28 LEAVES 



Not unfrequently the small flowers with five whitish petals and the 

 brownish fruits with five carpels may be found in the drug. 



The leaves have a characteristic odour recalling peppermint, and 

 a strong aromatic taste. 



The student should carefully observe 



(a) The rhomboidal outline and recurved apex, 



(b) The oil-glands and their distribution, 



(c) The characteristic odour and taste ; 



and should compare the official variety with the other commercial 

 buchu leaves mentioned below, as well as with 



Bearberry leaves, which are rounded at the apex, spathulate 

 in outline, and destitute of oil-glands. 



Constituents. The principal constituents of buchu leaves are 

 volatile oil and mucilage, the former being contained hi the oil-glands, 



Mill 



FIG. 17. Buchu leaves (B. serratifolia). Natural size. 



whilst the latter is deposited on the inner walls of the epidermal 

 cells. They contain in addition a yellow crystalline substance, 

 hesperidin, which is found in several other Kutaceous plants, but 

 does not markedly contribute to the physiological action of the drug ; 

 this substance forms sphere-crystals in the epidermal cells. The 

 volatile oil (1 '3 to 2 per cent.) deposits about 30 per cent, of crystalline 

 diosphenol, C 10 H 16 O 2 , when it is cooled. Diosphenol has antiseptic 

 properties, and is considered by some to be the most important 

 constituent of buchu ; its absence from the variety known as long 

 buchu has led to the exclusion of the latter from the British Pharma- 

 copoeia. The oil also contains a ketone, probably identical with 

 menthone, to which the peppermint-like odour is due. 



Diosmin, which has been reported as a constituent of buchu, is 

 probably impure hesperidin. 



Varieties. Barosma serratifolia, Willdenow. The leaves of this 

 plant, which, like B. betulina, is also a native of South Africa, are 

 imported in considerable quantity, and known commercially as ' long 

 buchu.' They are about 2'5 to 4 cm. long and linear-lanceolate in 

 outline. The margin is serrate, and the apex distinctly truncate. 



