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What
is Aloe vera?
Aloe
vera is a perennial, drought-resisting, succulent plant belonging to
the Lily (Liliaceae) family which, historically, has been used for a
variety of medicinal purposes. The plant has stiff grey-green
lance-shaped leaves containing clear gel in a central mucilaginous
pulp. Clinical evaluations have revealed that the pharmacological
active ingredients are concentrated in both the gel and rind of the
aloe vera leaves. These active ingredients have been shown to have
analgesic and antiinflammatory effects.
The true aloe vera
plant is called Aloe barbadensis Miller, otherwise called the
Curacao aloe, and is the most medicinally potent of the 300 (and
more) varieties found around the world. Most people in the UK today
know of aloe vera because of its inclusion in many popular cosmetic
products. Over the years, the plant has been known by a number of
names such as ‘the wand of heaven’, ‘heaven’s blessing’
and ‘the silent healer’. Although not medically recognised as a
therapeutic preparation, there have been many reports of the healing
power of aloe vera and, in recent years, clinical studies have been
undertaken.
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The
healing properties of Aloe Vera
The healing
properties of the succulent plant aloe vera have been known for
thousands of years. Belonging to the lily family and related to the
onion, garlic and asparagus, evidence supporting the early use of
aloe was discovered on a Mesopotamian clay tablet dating from 2100
BC. In Cairo in 1862, George Ebers, a German Egyptologist, bought a
papyrus which had been found in a sarcophagus excavated near Thebes
a few years earlier. Aloe vera as a herbal preparation, was
mentioned in the papyrus no fewer than 12 times.
Aloe vera was well
known not only to the Egyptians, but also the Roman, Greek, Arab and
Indian cultures. In fact, many famous physicians of those times,
including Dioscorides, Pliny the EIder and Galen - considered to be
the father of modem medicine - included aloe vera in their
therapeutic armouries.
Myths and legends
surrounding the use of aloe vera in ancient times suggest that it
was an important part of the beauty regime of the Egyptian queens,
Nefertiti and Cleopatra. Legend has it that, in 333 BC, Alexander
the Great was persuaded by his mentor Aristotle to capture the
island of Socotra in the Indian Ocean, famed for its supply of aloe
which he needed to heal his wounded soldiers.
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Recent
research
Some
recent studies appear to show topical and orally administered aloe
vera preparations in patients with chronic venous leg ulcers may aid
healing.
The research was
undertaken in three parts:
-
A literature
review of the composition and actions of aloe vera
-
Laboratory work
with cell cultures
-
A pilot study
using aloe vera for the treatment of chronic venous leg
ulcers.
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The
physical and chemical properties of Aloe Vera
The aloe
plant, being a cactus plant, is between 99 and 99.5 per cent water,
with an average pH of 4.5. The remaining solid material contains
over 75 different ingredients including vitamins, minerals, enzymes,
sugars, anthraquinones or phenolic compounds, lignin, saponins,
sterols, amino acids and salicylic acid. These are described in more
detail below.
Vitamins
The plant contains many vitamins, excluding vitamin D but including
the important antioxidant vitamins A, C and F. Vitamins B
(thiamine), niacin, vitamin B2 (riboflavin), choline and
folic acid are also present. Some authorities suggest that there is
also a trace of vitamin B12 (Coats1979).
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Enzymes
When taken
orally, several of these biochemical catalysts, such as amylase and
lipase, can aid digestion by breaking down fats and sugars. One
important enzyme, a carboxy-peptidase, inactivates bradykinins and
produces an anti-inflammatory effect. During the inflamma-tory
process, bradykinin produces pain associated with vasodilation and,
therefore, its hydrolysis reduces these two components and produces
an analgesic effect (Obata et al 1993, Shelton 1991).
Minerals
Sodium,
potassium, calcium, magnesium, manganese, copper, zinc, chromium and
iron are all found in the aloe plant. Magnesium lactate inhibits
histidine decarboxylase and prevents the formation of histamine from
the amino acid, histadine (Shelton 1991). Histamine is released in
many allergic reactions and causes intense itching and pain. The
prevention of its formation may explain the antipuritic effect of
aloe vera.
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Sugars
Sugars are
derived from the mucilage layer of the plant under the rind,
surrounding the inner parenchyma or gel. They form 25 per cent of
the solid fraction and comprise both mono- and polysaccharides. By
far the most important are the long chain polysaccharides,
comprising glucose and mannose, known as the gluco-mannans (Beta -
(1, 4) - linked acetylated mannan). When taken orally, some of these
bind to receptor sites that line the gut and form a barrier,
possibly helping to prevent ‘leaky gut syndrome’. Others are
ingested whole by a method of cellular absorption known as
pinocytosis. Unlike other sugars which are broken down prior to
absorption, the polysaccharides are absorbed complete and appear in
the blood stream unchanged. Here, they act as immuno-modulators —
capable of enhancing and retarding the immune response (Green 1996,
Kahlon etal 1991, Sheets etall9gi).
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Anthraquinones
These
phenolic compounds are found in the sap. The bitter aloes consist of
free anthraquinones and their derivatives:
In large amounts
these compounds exert a powerful purgative effect, but when smaller
they appear to aid absorption from the gut, are potent antimicrobial
agents (Lorenzetti et all 964, Sims eta/i 971 a), and
possess powerful analgesic effects. Topically, they can absorb ultra
violet light, inhibit tyronase activity, reduce the formation of
melanin and any tendency to hyper-pigmentation (McKeown 1987,
Strickland eta/i 993). Lignin This woody substance, inert in
itself, endows topical aloe preparations with their singular
penetrative ability to carry other active ingredients deep into the
skin to nourish the dermis (Coats 1979).
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Saponins
These
soapy substances form 3 per cent of the gel and are general
cleansers, having antiseptic properties (Hirat and Suga 1983).
Plant
Sterols These
include Campesterol, f3 Sitosterol and Lupeol (Coats 1979).
Sallcylic acid
This
is an aspirin-like compound possessing anti-inflammatory and
antibacterial properties. Topically, it has a kerolytic effect which
helps to debride a wound of necrotic tissue.
Amino acids
These are the
building blocks of proteins. Aloe vera gel provides 20 of the 22
necessary amino acids required by the human body and seven of the
eight essential amino acids which the body cannot synthesize. These
must be ingested in food.
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What
makes Aloe Vera work?
It is
surprising that the evident healing effects of aloe vera can be
produced by such a small quantity of solid material. Some people
believe that there is a synergistic action between all the component
ingredients, giving a result which is greater than the sum of the
individual actions. The combined action of all herbal preparations
taken from whole stems, roots, leaves or fruits containing huge
numbers, but very small amounts of phyto-chemicals, stretches the
boundaries of the conventional medicinal paradigm.
In all allopathic
(orthodox) medicine, the practice is to isolate, in a chemically
pure form, the biologically active substance of the constituent ingredients. These extracted drugs must be uniform in their
composition in order to demonstrate a consistent physiological
effect. Perhaps there is some truth in an ancient Ayurvedic text
from India: ‘Extracting drugs from a part of the plant is taking
out the intelligence and throwing away the wisdom.’ Whole plant
preparations, though less potent, are generally considered to be
safer with fewer side effects.
The evidence suggests
that the primary sites of action for aloe vera are:
-
Epithelial tissues
— the epithelium is the layer of cells which covers the
surface of the body or lines a cavity that communicates with
the surface. The skin, the largest organ of the body, is also
the largest epithelial surface — but other epithelial tissues
line the nose, sinuses, lungs, mouth, oesophagus and alimentary
tract, as well as the genital tract. This action on surfaces and
membranes, rather than solid organs, may account for some of
the healing properties of aloe vera (Davis et al 1987, Fulton
1990, Heggers 1996).
-
The immune system
— here, aloe vera exerts an effect on the cytokine system,
resulting in immunomodulation (Green 1996, Marshall et al 1993,
Winters 1993). In the US, the polymannose sugar has been
extracted by Carrington Laboratories and its product, Carrisyn,
has been licensed to treat the onchogenic retroviral infection
which causes leukaemia in cats. It is currently being tn-aIled in
human retroviral infection (AIDS) where it has been found to be
synergistic with Zidovudine.
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Burns
and leg ulcers
Aloe vera
appears to speed up the healing of damaged epithelial tissue in
burns
and leg ulcers by:
-
Providing
essential micronutrients
-
An
anti-inflammatory effect
-
An antimicrobial
effect
-
The stimulation of
skin fibroblasts (Danhoff and McAnally 1983).
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Should
it be taken internally or applied topically?
Aloe vera can be taken internally as a drink or applied topically.
The principle ingredient of any product should be the stabilised
aloe vera gel which is as near to the inner gel of the natural plant
as possible. It must not, therefore, be treated with excessive heat
or filtered during the manufacturing process, as this destroys or
reduces the effect of certain essential compounds, such as the
enzymes and polysaccharides. Regrettably there are many products
which contain virtually no aloe and yet are marketed as though they
do. Caution applies particularly to cheap capsules of dried aloe
leaf.
Not only does aloe
vera provide nutrition and pro-duce an anti-inflammatory action, it
also has a wide range of antimicrobial activity. In-vitro
experiments have been carried out on numerous organisms and have
regularly shown that, in normal strength, aloe vera is either
bactericidal or bacteriostatic against a number of common wound
pathogens.
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References
-
Coats BC (1979) The
Silent Healer, A Modern Study of Aloe Vera. Texas, Garland
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Danhoff IE, McAnally
BH (1983) Stabilised Aloe Vera, its effect on human skin cells.
Drugs in the Cosmetics Industry. 133, 52-196
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Davis RH Kabbani JM,
Moro NP (1987) Aloe Vera and wound Healing. Journal of the
American Podiatric Medical Association. 77, 4, 165-169
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Fulton JE (1990) The
Stimulation of postdermal abrasion wound healing with stabilised
Aloe Vera gel – polythylene oxide dressing. Journal of
Dermatological and Surgical Oncology, 16, 5, 460-467
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Green P (1996) Aloe
Vera extracts in equine clinical practice. Veterinary Times,26, 9.
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Heggers JP (1996)
Beneficial Effect of Aloe on wound healing in an excisional wound
healing model. Journal of Alternative and Complementary Medicine.
2, 2, 271-277
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Hirat T, Suga T
(1983) The efficiency of aloe plants, chemical constituents and
biological activities. Cosmetics and toiletries. 98, 105-108
-
Kahlon JB et al
(1991) Inhibition of Aids Virus replication by Ace Mannan in
vitro. Molecular Biothermy. 3, 127-135.
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Lorenzetti LJ et al
(1964) Bacteriostatic property of Aloe Vera. Journal of the
Pharmaceutical Society. 53, 1287-1290.
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Marshall GO, Gibbons
AS, Parnell LS (1993) Human cytokines induced by ace Mannan.
Journal of Allergy of clinical immunology. 1, 4, 505-509.
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Mckeown E (1987)
Anthraquinones and anthracenic derivatives absorb UV light.
Cosmetics and toiletries. 102, 64-65
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Obata M et al (1993)
Mechanisms of anti-inflammatory and anti thermal burn action of
carboxypeptidase from aloe aborescens miller. Natalensis berger in
rats and mice Physiotherapy research, 7, special issues, 530-533
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Sheets MA et al
(1991) Studies of the effect of ace Mannan on retrovirus
infections, clinical stabilisation of feline leukemia virus
infected cats. Molecular Biothermy. 3, 41-45
-
Shelton MS (1991)
Aloe Vera, its chemical and therapeutic properties. International
journal of dermatology. 30, 679-683.
-
Sims P Ruth M,
Zimmerman ER (1971a) Effect of Aloe Vera on Herpes simplex and
herpes virus (strain Zoster). Aloe Vera of American Archives, 1,
239-240
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Sims P, Ruth
M, Zimmerman ER (1971b) The effects of Aloe Vera on Mycotic
organism (fungi). Aloe Vera of American archives, 1, 237-238
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Strickland FM et al (1993) Prevention of
Ultraviolet radiation and induced suppression of contact and
delyed hypersensitivity by Aloe Barbadensis gel extract. Journal
of investigative dermatology. 9, 6, 197-204
-
Winters WD (1993) Immuno-reactive
lectins in leaf gel form from aloe Barbadensis Miler.
Phytotherapy Research 7, S23-25
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