White front
1、 Pharmacopoeia standard of Baiqian       This product is the dried rhizomes and roots of the Asclepiadaceae plant Cynanchum Stauntonii (decne.) schltr.ex levi. or Cynanchum glaucescens (decne.) hand.-mazz. Excavate in autumn, wash and dry.
      [character] the rhizome of Salix alba is slender cylindrical, branched, slightly curved, 4-15cm long, 1.5-4MM in diameter. The surface is yellowish white or yellowish brown, with obvious nodes, 1.5-4.5cm long internodes, and residual stems at the top. It is brittle and hollow in cross section. At the node, there are clusters of slender curved roots, up to 10cm in length, less than 1mm in diameter, with many branches in the shape of hair whiskers, which are often coiled into clusters. It tastes slightly sweet.
      The rhizome of Daphne genkwa is short or slightly massive; The surface is grayish green or grayish yellow, and the internode is 1 ~ 2cm long. The texture is relatively hard. The root is slightly curved, about 1mm in diameter, and has few branches.
      [identification] take 1g of crude powder of this product, add 10ml of 70% ethanol, heat and reflux for 1 hour, and filter. Take 1ml of filtrate, evaporate it to dryness, add 1ml of acetic anhydride to dissolve the residue, and add 1 drop of sulfuric acid. The willow leaves turn red purple before they are white, and turn dirty green after being placed; The leaves of Daphne genkwa are brownish red before they are white and do not change color after placing.
      Decoction pieces
      [processing] Baiqian   Remove impurities, wash, moisten, segment and dry.
      Honey white front   Before taking the pure white, stir fry according to the honey roasting method (general rule 0213) until it is not sticky.
      [nature, taste and meridian tropism] pungent, bitter and mild. Return to lung meridian.
      [functions and indications] reduce Qi, eliminate phlegm, and stop cough. For lung qi congestion, cough and phlegm, chest full of asthma.
      [usage and dosage] 3 ～ 10g.
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2、 Chemical constituents of plantain
The rhizome of Salix Alba containsβ - sitosterol（β-sitosterol）， Higher fatty acids and hancokind [1]2. the roots of Daphne genkwa leaves contain glaucosides a, B, C, D, e[2], F, g[3], h, I, j[4], k[5], glaucogenin A and B, glaucogenin c-mono-d-thevetlside [6], neoglaucoside A and b[5], and glaucogenin C aucobiose) [7].

3、 Pharmacological action of Rhizoma Plantaginis
Saponins have expectorant effect