Aloe Vera

Michelle Giesler and Kimberly Jones

I. General Description

     A. Location: dry regions of Africa, Asia, Europe, and America

     B. Plant Characteristics:

• touch, fleshy, spearlike or triangular leaves rising in a rosetteconfiguration; as many as 30 leaves per plant; sawlike leaf margins; leaf is filled with gel  from a central, clear mucilaginous pulp; plant grows to 1.5 to 4 feet high. Of the 200 +  species of Aloe Vera, 4 have nutritional value, and Aloe Barbendisis Miller is the most common

     C. Part harvested for medicinal effects: LEA

• Latex (corrugated lining containing bitter juice): laxative properties
• Gel (central parenchymal tissue): other applications

II. Chemical Composition

     A. Active Compounds

1. Anthraquinones (aloin, barbaloin, aloe-emodin): cathartics
2. Saccharides (acetylated mannose): antiviral and immunopotentiating action
3. Prostaglandins and fatty acids (gamma-linoleic acid....prostaglandin 1 series): favorable effects on inflammation, allergy, platelet aggregation, wound healing
4. Others: enzymes, amino acids, vitamins, minerals

     B. Other Compounds:

• cholesterol, triglycerides, steroids, uric acid, lignins, beta-sitosterol, glibberellin, salicylic acid

III. History and Folk Use

• Mesopotamia (1750 BC), Egypt (550 BC), and Greeks (23 AD): wound healing and treatment for skin infections
• US Pharmacopoeia (1820): laxative
• US (1935): treatment of burns, skin ulcers, and minor irritations

IV. Pharmacology

Antibacterial and antifungal

• 60% extract: bactericidal against Pseudomonas a., Klebsiella p., Serratia m., Citrobacter, Enterobacter c., Strep. Pyogenes and agalactiae
• 77% extract: bactericidal against Staph. a. 80% for E. coli, 90% for Strep. f. and Candida a.
• Inhibition of growth: Mycobacterium 5., Trichophyton, and Bacillus subtilis

Antiviral: acemannan

• Direct antiviral activity against HIV1 by inhibiting glycosylation of viral glycoproteins
• Acts synergistically with AZT or acyclovir by inhibiting the replication of HIV and HSV1
• Also effective against feline leukemia, influenza, and measles

Immune enhancement: acemannan

• Enhancement of macrophage activity, release of immune system potentiators, T cell function, interferon production
• Possible activity in sarcomas and spontaneous tumors

Anti-allergy and anti-inflammatory: glycoproteins and anthraquinones

• Block generation of thromboxanes and bradykinin
• Inhibit and break down bradykinin

Wound healing

• Vitamin C and E, zinc
• Stimulate fibroblast and connective tissue formation, promoting wound repair
• Stimulate repair process and epidermal growth

V. Clinical Applications

Oral: constipation, immune system enhancement, diabetes, asthma, viral infections (internal           use of Aloe Vera is not generally recommended)

Topical: wound healing (antimicrobial), burn healing (especially from radiation), frostbite             healing (vasodilation), mouth ulcer healing, anti-inflammatory, moisturizer, and emollient

VI. Toxicity

• Allergic Reactions: generalized eczematous and papular dermatitis (from topical application)
• Delaying of surgical wound healing (deep vertical wounds)
• Potent cathartic action may cause diarrhea and abdominal cramping; not recommended for use as a laxative

VII. Drug and Disease Interactions

• Pregnancy and lactation: latex should not be administered due to theoretical possibility of uterine contraction stimulation and miscarriage or cramps and violent catharsis in infants
• Any gastrointestinal illness: may aggravate ulcers, hemorrhoids, colitis, or IBS

VIII. Dosage

• Gel: apply liberally (topical)
• Juice: no more than one quart/day
• Acemannan: (HIV/AIDS) 800-1600 mg/day (0.5-1 L/day of juice)
• Oral for laxative use: 120-200 mg (but this use is not recommended)

**Look for stabilized products if the gel is not used directly from the plant**

Clincal Trials

     Miller et al. compared the therapeutic effects of systemic pentoxifylline and topical aloe vera cream in the treatment of frostbite on the ears of 10 white rabbits. The four treatment groups included untreated controls, treatment with aloe cream, treatment with pentoxifylline, and treatment with aloe cream + pentoxifylline. The control group had a 6% tissue survival, 20% with pentoxifylline, 24% with aloe cream, and 30% with combined therapy. All treatment groups had significantly improved tissue survival compared with the control ears (p<0.05), and no statistically significant difference was found among treatment groups.

     Karaca et al. examined the production of reactive nitrogen intermediates by chicken spleen cells and cells of HD11 line (chicken macrophage cell line) in response to acemannan, a complex carbohydrate extracted from aloe vera. Nitric oxide, produced by macrophages, has many effects on tissues including acting as a cytotoxic effects in the killing of tumor cells and parasites, and mediating immune regulation and host defenses in mammalian and avian species. All preparations produced detectable amounts of NO and a dose-response relationship was evident, but no p value was given.

     Davis et al. showed that aloe vera, at doses of 100 and 300 mg/kg/day for 4 days, blocked the wound healing suppression of hydrocortisone acetate up to 100% and increased tensile strength above an aqueous control, using the wound tensile strength assay (all p values < 0.005). Also, the sterols in aloe (lupeol, camp-esterol, and beta-sitosterol) proved to have significant anti-inflammatory effects and showed a dose-response relationship.

Table 1: Aloe Vera blocks the hydrocortisone Acetate inhibition on wound healing and tensile strength

Treatment (mg/kg)                                        Change in Wound Tensile Strength

• 0.01 hydrocortisone acetate                                       -26.7 +/- 2.4
• +100 aloe                                                                 +51.5 +/- 3.1
• +300 aloe                                                                 +39.4 +/- 1.7

• 0.1 hydrocortisone acetate                                         -17.8 +/- 1.0
• +100 aloe                                                                  +40.5 +/- 3.9
• +300 aloe                                                                  +24.3 +/- 2.1

• 1.0 hydrocortisone acetate                                         -46.7 +/- 6.8
• +100 aloe                                                                 +66.7 +/- 6.7
• +300 aloe                                                                 +100 +/- 7.9

Table 2: Topical Anti-Inflammatory Activity of Three Sterols Found in Aloe Vera Applied at 100 mcg Doses on Croton Oil-Induced Edema

           Sterols                                                                                          Inhibition

           Lupeol                                                                                           37.0 +/- 4.3

           B-Sitosterol                                                                                   31.1 +/- 2.9

           Campesterol                                                                                  24.2 +/- 1.9

     Tagi et al. isolated the glycoprotein fraction from aloe vera gel and tested its significance in proliferation-promoting activity on human and hamster cells in vitro. At 100 mcg/mL, 3 subfractions of the active fraction increased growth activity by 5, 20, and 27%, but no p value was given.

     Davis et al examined the possibility of mannose-6-phosphate, the major sugar in aloe vera gel, being an active growth substance. Mice receiving 300 mg/kg of mannose-6-P had improved wound healing (wound diameter decrease of 50.7%) over saline controls (42.1% reduction) with a p value < 0.01. This dose also had anti-inflammatory activity (ear weight of 5.5 mg) compared to a saline control (7.3 mg), the p value = 0.05.

References:

Castleman, M.  The Healing Herbs.  Rodale Press, Emmaus, PA.  1991.  P. 42-44.

Covington, TR, et al.  Handbook of Nonprescription Drugs.  American Pharmaceutical Association, Washington DC.  1996.  p. 231t, 234, 643, 707-708.

Davis, RH, et al.  Anti-inflammatory and wound healing activity of a growth substance in Aloe vera.  Journal of the American Podiatric Medical Association.  84(2):  77-81, 1994 Feb.

Davis, RH, et al.  Aloe vera, hydrocortisone, and sterol influence on wound tensile strength and anti-inflammation.  Journal of the American Podiatric Medical Association.  84(12):  614-21, 1994 Dec.

Dean, K.  Plant patents.  Herbalgram.  36:20.

Karaca, K., et al.  Nitric Oxide production by chicken macrophages activated by Acemannan, a complex carbohydrate extracted from Aloe vera.  International Journal of Immunopharmacology.  17(3):  183-8, 1995 March.

McCaleb, R.  Aloe Vera Compound Effect against Mouth Ulcers.  Herbalgram.  32:12.

Miller, MB, et al.  Treatment of experimental frostbite with pentoxifylline and aloe vera cream.  Archives of Otolaryngology-Head & Neck Surgery.  121(6):  678-80, 1995 June.

Murray, MD.  The Healing Power of Herbs.  Prima Publishing, Rocklin, CA.  1996.  p. 29-41.

Tyler, VE.  The Honest Herbal.  Pharmaceutical Products Press, Binghamton, NY.  1993.  p. 25-28.

Yagi, A., et al.  Isolation and characterization of the glycoprotein fraction with a proliferation-promoting activity on human and hamster cells in vitro from Aloe vera gel.  Planta Medica.  63(1):  18-21, 1997 Feb.

Web sites as follows:

http://www.aloe-vera.org/

http://www.carringtonlbs.com/

http://www.electriciti.com/aloe

http://aloe.com/aloe/