THE SAP0NINS

The saponins are plant products and belong to the group of compounds known as glycosides. Earlier they were known as " Glucosides"" as it was erroneously thought that they all contained glucose.

Glycosides as a class upon being heated with water or dilute acids show the characteristic property of under-going hydrolysis. They are also hydrolysed under the influence of enzymes when they are found to produce one or more molecules of a sugar or sugars or their oxidation products, uronic acids and an aglycone.

The detergent property of saponins and their plentiful supply from plants attracted attention at a very early stage. In the beginning their use was Y confined to washing and cleansing purposes. The barks and fruits of certain plants being generally used.

Later their use for washing fabrics, especially silk and woollen was found. With easy and ready availability of soap in quantities, their use in advanced countries went out of fashion, but was continued in less advanced parts of the world. They found preferential use over soap in the washing of delicate fabrics which are liable to be damaged by soap. It, therefore, seems, strange that for a long time such a useful and readily accessible plant material did not attract much attention of the chemist. It is only during the last twenty-five years or so that the attention has been focussed on their study.

The saponins are described as glycosides which produce copious foam when shaken with water, and possess certain marked physiological properties. The words of Bernard translated in English in this connection are worth quoting, " The saponins or the saponosides, as they are more correctly called, are heterosides, colloidal in nature and soluble in water. These substances are bitter, produce sneezing, haemolyse and give foam with water". Rosenthaler calls them glucosides (or corresponding uronic acid compounds) which foam copiously in water and whose aglucones belong to the group of polyterpenoids or that of cholanes.

The use of the word saponin seems to have been made for the first time in the first quarter of the 19th century. From the literature it appears that the word saponin may have been introduced by any one of the following three persons. Grothes (1815) is cited by Hichter as the person who introduced it while Wattiez and Stearnon credit it to Bochlez (1811). Sannie considers that it was Gmelin (1819) who used the word for the first time.

The word saponin is derived from the word "Sapo” meaning soap. There is definite evidence that in the early 19th century a number of compounds having such a property were obtained from the plant. Their hydrolysis as pointed out earlier results in the production of a sugar or sugars and one or more aglycones, called sapogenins. They help and stabilise the formation of emulsions.

C 0 N C L U S I 0 N S

The following conclusions may be drawn from the work described in the thesis.

1. The seeds of Albizzia procera, Benth., yields a glycaside-saponin, m.p. 156-58°.

2. The saponin on hydrolysis gave a sapogenin, m.p. 256-8° [a] D = + 82.4. This sapogenin is a triterpenic acid and belongs to the bamyrin-oleanolic acid group. The sapogenin has one double bond, one carboxyl and two hydroxyl groups.

3. The sapogenin yields a diacetate, m.p.258-60° [a] D = + 88, a methyl ester, m.p. 224-25° [a] D = + 80.7, a diacetylmethyl-ester, m.p.278-80° [a] D = + 90, diacetylbromo-lactone, m.p. 276-78° [a] D = +80, a ketolactone, m.p. 202-6° and an epoxide m.p. 95-110°.

4. The sapogenin could be identified as D12, 3b, 21 b-dihydroxy-18b-oleanene-28-oic acid or 21b-hydroxy-oleanolic acid (Machaerinic acid).

5. The acid hydrolysate of the saponin gives a mixture of sugars identified as d-glucose, d-xylose, d-arabinose and l-rhamnose.

6. The sugars are present in equimolecular proportions. A molecule of the genin appears to be combined with two moles each of glucose, xylose, arabinose and. Rhamnose.

7. The saponin so far as known to the author has been isolated for the first time and is named proceranin. 8. The seeds of Albizzia procera are the largest source of machaerinic acid so far known. The only other source, a certain species of cactus (Djerassi) gives it in traces only.

9. Machaerinic acid itself as such, has been isoiated for the first time. Some of its derivatives are also prepared.

10. The fatty acid composition of the seed-oil of Albizzia procera, Benth,» as determined by ester-fractionation method is as follows. Palmitic acid 7.23%, stearic acid 14.26%, arachidic acid 12.21% oleic acid 50.89% and linoleic acid 15.41%.

MOTS CLEFS : acid / aglucone / aglycone / albizzia / arabinose / cactus / cholane / compound / djerassi / glucose / glucoside / haemolyse / heteroside / ketolactone / linoleic / machaerinic / oil / oleic / palmitic / plant / procera / property / rhamnose / sapogenin / saponin / saponoside / seed / soap / sugar / uronic / xylose