Aloe vera in wound healing

2015

Aloe vera gel is a powerful healer that has been successfully employed for millennia. It acts in the manner of a conductor, orchestrating many biologically active ingredients to achieve the goal of wound healing. Aloe can penetrate and anesthetize tissue, it is bactericidal, virucidal, and fungicidal. It possesses anti-inflammatory and immunomodulatory properties and it serves as a stimulant for wound healing, a fuel for proliferating cells and a dressing for open wounds. Although some of the independent fractions of aloe have shown unique and impressive activity by themselves, the number of different substances acting in concert serves to confirm the relative complexity of aloe’s actions. Aloe vera certainly gives scope to the phrase, ‘the whole is more than the sum of its parts.’ Since it has been difficult to postulate, separate and isolate one substance that is responsible for aloe’s capabilities, many more controlled, scientific studies must be completed before all the secrets associated with the wound-healing abilities of aloe are unlocked. Future research may be directed at further investigation of the gel’s ability to stimulate cell growth in tissue culture and its antimicrobial, antifungal, antiviral and anti-inflammatory properties.

Aloe vera is one of nature’s most revered therapeutic healing herbs. The beneficial effects of this tropical succulent have spurred recurrent legends about its properties that have persisted from the fourth century B.C. throughout world history. Even so, it has not been until recently that the scientific community has turned greater attention toward this mysterious plant extract. Scientific interest was initially triggered by a single case report of accelerated wound healing with aloe’s use in radiation-induced dermatitis of the scalp. This initial publication in 1935 and three similar cases reported shortly thereafter spurred a great deal of research investigating and detailing Aloe vera’s wound-healing abilities. In 1937, Crewe noted improvement in burn and scald wounds treated with the topical application of aloe. Mandeville in 1939 and Rowe et al. in 1941 observed an increased rate of wound healing in radiation-induced ulcer wounds. Aloe was shown to be effective in the treatment of second-degree thermal burn wounds in 1943 and in the treatment of dermal abrasions in 1947. Lushbaugh and Hale in 1953 showed accelerated wound healing and increased collagen deposition in wounds treated with aloe. In 1964, Sjostrom et al. showed increased healing in frostbite wounds, and Raine et al. in 1980 and McCauley et al. in 1983 showed increased tissue survival in frostbite wounds with the application of Aloe vera gel. In 1988 and 1989, the topical application of the gel showed improved healing in the treatment of full thickness wounds and in 1990 a commercially prepared aloe product was able to show marked improvement in wound re-epithelialization.

The complete composition of Aloe vera gel and each of its components’ effects on wound healing is still being unraveled today. Many of the abilities of the gel have already been ascribed to certain of its constituents and it is well known that Aloe vera contains many unique biologically active compounds that have wound-healing, anti-inflammatory and antimicrobial activities.

The effects of aloe vera gel on wound healing

In order to understand how Aloe vera gel effects wound healing, it is necessary to first examine its chemical composition. Working with a single compound makes it simple to develop scientific research to prove or disprove its proposed benefits. This is not the case with Aloe vera. Whereas most botanicals have a single ingredient isolated from the parent that is responsible for its observed benefits, the gel is known to contain well over 100 separate ingredients. In all aloe extracts, quite common substances make up a very large portion of the total solids including organic acids, free sugars (glucose and fructose), potassium, sodium, calcium and magnesium. Also present are fatty acids, sterols, and plant hormones called eicosanoids, terpenes, gibberellins and auxins. Together, these molecules make up 75% of the total solids in the gel.

The other 25% of the aloe extract is composed of primarily polysaccharides. A polysaccharide is a chain of simple sugars such as glucose referred to as a glucan, or mannose referred to as a mannan. Those containing two types of sugars are named accordingly, such as glucomannans or galactomannans. The physiologically active polysaccharides of Aloe and the principal component polysaccharide of the gel extract has long been recognized to be the glucomannans.

Knowing that aloe’s effect on wound healing is to do with its complex composition and the ability of its components to act in concert, it is still possible to examine each individual constituent’s effect. For more than a century, scientists have attempted to comprehend and analyze the complex interactions involved in the wound-healing process. Simultaneous interactive and mutually-dependent biochemical signaling transpires between the cellular and humoral based elements of the inflammatory response in wound healing. This signaling enables gene activation and suppression as well as organelle and tissue synthesis. It is well known that wound healing progresses through various stages, each of which involves different primary growth factors, inflammatory reactants and proliferating cells.

The topical application of a variety of cytokines and synthetic growth factors to open wounds has been a topic of many recent experiments and the results have revolutionized the understanding of the wound-healing process. The first stage of wound healing is known to involve mainly inflammatory reactants and cell types. A balance must be achieved between destroying foreign bacteria and initiating the wound-healing process. The second stage involves the proliferation of the fibroblast, which is the cell most important for laying the foundation upon which the wound will eventually gain its strength. The fibroblast can be stimulated by various growth factors and requires the availability of essential ingredients in order to produce collagen. Improved local blood flow can increase the delivery of essential ingredients and immune cells. The final stage of wound healing involves the maturation and remodeling of already existing collagen.

In short, Aloe vera gel is a modulator. It acts as both an inhibitor and a stimulator. While it can block mediators of inflammation in the immune system, it also stimulates antibody production and wound healing by growth factor-like substances. The gel factor molecule can stimulate fibroblasts to increase collagen and proteoglycan production, increasing wound tensile strength, while inhibiting inflammation and moderators of pain. Consequently, it may be the localized balance of unique substances that bestows aloe with its healing properties. Listed below and in Table Chemical Composition of Aloe vera gel is the current knowledge on the components of Aloe vera that are being investigated for their potential wound-healing properties.

Table Chemical Composition of Aloe vera gel.

Anthraquinones Inorganic compounds Vitamins
Aloin (=Barbaloin) Calcium A
Isobarbaloin Sodium B1
Anthranol Magnesium B2
Aloetic Acid Manganese B6
Aloe-emodin Chlorine C
Emodin Zinc Choline
Ethereal oil Copper Folic Acid
Resistannol Chromium Beta carotene
Potassium Alpha-tocopherol
Saccharides Enzymes Amino acids
Glucose Oxidase Lysine Aspartic acid
Mannose Amylase Valine Glutamic acid
Glucomannan Catalase Leucine Leucine
Cellulose Lipase Proline Phenylalanine
Aldopentose Alkaline Phosphatase Alanin Isoleucine
Bradykininase Tyrosine Methionine
Threonine Histidine
Glycine Arginine
Miscellaneous
Cholesterol Beta-sitosterol Lectin-like substance Eicosanoids
Fatty acids Triglycerides Uric acid Lignins
Terpenes Lupeol Campesterol Gibberellin
Salicylic acid Auxins Steroids

Aloe vera in wound healing: Gel components

 

Selections from the book: “Aloes. The genus Aloe”. Edited by Tom Reynolds. Series: “Medicinal and Aromatic Plants — Industrial Profiles”. 2004.