The healing work of aloe vera

The juice of the leaf of Aloe barbadensis (aloe vera) is an important ingredient of griffin+row’s Cleanse – skin cleanser, Nourish- natural skin moisturiser and Enrich- antioxidant night cream. This short, thick-leaved plant has an enviable record of use for thousands of years. While it has been a favourite household remedy for skin ailments and upset digestive tracts in Africa, Asia and some parts of the Mediterranean, the practitioners of modern medicine are still puzzling over its succulent leaves trying to fathom why it has such a profound healing effect 1. Happily for the rest of us, ever since it has become clear that there are no sustained adverse reactions, we are quite content with the great results of its use on our skin!

Introducing Aloe barbadensis

The aloe resembles the agave in that it has thick leaves and no stem. There are about 360 different varieties of the plant, mostly found in Madagascar and south-eastern Africa. The most common species is Aloe barbadensis (also referred to as Barbados aloe, Curacao aloe, Indian aloe or Chinese aloe). The plant is synonymous with Aloe vera, which derives its name from ‘alloeh’ an Arabic term that means ‘shining and bitter’ presumably referring to the thick gel contained in its leaves 2. The species name ‘vera’ is Latin for ‘true’ in order to identify the correct plant that has medicinal properties. Common names for the plant include ‘Burn plant’ and ‘First aid plant’, thanks to its healing properties 3.

The short, hardy, perennial succulent is thought to be native to the southern part of the Arabian Peninsula, eastern and southern Africa, the Canary Islands and Spain 4. It may have arrived in India and China much earlier than the Mediterranean and West Indies. Today, aloe is grown worldwide. Not a fussy plant, it will grow anywhere except where the temperature plunges to below 0°C and in water-logged soil. In fact, in Sanskrit Ayurvedic texts, one of the adjectives used to describe the aloe is ‘amara’ (immortal).

Traditional uses of Aloe barbadensis

The Aloe has been described in great detail by native medicinal systems of the ancient Egyptians, Greeks, Chinese, Indians, Persians and Arabs.

The Egyptians referred to aloe as the ‘plant of immortality’. Carved on temple walls, the plant was an important ingredient in potions made in offering to the goddess Isis and the sun god Ra. In the Ebers papyrus, the aloe plant has been described in detail with its various uses, especially in the context of mummification of the dead. The plant has also been found placed at the entrance of pyramids built over interred Pharaohs. Aloe vera gel is supposed to have been added to the famous milk-baths of Nefertiti and Cleopatra to enhance their beauty 5.

Sumerian clay tablets dated circa 1750 BC depict the aloe plant with and without its flowers 5. It is thought that the Arabs brought the aloe to India. Yet, there is undisputed evidence of the mention of the plant as ‘Ghritakumari’ and its healing properties in the ‘Bhela Samhita’- an ancient treatise on Ayurveda written in the 6th century BC- long before the advent of the Arabs into the sub-continent 6. Some scholars even claim that the plant is mentioned in the Rgveda (circa 5000 BC) 7, although this is debatable. Ayurveda also describes the use of ‘Kumari’ which is aloe vera gel as a base for several medicines.

The aloe has been mentioned at least five times in the Bible as an unguent for rituals prior to burial or for application of myrrh 5.

Aloe was highly prized (though apparently not found) in Greece. Aristotle, the mentor of Alexander of Macedonia, exhorted him to capture the island of Socotra (now a part of Yemen) in the Indian Ocean to obtain aloe for wound healing in soldiers. The plant was later described in some detail in Dioscorides’ de Materia medica (circa 1st century AD) and Pliny the Elder’s Historia Naturalis for the treatment of wounds and skin disorders, digestive problems and headaches.

In traditional Persian medicine systems, aloe gel was used extensively in wound healing and taken internally to cure afflictions of the digestive system 8.

Traditional Chinese medicine also describes the use of aloe (called “Lu Hui” in Mandarin) along with other herbs to treat digestive problems, irritability, insomnia, convulsions and epilepsy 9.

It was only in the 1500s that aloe was introduced to northern Europe with a translation of Dioscorides’ de Materia Medica. Unfortunately, much of the value in the Materia medica was lost in translation into northern European languages 10. In addition to this, the plant did not grow in the cold northern winters and aloe extracts did not retain their activity. The wonder of aloe diminished and the plant fell into disfavour in Europe. Following global colonisation by Europeans and the suppression of indigenous knowledge, aloe was lost to the medical world.

The first revival of interest in aloe was in the 1950s, when it was used to treat burns caused by radiation therapy in the United States 11. Now, with renewed interest in alternative medicine, aloe has been subject to systematic studies with respect to its wound healing capabilities. To date there are isolated reports of biological activity. However, reliable scientific evidence is hard to come by since most studies have non-standard sources of the juice or gel. And so while there is plenty of empirical evidence of the efficacy of aloe, the plant is still a scientific enigma. 

Bioactivity and associated components of the plant

The thick succulent leaves of the aloe contain all its bioactive molecules. Harvesting the leaves releases a light yellow coloured exudate called the latex or ‘juice’. The ‘juice’ contains the anthraquinone aloin and its related compounds barbaloin and isobarbaloin.

The mucilaginous glucomannan-rich pulp from the centre of the leaf is referred to as the ‘gel’. The runny gel (it is composed of 95% water) also contains several vitamins, enzymes, minerals, amino acids and other bioactive compounds.

The following classes of compounds are found in the total leaf extract 11

  • Anthraquinones: Aloin, barbaloin, isobarbaloin, anthranol, barbaetic acid, ester of cinnamic acid, emodin, chrysophanic acid, resistannol
  • Vitamins: B1(thiamine), B2 (riboflavin), B6 (pyridoxine), choline, folic acid, vitamin C, vitamin E and beta-carotene

  • Amino acids: Histidine, alanine, hydroxyproline, proline, glycine, aspartic acid, glutamic acid and tyrosine
  • Essential amino acids: Methionine, lysine, threonine, valine, leucine, isoleucine and phenylalanine
  • Minerals: Sodium, calcium, phosphorus, iron, copper, zinc, magnesium, manganese and chromium
  • Enzymes: Bradykinase, alkaline phosphatase, catalase, peroxidase, alliinase, lipase and cellulase
  • Sterols: Campesterol, sitosterol and lupeol.
  • Others: Salicyclic acid, lignin, saponins, lectins, arachidonic acid and gibberellin.

Aloin, alprogen and C-glucosyl chromone: a spotlight on the main bioactive components

  • Aloin is an anthraquinone.

Aloin is the active ingredient in aloe that, along with another anthraquinone emodin, contributes to the analgesic, antibacterial and antiviral property of the plant extract. If taken internally, aloin also acts as a laxative 11.

  • Alprogen is a glycoprotein.  

A small protein with sugars attached to it, alprogen from aloe plant extract has been found to have potent anti-allergic actions 12.

  • C-glucosyl chromone is a substituted benzopyran with ketone groups.

C-glucosyl chromone from aloe has a chromone backbone with a sugar (glucose) attached to it. It has been shown to have anti-inflammatory actions 13.

General health benefits and uses of Aloe barbadensis:

Aloe has been used down the ages for ailments ranging from acne to alopecia, from digestive ailments to diabetes. Logically it is easy to correlate the presence of some compounds in the leaf to the effect they may have. For example, total leaf extract has been shown to have a hypoglycaemic effect in animals. The presence of lectins– sugar binding proteins- in the extract could account for this anti-diabetic activity. Due to lack of hard evidence, aloe has not been included in specific prescription medicines. However, since it has been consistently shown to be hypoallergenic it is being used with increasing popularity, especially in topical applications, for the following properties-

  • Moisturising and anti-ageing effects: The mucopolysaccharides in aloe vera gel help in binding and retaining moisture while lignin gives it deep penetration. The amino acid- rich gel softens the skin and zinc tightens pores. Topical application of the gel increases collagen generation and, more significantly, the percentage of collagen type III. The level of crosslinking in collagen has also been observed to increase. Increased crosslinking leads to tighter skin texture, indicating that the gel may be useful in slowing down the formation of wrinkles and sagging in ageing skin 11.
  • Antiseptic effects: Lupeol, salicylic acid, cinnamomic acid, phenols and sulphur compounds in aloe have antibacterial and antiviral effects 11.
  • Anti-allergic action: A glycoprotein called alprogen isolated from aloe extract has been shown to inhibit the release of histamine from mast cells which triggers allergic reactions 12.
  • Anti-inflammatory and anti-oxidant action: The C-glucosyl chromone isolated from aloe gel has shown potent anti-inflammatory properties by inhibiting the cyclooxygenase pathway and reducing the inflammatory prostaglandin E2 from arachidonic acid. This chromone may also be partly responsible for the anti-oxidant activity of aloe vera gel 13.
  • Anti-acne effect: The saponins in aloe vera have a gentle cleansing action. Along with the action of anthraquinones, salicylic acid and lupeol, aloe keeps the pores of the skin free of dirt and acne-causing bacteria.
  • Wound healing: Aloe has earned the sobriquet of ‘First aid plant’ because of its ability to hasten wound healing and reduce scarring. It has been shown that the plant contains the enzyme bradykinase which helps to reduce inflammation. Glucomannan and gibberellin act on the receptors of skin fibroblasts to accelerate wound healing. It has also been reported that topical application triggers increased collagen III production as well as hyaluronidase and dermatan sulfate synthesis, which are important in the shrinking and breaking down of scar tissue 11.
  • Burn healing: Aloe vera gel compares with silver sulfadiazine or framycetin creams in healing burns 14.
  • Healing of radiation burns: Studies on post-radiation burns in patients who have undergone radiation therapy have confirmed the soothing action of the gel on such burns. It is thought that an anti-oxidant protein – metallothionein (a metal binding protein) is generated in the skin and that the enzymes like catalase and peroxidase scavenge damaging free radicals generated due to the ionising radiation 11.
  • Laxative effect: The anthroquinones present in the juice of the aloe leaf are responsible for the laxative action when taken orally 11.

Use in the cosmetic industry:

Aloe has been used extensively in cosmetics, especially in regenerative creams such as anti-ageing and anti-wrinkle gels. Lotions with the aloe gel base are recommended for dry skin, allergies and acne-prone skin.

Botany and grow it yourself

The Aloe belongs to the Liliaceae family. Aloe barbadensis is a short plant that grows to an average height of 12-15 inches. When cultivated in fields, the plants can reach a height of 26-28 inches. In the absence of a stem, the leaves rise in a rosette fashion directly from the ground. The thick triangular leaves with serrated, spiny edges are tapered at the top. They are greyish-green to light green in colour with a sprinkling of white spots 4.

The plant bears orange -yellow coloured flowers in the winter of the second year after planting. The flowers are arranged in spikes and rise above the leaves. Most of the species are male that are sterile or with very few pollen. The plant reproduces by vegetative propagation, with the appearance of small rosettes along the rhizome of the parent.

To grow aloe, one needs well-drained soil and a warm temperature. Aloe does not have a deep penetrating root system and can be easily cultivated in shallow pots. It is imperative to prevent flooding since excess water is one of the two reasons that aloe will not thrive (the other being freezing temperature). Aloe is naturally pest- resistant and can be grown as an indoor plant 4.

In order to extract the gel, 4-6 leaves of a mature plant can be harvested every 6 weeks. The spines on the edge and tip are removed after washing the leaf. The juice is allowed to flow out into sterile containers. Transverse slits are then made on the leaf and the inner gel is scraped out.

Glossary

Anthraquinones: These are organic molecules with three fused rings, with two ketone groups in the central ring. Anthraquinones are synthesised by plants, fungi and some insects. Synthetic dyes have an anthraquinone backbone.

Collagen: Collagen is a structural protein that literally holds the body together. The main component of connective tissue, different forms of collagen are found in bone, cartilage, tendons, ligaments, muscle and skin. Collagen crosslinking forms a mesh, which acts as a supporting framework on which cells rest in layers. When the crosslinking is weak (as with ageing) or breaks (as with an injury) there is a puckering effect. Wrinkles are caused by sagging collagen in the skin.

Chromone: Chromones are complex compounds found in plants which are associated with potent biological activity including anti-oxidant, anti-allergy and anti-cancer and anti-inflammatory activity.

Essential amino acids: Amino acids that the body cannot synthesise and therefore, must be obtained from the diet are called essential amino acids. Humans depend on their food for nine essential amino acids – lysine, histidine, tryptophan, phenylalanine, threonine, valine, leucine, isoleucine and methionine.

Saponins: Saponins are structurally amphipathic glycosides that have a soap-like activity. They are found in abundance in some plants like Acacia spp. and Sapindus spp. which have been used from centuries as natural cleansing agents.  


References and Sources

  1. Vogler BK and Ernst E. (1999). Aloe vera: a systematic review of its clinical effectiveness. British Journal of General Practice 49: 823-828.
  2. Haque MZ, Islam MB, Jalil MA and Shafque MZ. (2014).Proximate analysis of Aloe vera IOCR Journal of applied chemistry. 7(6): 36-40.
  3. Nandal U and Bharadwaj RK. (2012). Aloe vera– a valuable wonder plant for food, medicine and cosmetic use- a review. International journal of pharmaceutical sciences review and research. 13(1):59-67.
  4. Farooqui AA and Sreeramu BS. (2001). “Aloe”. In “Cultivation of medicinal and aromatic crops”. Universities Press (India) Ltd. pp 22-26.
  5. Aloe vera’s 4000 year old history. (2017). Retrieved from http://www.desertharvest.com/av-history.html (7th July, 2017)
  6. Dhiman S, Kumar A, Dhiman M, Chawla KS and Priyanka. (2017). Review of Kumari (Aloe barbadensis. Miller) in Ayurvedic literature. International Journal of Ayurveda Pharmacology and Chemistry. 6 (1): 224-237.
  7. Doshi KA, Patel MH and Kadambari RK. (2015). Kumari (Aloe vera Tourn ex. Linn) a miraculous herb on earth – a classical review. International journal of ayurvedic and herbal medicine. 5(3): 1754-1764.
  8. Farzaei HM, Abbasabadi Z, Reza S-A M, Abdollahi M and Rahimi R. (2014). A comprehensive review of plants and their active constituents with wound healing activity in traditional Iranian medicine. Wounds. 26(7):197-206.
  9. Aloe vera gel. (2016). Retrieved from http://www.chineseherbshealing.com/aloe-vera-gel/ (10th July, 2017).
  10. Riddle JM. “Dioscorides”. Pp 8-11. Retrieved from http://catalogustranslationum.org/PDFs/volume04/v04_dioscorides.pdf (10th July, 2017).
  11. Surjushe A, Vasani R and Saple DG. (2008). Aloe vera: A short review. Indian Journal of Dermatology53(4), 163–166.
  12. Ro JY, Lee BC, Kim JY,  Chung YJ, Chung MH, Lee SK, Jo TH, Kim KH and Park YI. (2000). Inhibitory mechanism of Aloe single component (Alprogen) on mediator release in Guinea Pig lung mast cells activated with specific antigen-antibody reactions. Journal of Pharmacology and Experimental Therapeutics. 292 (1): 114-121.
  13. Hutter JA, Salman M, Stavinoha WB, Satsangi N, Williams RF, Streeper RT and Weintraub ST. (1996). Antiinflammatory C-glucosyl chromone from Aloe barbadensis. Journal of natural products. 59(5): 541-543.
  14. Maenthaisong R, Chaiyakunapruk N, Niruntraporn S, Kongkaew C. (2007). The efficacy of aloe vera used for burn wound healing: a systematic review. Burns. 33(6): 713-718.