afore-mentioned cholesterol precipitation (15) for tetraosides, especially with saturated aglycones volumetric methods with titration of the bases in water-free solvents using aromatic sulfonic acids (26c, 47, 48) a number of simplified spectrophotometric methods by applying the Clarke reaction (49), that is, the hlue color obtained with paraformaldehyde-phosphoric acid in the case of J -unsaturated steroid alkamines and their glycosides (12, 50-52a, 525), or with the aid of amphi-indicators of the tropaeolin type (52,53-57,57a). The well-known Liebermann-Burchard reaction is not applicable to nitrogenous 3 -hydroxy-J -steroids (55). ... 

Considerable use of a number of its chemical and physical properties has been made in the isolation and quantitative determination of cholesterol. Cholesterol forms a very stable and quite insoluble molecular compound with the saponin, digitonin. The majority of sterols with hydroxyl groups at Cs in the 3 orientation likewise form more or less sparingly soluble digitonides. When treated with strong mineral acid, cholesterol forms a variety of colored complexes useful for the qualitative and quantitative determination of the compound. The most widely recognized of these is the Liebermann-Burchard reaction, in which the sterol Windaus, A., Ber. deut. diem. Oee. 42, 238 (1909). 

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