A.3 Solanidine
Synonym Solatubine.
Biological Source The plant of Capsicum annuum L. (Solanaceae) (Chili, Peppers, Paprika) contains solanidine.
Chemical Structure
(3b)-Solanid-5 en-3-ol; (C27H43NO).
Isolation It is obtained by the hydrolysis of solanine which yields one mole each of L-Rhamnose, D-Galactose, and D-Glucose as shown below.
Characteristic Features
1. The long needles obtained from chloroform-methanol have a mp 218-219°C. It usually sublimes very close to its mp with slight decomposition.
2. It is specific rotation [α ]D21 -29o (c = 0.5 in CHCl3).
3. It is freely soluble in benzene, chloroform, slightly in methanol and ethanol; and almost insoluble in ether and water.
Identification Tests The same as described under A.1. earlier in this section. Besides, it has the following specific features for the corresponding derivatives, namely:
(a) Hydrochloride Derivative: (C27H43NO.HCl): Prisms from 80% alcohol and gets decomposed at 345°C.
(b) Methyliodide Derivative: (C27H43NO.CH3I): Crystals from 50% (v/v) ethanol and decomposes at 286°C.
(c) Acetylsolanidine Derivative: (C29H45NO2): Crystals obtained from ethanol having mp 208°C.
Biosynthesis of Solasodine, Tomatidine and Solanidine Like the sapogenins, the steroidal alkaloids are also derived from cholesterol, with suitable side-chain modification during the course of biochemical sequence of reactions as given under.
From the above biochemical sequence of reactions it is evident that:
(i) L-arginine seems to be used as a source for N-atom through amination via a substitution process upon 26-hydroxycholesterol,
(ii) Another substitution affords 26-amino-22-hydroxycholesterol to cyclize thereby forming a heterocyclic piperidine ring,
(iii) After 16β-hydroxylation, the secondary amine is oxidized to an imine, and the ultimate spirosystem may be envisaged by virtue of a nucleophilic addition of the 16β-hydroxyl on to the imine, and
(iv) This specific reaction, however, establishes the configurations, viz: 22R-as in the case of Solasodine, and 22S-as in the case of Tomatidine.
B. Veratrum Alkaloids The Veratrum alkaloids represent the most important and medicinally significant class of steroidal alkaloids. It is, however, pertinent to mention here that the basic ring systems present in the Veratrum alkaloids are not quite the same as seen in the usual steroidal nucleus, as present either in the cholesterol or in the aglycone residues of the cardiac glycosides
(A). Interestingly, one may observe in the structures of Veratrum alkaloids that the ring ‘C’ is a fivemembered ring while ring ‘D’ is a six-membered ring (B) which apparently is just the reverse of the pattern in the regular steroidal nucleus as depicted in next page.
Examples
(a) Alkamine portion of the ester alkaloids of Veratrum, viz., Protoverine, Veracevine, Germine.
(b) Alkamine aglycones of glycosidic veratrum alkaloids, viz., Veratramine.
In general, the majority of Veratrum alkaloids may be classified into two categories solely based on their characteristic structural features, namely:
(i) Cevaratrum alkaloids, and
(ii) Jeveratrum alkaloids
These two categories of Veratrum alkaloids shall now be discussed individually in the sections that follows:
