RADIX HEMIDESMI.
Hemidesmus Root, Nunnari Root, Indian Sarsaparilla.
Botanical Origin—Hemidesmus indicus R. Brown (Periploca indica Willd., Asclepias Pseudo-sarsa Roxb.), a twining shrub, growing throughout the Indian Peninsula and in Ceylon. The leaves are very diverse, being narrow and lanceolate in the lower part of the plant, and broadly ovate in the upper branches.[1564]
History—In the ancient Sanskrit literature the plant occurs frequently under the name Sārivā, and its root under the name of Nannārī or Ananta-mūl (i.e. endless root) has long been employed in medicine in the southern parts of India.[1565] Ashburner in 1831 was the first to call the attention of the profession in Europe to its medicinal value.[1566] In 1864 it was admitted to a place in the British Pharmacopœia, but its efficiency is by no means generally acknowledged.
Description[1567]—The root is in pieces of 6 inches or more in length; it is cylindrical, tortuous, longitudinally furrowed, from ²/₁₀ to ⁷/₁₀ of an inch in thickness, mostly simple or provided with a few thin rootlets emitting slender, branching woody aerial stems, ³/₀ of an inch or less thick. Externally it is dark brown, sometimes with a slight violet-grey hue, which is particularly obvious in the sunshine. The transverse section of the hard root shows a white mealy or brownish or somewhat violet cortical layer, not exceeding ⅒ of an inch in thickness, and a yellowish woody column, separated by a narrow dark undulated cambial line. Neither the wood nor the cortical tissue present a radiate structure in the stout pieces; in the thinner roots, medullary rays are obvious in the woody part. The extremely thin corky layer easily separates from the bark, which latter is frequently marked transversely by large cracks. The root, whether fresh or dried, has an agreeable odour resembling tonka bean or melilot. The dried root has a sweetish taste with a very slight acidity. The stems are almost tasteless and inodorous. The root found in the English market is often of very bad quality.
Microscopic Structure—All the proper cortical tissue shows a uniform parenchyme, not distinctly separated into liber, medullary rays and mesophlœum. On making a longitudinal section however, one can observe some elongated laticiferous vessels filled with the colourless concrete milky juice. In a transverse section, they are seen to be irregularly scattered through the bark, chiefly in its inner layers, yet even here in not very considerable number. They are frequently 30 mkm. in diameter and not branched.
The wood is traversed by small medullary rays, which are obvious only in the longitudinal section. The parenchymatous tissue of the root is loaded with large, ovoid starch granules. Tannic matters do not occur to any considerable amount, except in the outermost suberous layer.
Chemical Composition—The root has not been submitted to any adequate chemical examination. Its taste and smell appear not to depend on the presence of essential oil, so far as may be inferred from microscopic examination; and it is probable the aroma is due to a body of the cumarin class. According to Scott,[1568] the root yields by simple distillation with water a stearoptene, which is probably the substance obtained by Garden in 1837, and supposed to be a volatile acid.
Uses—The drug is reputed to be alterative, tonic, diuretic and diaphoretic, but is rarely employed, at least in England.