76 CARBOHYDRATES [ch. 



tissues are macerated and extracted with water to whicli chloroform 

 has been added, the cells die more rapidly and yield up the enzyme to 

 the solvent. From such a water extract, a crude precipitate containing 

 the enzyme may be obtained by addition of alcohol. For obtaining the 

 maximum results with diastatic activity in leaves, a water extract should 

 be made after they have been killed, either by drying, or by the action 

 of toluol or chloroform. 



It has been shown (Brown and Morris, 6) that in leaves which con- 

 tain tannin, the presence of the latter largely inhibits the action of the 

 enzyme and may be the cause, in such cases, of an entire lack of activity 

 in the extract. 



The diastatic activity of leaves appears to vary largely in different 

 genera and species. The subject has been investigated (Brown and 

 Morris, 6) and a list of their relative activities has been drawn up as 

 follows. 



[The numbers represent the amount of maltose, expressed in grams, which 10 

 gms. of air-dried leaf will produce from soluble-starch (starch treated with dilute 

 hydrochloric acid) by hydrolysis in 48 hrs. at 30° C] 



Pisum sativum 240*30 Helianthus annuus 3-94 



Phaseolus multiflorus 110'49 H. tuberosus 378 



Lathyrus odoratus 100*37 Funkia sinensis 5*91 



L. pratensis 34*79 Allium Cepa 3*76 



Trifolium pratense 89*66 Hemerocallis fulva 2*07 



T. ochroleucum 56*21 Populus sp 3*79 



Vicia sativa 79*55 Syringa vulgaris 2*53 



V. hirsuta 53*23 Cotyledon Umbilicus 4*61 



Lotus corniculatus 19*48 Humulus Lupulus 2*01-9*60 



Lupinus sp 3*51 Hymenophyllum demissum ... 4*20 



with Clover 27*92 Hydrocharis Morsus-ranae ... 0*267 



Tropaeolum majus 3*68-9*64 



From the above table it is seen that the leaves of genera of the 

 Leguminosae are apparently very rich in diastase. Whether this is so, 

 or whether in other plants the diastatic activity is inhibited by other 

 substances, has not yet been ascertained. As mentioned above, tannins 

 inhibit the action of diastase, and hence leaves rich in tannin, e.g. Hop 

 {Hamulus), cannot be expected to yield good results. 



The tissues of germinating barley (Hordeum vulgare) also contain 

 large quantities of diastase, and this material can be used to demonstrate 

 the solubility, isolation and activity of the enzyme. 



The action on starch of diastase from the leaf of the Common Pea 

 (Pisum sativum) and from germinating barley grains has already been 



