Rhubarb
Rhei Rhizoma
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Rhubarb is usually the rhizome of Rheum palmatum
Linneá , Rheum tanguticum Maximowicz, Rheum
officinale Baillon, Rheum coreanum Nakai or their
怎样做寿司interspecific hybrids (Polygonaceae).
It contains not less than 0.25z of nnosides A
(C42H38O20: 862.74), calculated on the basis of dried
material.
Description Ovoid, oblong-ovoid or cylindrical rhizome,
often cut crosswi or longitudinally, 4 . 10 cm in diameter,
5 . 15 cm in length. In the ca of Rhubarb without most
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part of cortex, the outer surface is flat and smooth, yellow-
brown to light brown in color, and sometimes exhibiting
white, fine reticulations; thick and hard in texture. In the
ca of Rhubarb with cork layer, externally dark brown or
reddish black, and with coar wrinkles; rough and brittle in
texture. The fractured surface of Rhubarb is not fibrous;
transver ction grayish brown, light grayish brown or
brown in color, having patterns of blackish brown tissue
complicated with white and light brown tissues; near the
cambium, the patterns often radiate, and in pith, consist of
whirls of tissues radiated from the center of a small brown
circle 1 . 3 mm in diameter and arranged in a ring or scat-
tered irregularly.
Odor, characteristic; taste, slightly astringent and bitter;
when chewed, gritty between the teeth, and coloring the
saliva yellow.
Under a microscope <5.01>, the transver ction reveals
mostly parenchyma cells; small abnormal cambium-rings
scattered here and there in the pith; the cambium-rings
produce phloem inside and xylem outside, accompanied with
2 to 4 rows of medullary rays containing brown-colored sub-
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stances, and the rays run radiately from the center of the
ring towards the outside forming whirls of tissues; paren-
chyma cells contain starch grains, brown-colored substances
or crystal drus of calcium oxalate.
Identification To 2 g of pulverized Rhubarb add 40 mL of
a mixture of tetrahydrofuran and water (7:3), shake for 30
minutes, and centrifuge. Transfer the supernatant liquid to a
parator, add 13 g of sodium chloride, and shake for 30
minutes. Separate the water layer with undissolved sodium
chloride, and adjust the pH to 1.5 by adding 1 mol/L hydro-
chloric acid TS. Transfer this solution to another parator,
add 30 mL of tetrahydrofuran, shake for 10 minutes, pa-
rate the tetrahydrofuran layer, and u this solution as the
sample solution. Separately, dissolve 1 mg of Sennoside A
RS in 4 mL of a mixture of tetrahydrofuran and water (7:3),
and u this solution as the standard solution. Perform the
test with the solutions as directed under Thin-layer Chro-
matography <2.03>. Spot 40 mL each of the sample solution
and standard solution on a plate of silica gel for thin-layer
国家专项计划chromatography at 10 mm along the initial line. Develop the
plate with a mixture of 1-propanol, ethyl acetate, water and
acetic acid (100) (40:40:30:1) to a distance of about 15 cm,
and air-dry the plate. Examine under ultraviolet light (main
wavelength: 365 nm): one of the spots from the sample solu-
tion and a red fluorescent spot from the standard solution
show the same color tone and the same Rf value.
Purity (1) 的字短语Heavy metals <1.07>.Proceed with 3.0 g of
pulverized Rhubarb according to Method 3, and perform the
test. Prepare the control solution with 3.0 mL of Standard
Lead Solution (not more than 10 ppm).
(2) Arnic <1.11>台词对白.Prepare the test solution with 0.40 g
of pulverized Rhubarb according to Method 4, and perform
the test (not more than 5 ppm).
(3) Raponticin.To 0.5 g of pulverized Rhubarb add ex-
actly 10 mL of ethanol (95), heat on a water bath with a
reflux condenr for 10 minutes, and filter. Perform the test
as directed under Thin-layer Chromatography <2.03>, using
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the filtrate as the sample solution. Spot 10 mL of the sample
solution on a plate of silica gel for thin-layer chromatogra-
phy <2.03>. Develop the plate with a mixture of isopropyl
ether, 1-butanol and methanol (26:7:7) to a distance of
about 10 cm, and air-dry the plate. Examine under ultravio-
let light (main wavelength 365 nm): no spot with blue-purple
fluorescence is obrved at an Rf value between 0.3 and 0.6,
though a bluish white fluorescence may appear.
Loss on drying <5.01> Not more than 13.0z (6 hours).
