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Herba Equiseti
0.5% mineral matter (2). Thin-layer chromatography for determining the
absence of other Equisetum species and hybrids (1, 30). Chemical, sulfated
ash and alcohol-soluble extractive limits to be established in accordance
with national requirements.
Chemical assays
Contains not less than 0.3% of total flavonoids expressed as isoquercitroside
(isoquercitrin) (1).
Major chemical constituents
Asian and North American varieties contain a large amount of quercetin
3-O-β-d-glucopyranoside (isoquercitrin) and its malonyl esters. Apigeninand
luteolin 5-O-glucosides, as well as their malonyl esters are also present.
In the European chemotype, the flavonoids are mainly quercetin 3-Osophoroside
together with genkwanin and kaempferol derivatives, among
them protogenkwanin 4´-O-β-d-glucopyranoside (23, 35), genkwanin-5-
O-glucoside, kaempferol 3,7-di-O-glucoside, kaempferol-3-O-(6´-Omalonyl-glucoside)-7-O-glucoside,
kaempferol-3-O-sophoroside and glycosides
of luteolin (among them the 5-glucopyranoside, galuteolin), onitin
and onitin-9-O-glucoside (4, 36, 37). The plant also contains more than
10% inorganic constituents of which two thirds are silicates (which can
constitute as much as 15% (17)) and potassium salts (5). Small amounts of
gold (0.03–0.075 ppm) and silver (0.23 ppm) and lanthanides have been reported
(38) as well as traces of alkaloids, including nicotine and spermidine-type
bases, and palustrine. The sterols β-sitosterol, campesterol, isofucosterol
and cholesterol are present (37). Other constituents reported
include methoxypyridine, equisetonin, equisetroside, sapogenin and equisetogenin
(7, 8). In addition, there are saponins, carotenoids, polyenic acids,
rare dicarboxylic acids (5) and organic acids (aconitic, arabinonic, caffeic,
citric, equisetolic, fumaric, gallic, gluconic, glyceric, malic, malonic,
protocatechuic and quinic), and rhodoxanthin, threonic, p-coumaric, 4-hydroxybenzoic
and vanillic acid among others (7, 8, 37, 39). The structures
of some characteristic constituents are presented below.
CO 2
H
CO 2
H
palustrine
H
N
O
H
N
equisetolic acid
H 3
C
H
H
OH
H
N
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