168 SEEDS 



narrow endosperm. Moistened with 80 per cent, sulphuric acid the 

 section assumes, at least in the endosperm but sometimes in the coty- 

 ledons also, a deep emerald green colour. The same reaction is afforded 

 by the kernels from which the seed-coats have been removed after 

 soaking in water. The seed-coats thus separated, warmed on a slide 

 with a little saturated aqueous solution of choral hydrate and examined 

 under the microscope, are seen to contain not more than an occasional 

 crystal of calcium oxalate. The odour of the crushed seed is character- 

 istic, though not very powerful ; the taste is intensely bitter. 

 The student should observe 



(a) The colour of the seed and the satiny hairs, 



(b) The straight cotyledons and narrow endosperm, 



(c) The green reaction with sulphuric acid. 



Constituents. The active constituent of strophanthus seeds is 

 the glucoside strophanthin, of which they contain from 8 to 10 per 

 cent. This substance, which is the source of the green reaction with 

 sulphuric acid, is present in the endosperm, and frequently also in 

 the cotyledons. 



The seeds contain, in addition, about 30 per cent, of fixed oil, 

 together with kombic acid, strophanthic acid, choline, and trigonelline. 

 They yield about 4 per cent, of ash on incineration. 



Strophanthin, C 40 H 66 O 19 , forms colourless, intensely bitter, very 

 hygroscopic crystals freely soluble in water and*dilute alcohol, spar- 

 ingly soluble in absolute alcohol, and almost insoluble in ether or 

 chloroform. Warmed with a dilute mineral acid it is hydrolysed into 

 strophanthidin and a sugar (strophanthobiosemethylether). Stro- 

 phanthidin is also crystalline, but almost insoluble in water, and 

 separates in crystalline form when strophanthin is hydrolysed. 



It must, however, be observed that commercial strophanthin has 

 been shown to vary considerably in toxicity and that the strophanthins 

 prepared by different chemists from (as far as can be ascertained) 

 the same variety of seed, viz. $. Kombe, have shown differences in 

 the melting-point, in the hydrolysis, in the products yielded by the 

 hydrolysis, and in other respects, so that they appeared to be different 

 substances. It must, therefore, be admitted that the chemistry of 

 this body has not yet been sufficiently investigated. Brown and 

 Closson (1914) assert the presence of two strophanthins, a crystalline 

 and an amorphous. 



Strophanthic acid is an acid saponin (see p. 254). 



. The chemical methods that have been proposed for the assay of 

 strophanthus seed depend upon the extraction of the glucoside, and conversion 

 into strophanthidin which is weighed and from which the strophanthin present 

 is calculated. They are, however, all unsatisfactory. The drug may be 

 standardised by the bio-chemical method which consists in determining the 

 quantity of tincture which, after dilution with an equal volume of water, will 



