RHUBARB 369 



ponticin ; not an anthraquinone derivative) , the presence of which can 

 be demonstrated by the following test : 



Percolate 10 gm. of the powdered drug with 60 per cent, alcohol ; col- 

 lect 25 c.c. of the percolate, evaporate at 80 to 7 gm., shake vigorously 

 while still warm with 10 c.c. of ether, pour off the ethereal solution into 

 a small flask, cork and set aside ; needle-shaped crystals of rhaponticin 

 will separate within 24 hours. This test serves to identify the drug 

 derived from R. rhaponticum, and will detect it in a mixture of 1 part 

 of rhapontic rhubarb with 3 of Chinese but in this case crystals do not 

 separate for a few days. 



Rhapontic rhubarb also contains chrysophanic acid, a crystalline 

 substance chrysopontin, C 16 H 16 O 5 , and a glucoside yielding by hydro- 

 lysis chrysorhapontin, C 16 H 16 4 . According to Hesse the drug contains, 

 in addition to rhaponticin and chrysophanic acid, anhydrorhapontigenin, 

 rhabarberone, chrysarone, gluco-chrysarone, gallic acid and rhapontic 

 acid. 



Chinese Rhapontic Rhubarb. This variety has latterly been imported 

 from China ; it closely resembles English rhapontic but is usually darker, 

 often hollow in the centre, the section exhibiting alternating paler and 

 darker concentric rings and a yellow rather than pink colour ; it 

 yields rhaponticin by the test described above. 



Allied Drugs. Many species of Rumex contain oxymethylanthra- 

 quinone derivatives and have been used as substitutes for rhubarb, 

 e.g., R. alpinus, Linne, R. obtusifolius, Linne, &c. 



R. hymenosepalus, Torrens, yields canaigre root, used in America 

 for tanning (30 per cent, of tannin). 



KAVA RHIZOME 



(Kava-kava: Kavae Rhizoma) 



Source, &c. Kava rhizome is the rhizome of Piper metJiysticum 

 Forster (N.O. Piperacece), a shrub indigenous to the Sandwich Islands. 

 The plant produces a large rhizome which should be freed from roots 

 and periderm, cut into pieces and dried. 



Description. Although the British Pharmacopoeia requires that 

 thejperiderm should be removed, much of the^commercial drug is 

 unpeeled. The larger rhizomes are cut into irregularly cubical or 

 wedge-shaped pieces or slices about 1 to 5 cm. thick ; the smaller 

 may be entire and have numerous stout roots attached, the drug 

 then exhibits a dark grey periderm within which is a whitish or pale 

 brownish grey cortex and a narrow ring of whitish wood enclosing a 

 large, dense, often discoid pith of the same colour. In the wood 

 slender vascular bundles with distinct vessels alternate with wide 

 medullary rays. This structure is best seen in the smaller rhizomes. 



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