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Corresponding author: Raghda Makia
Biotechnology College, Al-Nahrain University Baghadad, Iraq.
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Phytochemistry of the Genus Equisetum (Equisetum arvense)
Raghda Makia 1, *, Khulood W Al.sammarrae 2, Mohammad MF Al-Halbosiy 3 and Mohammed H Al-Mashhadani 4
1 Biotechnology College, Al-Nahrain University, Baghadad, Iraq.
2 Department of Forensic Techniques, Al-Farahidi University, Baghadad, Iraq.
3 Biotechnology Research Center, Al-Nahrain University, Baghadad, Iraq.
4 Department of Chemistry, College of Science, Al-Nahrain University, Baghdad, Iraq.
GSC Biological and Pharmaceutical Sciences, 2022, 18(02), 283–289
Publication history: Received on 01 January 2022; revised on 08 February 2022; accepted on 10 February 2022
Article DOI: https://doi.org/10.30574/gscbps.2022.18.2.0059
Abstract
The previous studies revealed that Equisetum arvense contained alkaloids, carbohydrate, proteins and amino acids,
phytosterols, saponins, sterols, ascorbic acid, silicic acid, phenol, tannin, flavonoids, triterpenoids, volatile oils and many
other biological active constituents. E. arvense has been used as a folklore medicine for treatment of various conditions
such as tuberculosis, as a catarrh in the kidney and bladder regions, as a hematostatic for profuse menstruation, nasal,
pulmonary, gastric hemorrhages and many other uses. The current review highlights the uses and phytochemical
constituents of E. arvense.
Keywords: Equisetum arvense; Alkaloids; Phytosterols; Hematostatic; Flavonoids
1. Introduction
Plants that possess therapeutic properties or exert beneficial pharmacological effects on the human body are generally
designated as medicinal plants. Medicinal plants naturally synthesize and accumulate some secondary metabolites like
alkaloids, sterols, terpenes, flavonoids, saponins and glycosides. The medicinal plants have been used for the treatment
of diseases and illness since the ancient times [1].
Iraq, like any other country of Middle East and elsewhere in the world, is differentiated into two societies: rural and
urban; both of these societies depend largely on the rich traditional heritage of the use of medicinal plants for the
treatment of different illnesses, hence folk medicine is widely practiced by the people of the cities and the inhabitants
of the remote areas or the nomads who generally inhabit the desert areas of the steppe and the uplands [2-3].
2. Family Equisetaceae
Equisetaceae, also sometimes named as horsetail family, is the only extinct family of the order Equisetales, with one
surviving genus, Equisetum, which comprises about twenty species. All available horsetails nowadays are belonging to
Eqisetum genus Equisetum. Also, some fossils are found that did not classify in the new classification system. Equisetites
is a "catch all taxon" unifying all different types of larger horsetails that belong to the Mesozic era [4].
3. Genus Equisetum
All Equisetum species are herbaceous perennials. The plants consist of upright aerial stems which arise from a very
extensive underground rhizome system [5]. Morphologically, the genus Equisetum is characterized by jointed aerial
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stems and jointed rhizomes. The stems of horsetails are anatomically unique among plants" [6] although they have an
external appearance somewhat reminiscent of bamboo. The upright aerial stems exhibit a monopodial branching
pattern, having one main axis of growth. Equisetum species also have small microphyllous leaves that are arranged in
true whorls [7] and the leaves of each whorl are fused together to form a cylindrical sheath around each node [8]. Some
but not all, species form whorls of lateral branches at the nodes of the aerial stems [9].
4. Equisetum arvense
Equisetum arvense commonly known as Horsetail is a bushy perennial herb, originally native to northern hemisphere
E. arvense belongs to Equisetaceae family in the order of Equisetales that contains just only one living genus [10]. The
genus Equisetum is divided into two subgenera Equisetum and Hippochaete based on some primary differences
concerning macromorphology and micromorphology, gametophyte morphology, chromosome size, and nuclear DNA C‐
values [11]. Horsetail is a strange-looking sort of plant with creeping, string like rootstock and roots at the nodes that
produce numerous hollow stems. Two markedly different types; the sterile stems tend to be much taller and bushier,
with the jointed segments being around one inch long with a diameter of about 1/20th of an inch. These segments
contain one set of whorled, slender, erect branches each. Some stems can have as many as 20 segments and be as tall as
2 to 24 inches. The fertile stems tend to be half as tall as the sterile stems and also tend to be more succulent. Fertile
stems unbranched, appear in early spring, usually thick and succulent, brownish to whitish, 10 to 30 cm tall. Sterile
stems bottlebrush-like (many whorls of slender branches), appear as fertile stalks wither 1-several in clusters, 10 to 50
cm tall; slender, green, 10 to 12 ridged, minutely roughened; branches simple, first branch segment longer than adjacent
stem sheath [10].
4.1. Distribution
Equisetum arvense was distributed throughout Europe and Asia, south to Turkey, Iran, Iraq the Himalayas, and across
China, Korea and Japan. It is also found throughout Canada and the USA [12-13].
Distribution of Equisetum arvense according to [14] is presented only in niberhood or the Ruwandiz district in the forest
zone of Iraq Khalan and between Khoran and Haji-Umran and close to Rubari Rusta. Its habitat according to [Townsend
1966] is ditches in orchard moist silt of perennial streams at flood level by road side on mountain slop at altitude 1100-
1500m during June-September. [14] suggested that very restricted distribution of this species iv Iraq may be due to its
restrictive to non-calcareous soil, lime free soil been very rear in our country but occurring in several localities to the
north east of Ruwandiz. Equisetum arvenus have a very wide range of distribution in Kurdistan. It has been recorded
from Gondazhour in Erbil district North West of Choman and also recorded far south of Kurdistan in Garmian area
specifically in Qula Sotaw [15].
4.2. Traditional uses
For a long time, E. arvense has been used as a folklore medicine for treatment of various conditions such as tuberculosis,
as a catarrh in the kidney and bladder regions, as a hematostatic for profuse menstruation, nasal, pulmonary and gastric
hemorrhages, for brittle fingernails and loss of hair, for rheumatic diseases, gout, poorly healing wounds and ulcers,
swelling and fractures and for frostbite. Horsetail can produce toxic effects on its prolonged use, especially when used
for long. Alkaloids although do not appear in strong concentrations, a prolonged use, can take place by accumulating
them in the organism which may facilitate premature childbirth, nervous disorders, headaches, loss of appetite,
swallowing problems, etc. These intoxications force to a treatment that restores the thiamine deficiency, although in the
case of the animals, they are no longer recoverable in many occasions [10].
4.3. Chemical constituents
The preliminary phytochemical analysis showed that the plant contained alkaloids, carbohydrate, proteins and amino
acids, phytosterols, saponins, sterols, ascorbic acid, silicic acid, phenol, flavonoids and triterpenoids [10-16-17-18]. The
plant contained silicic acid, tartaric acid, methyl esters of protocatechuic, caffeic acids isoquercitrin, apigenin and
kaempferol as phenolic compounds [17-19-20-21]. Stem contained silicic acid and silicates (5-8%), calcium (1.3%),
potassium (1.8%) and other minerals such as aluminium, sulphur, phosphorus, sodium, zinc, magnesium and
manganese [10-22-23-24]. Alkaloids such as nicotine, palustrine and palustrinine were isolated from the plant [25]. The
total phenolic content of n-butanol, ethyl acetate and water extracts were 96.4, 26.4 and 15.4 mg/g of dry extracts,
respectively [26]. The plant contained 0.6 to 0.9% flavonoids including apigenin glucoside, genkwanin glucoside,
kaempferol glucoside, kaempferol sophoroside, luteolin glucoside, quercetin glucoside. It was also contained caffeic acid
ester (up to 1% including chlorogenic acid, dicoffeoyl-meso-tartaric acid), 5-7.7% silicic acid and pyridine alkaloids, and
styrolpyrone glucosides [27-28-10-29]. The volatile constituents of the sterile stems of Equisetum arvense were
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investigated using GC, GC/MS and 13C-NMR. Twenty-five compounds were identified. Hexahydrofarnesyl acetone
(18.34%), cis-geranyl acetone (13.74%), thymol (12.09%) and trans-phytol (10.06%) were the major constituents [30].
4.4. Phytochemical active compounds of Equisetum arvense
Horsetail (Equisetum arvense L.) is well known as culinary and medicinal herb. Its fertile stems are consumed as food in
sweetened vinegar and in cooked food [31]. Horsetail was described as anti-inflammatory and antioxidant agent,
vasorelaxant, and was highly recommended by herbalists as haemostatic [32-33]. These activities of horsetail are
related to the content of several classes of secondary metabolites such as phenolics (flavonoids, styryl pyrones and
phenolic acids), alkaloids (equisetin, nicotine, palustrine and palustrinine), phytosterols (campesterol), bitter principle
and minerals (silica, calcium, magnesium, selenium, iron, potassium, zinc, etc.) [34-35-36-37]. The most widely known
phytochemical compounds of Equisetum arvense L. are flavonoids, phenolic acids, alkaloids, phytosterols, tannins and
triterpenoids [25].
5. Phytochemical constituents of Equisetum arvense
5.1. Flavonoids and their Glycosides
Flavonoids are an important class of natural products; particularly, they belong to a class of plant secondary metabolites
having a polyphenolic structure, widely found in fruits, vegetables and certain beverages. Flavonoids, a term usually
used to refer to a wide range of naturally occurring compounds that have (C6-C3-C6) base unit, or what is called phenyl
benzopyran structure [38]. Flavonoids can be subdivided into different subgroups depending on the carbon of the C
ring on which the B ring is attached and the degree of unsaturation and oxidation of the C ring (Figure 1). Flavonoids in
which the B ring is linked in position 3 of the C ring are called isoflavones. Those in which the B ring is linked in position
4 are called neo flavonoids, while those in which the B ring is linked in position 2 can be further subdivided into several
subgroups on the basis of the structural features of the C ring. These subgroups are: flavones, flavonols, flavanones,
flavanonols, flavanols or catechins, anthocyanins and chalcones as shown in figure (2).
Figure 1 Basic skeleton or structure of flavonoids
Flavonoids are biosynthesized from a phenyl propane-derived unit (C6- C3), the later source or origin is from shikimate
(from the amino acid phenylalanine) and an additional six carbons unit which is obtained from poly ketide biosynthetic
pathway. This poly ketide unit is synthesized from 3 units of malonyl-CoA, that are combined with the phenyl propane
derived unit (which is found as a CoA thioester) to generate the triketide molecule as a starter so that flavonoids are
biosynthesized by mixed pathways, including of fragments derived or obtained from both polyketide and shikimic acid
pathways [39].
All previous compounds are illustrated as the major constituents in the Equisetum arvense plant. Major constituent in
ethanolic extract of the plant is (quercetin3-O-glucoside) which is also known as (isoquercitrin), other glycosides are
available is considerable amounts such as kaempferol 3-O-glycoside and apigenin 5-O-glucoside [17]. Quercetin is
available in high concentrations, about 50 % of all total flavonoids in plant, but as the weather changes into summer
and becomes hotter, the quercetin amounts decrease rapidly [40]. The importance of the flavonoids is their health
benefit by acting as a free radicals scavenger converting them into much more ‘stable radical’ which in turn would
undergo reaction with another ‘flavonoid radical’ to yield two non-radicals [41].
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Figure 2 Flavonoid classes, subclasses and natural sources
5.2. Caffeic acid ester (about one percent)
These compounds are including chlorogenic acid, and dicoffeoyl-mesotartaric acid, their role in plant is thought to be a
protective agent against pests or microbes, while their pharmacological actions are antibacterial, and antiviral [42].
5.3. Silicic acid (about five percent)
It has role in regulating metabolism of different classes of secondary metabolites especially phenolic compounds, new
studies shows that silicon-treated plants produces significantly higher amounts of flavonoids than their intact
correspondent (43). Some European clinical studies reported that bone fractures heal significantly faster when
Equisetum arvense is used because of its high content of silica, also for the same reason it shows to decrease the incidence
of osteoporosis more greatly when Equisetum arvense is routinely used [10].
5.4. Alkaloids
The term Alkaloid is derived from the word alkaline; it previously was referred to any Nitrogen-containing compound.
They are biosynthesized by many beings, including bacteria, fungi, plants, and even animals. Many of them have a
pharmacological action and indicated to many therapeutic fields, such as caffeine, cocaine, nicotine, ephedrine and many
others [44]. It is difficult to find a specific definition for the term ‘alkaloid’ (alkalilike) due to that there is no clear-cut
border between alkaloid itself and other naturally occurring complex amines, the following is the most accepted
classification for alkaloids:
Typical alkaloids are defined as that extracted from plants, alkaline, and has at least a nitrogen atom ( usually
in a heterocyclic ring) in addition to that, usually they have a marked pharmacological use either on human or
on animals.
Proto-alkaloid: sometimes called ‘amino-alkaloid’ is a term occaisionally applied to refer to compounds such as
colchicine and ephedrine in which one or more of the features mentioned above of the typical alkaloids is
absent.
Other alkaloids: they aren’t fit with conventional or general alkaloids definitions, they are chemically
synthesized, not extracted from any natural source, at the same time they have a strong correlation to the
naturally occurring alkaloids (such as the anticholinergic agent homatropine) [45]. In Pharmacognosy practice,
these compounds are found in plants and gives positive results with the standard qualitative tests specified for
alkaloids, and frequently in plant researched these tests alone are used to identify a plant as ‘alkaloid-
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containing [46]. Alkaloids are reported to be present in E. arvense [48], are mainly from the Pyridine alkaloid
class, nicotine and palustrine are the main alkaloids reported to be present in Equisetum arvense [47].
5.5. Triterpinoids
Naturally occurring secondary metabolites, have a crucial role in regulation of plant interaction with its media or
environment, they may have a defense role to the plant, to prevent animals from feeding on the plant, or may have an
attractant role in the plant, and many of them have a pharmacological activity for animal and humans [49]. Among
phytochemicals that are reported to be found in Equisetum arvense that belong to this class, (Isobauerenol, taraxerol,
germanicol, ursolic acid, oleanolic acid, betulinic acid), Betulinic acid is pentacyclic compound with a well-known
anticancer activity [10].
6. Conclusion
The plant is reported to contain a number flavonoids, alkaloids, phenolic proteins, triterpenoids, saponins, phytosterols;
the present review is an attempt to generate interest among the masses regarding its immense potential in preventing
and treating several disorders.
Compliance with ethical standards
Acknowledgments
We would like to thank Al-Nahrain University for their support during this work.
Disclosure of conflict of interest
All authors of the manuscript have no conflict of interests to declare.
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