Rhizoma Dioscoreae Oppositae
（山药，Shanyao）
Common Yanm Rhizome
Common Yanm Rhizome is the dried rhizome of Dioscorea opposita Thunb. (Fam.
Dioscoreaceae). The drug is collected in winter when the stem and leaves are withered,
cut off, washed clean and peeled outer bark and fibrous roots, and then dried.
Alternatively, the large, straight and dried rhizome is sorted, soaked in clean water
until no dry core visible and softened thoroughly, cut two ends to smooth plane and
rubbed on a board to become cylindrical in shape, dried in the sun, finally polished. It
is known as “Guang Shanyao”(Polished Common Yanm Rhizome).
Description Subcylindrical, curved or somewhat flattened, 15-30cm long, 1.5-6cm
in diameter. Externally yellowish-white or pale yellow, longitudinally furrowed and
wrinkled, and bearing fibrous root scars, with occasional patches of brownish cork.
Texture heavy, compact and tough; uneasily broken, fracture white and starchy. Odour,
slight; taste, weak, acidulous, and viscous on chewing. Guang Shanyao is cylindrical,
the two ends even, 9-18cm long, 1.5-3cm diameter, externally smooth, white or
yellowish-white.
Identification (1)Powder: Whiteish. Simple starch granules compressed-ovoid,
deltoid-ovoid, subrounded or oblong, 8-35μｍ in diameter, hilum pointed, V-shaped,
crosscriss or shortly cleft, striations visible. Compound starch granules few, usually
consisting of 2-3 granules. Mucilage cells containing raphides of calcium oxalate, up
to 240μｍ long and needle crystals 2-5μｍ wide. Vessels bordered-pitted, reticulated,
spiral and annular, 12-48μｍ in diameter.
(2)Heat under reflux 5g of the powder in 30ml of dichloromethane for 2
hours, filter, evaporate the filtrate to dryness, dissolve the residue in 1ml of
dichloromethane as the test solution. Heat under reflux 5g of the dioscin in 30ml of
dichloromethane for 2 hours, filter, evaporate the filtrate to dryness, dissolve the
residue in 1ml of dichloromethane as the reference solution. Carry out the method for
thin layer chromatography(Appendix VI B), using silica gel G as the coating
substance and mixture of acetidin, methanol and srong ammonia solution (9:1:0.5) as
the mobile phase. Apply separately to the plate 4μl of each of the above two solutions.
After developing and removal of the plate, dry in air. Spray with 10% solution
phosphomolybdic acid in ethanol, and heat to the spots clear. The spot in the
chromatogram obtained with the test solution correspond in position colour to the spot
in the chromatogram obtained with the reference solution.
Checking Water content Not more than 16.0% (Appendix IX H,method 1)
Total ash Not more than 4.0%(Appendix IX K)
Extractives Carry out the method for determination of water soluble
extractive(Appendix X A, the merceration), not less than 7.0%.