Digitonins

The third and fourth isomerides, viz., the two aZZosolanidanols, were prepared from solanidone (A Solatubenone of Roehelmeyer A -solaniden-3-one), already deseribed (p. 663), by hydrogenation with platinised Raney niekel in an alkaline medium. The reaetion produet yielded aZZosolanidan-3(a)-ol and aZZosolanidan-3(jS)-ol. R probably also ineluded the two solanidanols sinee the unerystallisable residue on epimerisation by sodium in boiling xylene followed by preeipitation with digitonin, yielded some solanidan - 3( j8 )-ol. 

Colour Reactions. Rochelmeyer (1939) has provided a list of colour reactions given by solasodine and solasodiene (solanosodine), with reagents usually applied to the sterols, and Briggs et al. have found that when concentrated sulphuric acid (1 mil) is carefully added to a solution of solasonine or solasodine in hot alcohol (1 mil) a characteristic, intense, greenish-yellow fluorescence is produced, a reaction which is not given by solanine or solanidine. They have also found that intense colours are formed when solasonine or solasodine is mixed with resorcinol, or one of a variety of aldehydes, and boiled with concentrated hydrochloric acid. Colours are also produced with this test by cholesterol, digitonin, jacobine carbazole, pyrrole, or nicotine, the most intense colours being formed with p-hydroxybenzaldehyde or anisaldehyde. 

Digitogenin, molecular formula and structure, 5 180t Digitonin, molecular formula and structure, 5 180t Digitoxin, 5 105, 184... 

Theory The assay of cholesterol is solely based on the fact that practically all 3 (3-hydroxysterols e.g., cholesterol, readily produces an insoluble molecular addition complex with pure digitonin (1 1)—a steroidal saponin isolated from either Digitalis purpurea or Digitalis lanata. The complex thus obtained is crystalline in nature, fairly stable and possesses very low solubilities. 

In many tissues cholesterol and other sterols exist as a mixture of the free alchohol and its long chain fatty acid ester (esterified at position 3 of the steroid nucleus). The determination of the cholesterol content of a sample may involve the measurement of either of these two fractions individually or the total cholesterol. It is possible to precipitate free cholesterol by adding an equal volume of digitonin (1 gl-1 in 95% ethanol), a naturally occurring glu-coside, to form a complex that is insoluble in most solvents, including water. 

The chemical methods for the quantitation of cholesterol measure total cholesterol, i.e. free and esterified, and so a digitonin precipitate must be prepared if free cholesterol is to be measured. Enzymic methods do not measure the esters and a hydrolysis stage, either chemical or enzymic (using cholesterol ester hydrolase, EC 3.1.1.13), is necessary for the measurement of total cholesterol. 

Between 1955 and 1960 various sub-mitochondrial preparations were developed to give vesicles comprising only sealed inner mitochondrial membranes. Cooper and Lehninger used digitonin extraction Lardy and Kielley Bronk prepared sub-mitochondrial particles by sonication. At this time, too, Racker and his colleagues isolated Fq/F1 particles from mitochondria and showed that a separated FI particle behaved as an ATPase. The F0 portion had no enzymic properties but conferred oligomycin sensitivity on the FI ATPase. The orientation of these sub-mitochondrial vesicles (inside-out or vice-versa) was shown by the position in electron micrographs of the dense (FI) particles which in normal intact mitochondria project into the matrix and so define the surface of the inner mitochondrial membrane. 

When micelles are used, the CE technique becomes a micellar elec-trokinetic chromatography (MEKC) one. Natural surfactants, such as bile salts, digitonin and saponins, optically active synthetic surfactants, e.g., amino-acid derived ones, alkylglycoside-, tartaric acid- and steroidal glucoside-based surfactants, and high-molecular mass or polymerized surfactants, have been used as chiral selectors in In the lat-... 

Fig. 4.3 CSF concentration/free (unbound) plasma concentration ratios for neutral and basic drugs 1, ritropirronium 2, atenolol 3, sulpiride 4, morphine 5, cimetidine 6, meto-prolol 7, atropine 8, tacrine 9, digoxin 10, propranolol 11, carbamazepine 12, ondansetron 13, diazepam 14, imipramine 15, digitonin 16, chlorpromazine and acidic drugs, a, salicylic acid b, ketoprofen c, oxyphenbutazone and d, indomethacin compared to log D.

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