Friday's Botanical: Aloe vera

BOTANICAL NAME/FAMILY

·        Aloe vera (L.)/Aloe barbadensis (Mill.) (family Aloeaceae)

OTHER NAMES

·        Aloes, Barbados aloe, Curacao aloe

PLANT PARTS USED

·        leaf

CHEMICAL COMPONENTS

·        Aloe vera extract, or diluted aloe gel, is made of mostly water (99%) and mono- and polysaccharides, the most important of which are the monosaccharide mannose-6-phosphate and the polysaccharide gluco-mannans, which are long-chain sugars containing glucose and mannose. Gluco-mannan has been named acemannan and is marketed as Carrisyn. A glycoprotein with anti-allergic properties has also been isolated, and has been named alprogen. Recently, C-glucosyl chromone, an anti-inflammatory compound, has also been identified.

·        Aloe gel also contains lignans, saponins, salicylic acid, sterols and triterpenoids, vitamins A, C, E, B₁₂, thiamine, niacin and folic acid, and the minerals sodium, calcium, potassium, manganese, magnesium, copper, chromium, zinc and iron

MAIN ACTIONS                       

·        The active ingredients, whether acting alone or in concert, include glycoproteins, anthraquinones, polysaccharides, and low-molecular-weight species such as beta-sitosterol. 

·        Assists in wound healing

Wound healing is associated with various mechanisms and constituents. Thromboxane inhibits wound healing and aloe has been shown to inhibit thromboxane in vitro. Enzymes in aloe have also been shown to break down damaged tissue, which can then be removed by phagocytosis. A glycoprotein fraction was found to increase proliferation of human keratinocytes and increase the expression of receptors for epidermal growth factor and fibronectin in vitro. The same research team then demonstrated that this glycoprotein enhanced wound healing by increasing cell proliferation in vivo. Beta-sitosterol appears to improve wound healing by stimulating angiogenesis and neovascularisation in vivo. Aloe polysaccharides have been shown to ameliorate UV-induced immunosuppression.

Other actions include

·        Anti-oxidant, immunostimulant, anti-inflammatory, laxative, anti-ulcer, hypoglycaemic, antimicrobial, antiviral.

DOSAGE RANGE

·        Aloe vera gel: fresh from a living plant or as stabilised juice 25 mL (4.5:1) up to four times daily.

·        Extracts standardised to acemannan: preparation containing up to 800 mg/day.

·        Topical application: gel, cream or ointment as needed.

·        1.5–4.5 mL daily of 1:10 tincture of resin (latex).

ADVERSE REACTIONS

·        Although adverse reactions are rare, hypersensitivities and contact dermatitis to aloe have been.  Hypersensitivity manifested by generalised nummular eczematous and papular dermatitis, and presumably by contact urticaria, developed in a 47-year-old man after 4 years of using oral and topical aloe. Patch tests for aloe were positive in this patient.

SIGNIFICANT INTERACTIONS

·        Hypoglycaemic agents

o       Oral A. vera may have hypoglycaemic activity, therefore additive effects are theoretically possible— observe patients taking this combination.

·        Laxatives

o       Additive effects are theoretically possible with oral aloe latex inducing griping pains. Use with caution.

·        Topical cortisone preparations

o       In addition to its own anti-inflammatory effects, animal studies have shown that A. vera increases the absorption of hydrocortisone by hydrating the stratum corneum, inhibits hydrocortisone’s suppressive effects on wound healing and increases wound tensile strength — possible beneficial interaction.

·        Vitamins C and E

o       Concurrent prescription of oral A. vera (both gel and latex) with vitamins C and E shows improved absorption and increased plasma life of vitamin concentration for both vitamins when taken together.

CONTRAINDICATIONS AND PRECAUTIONS

o       Strong laxatives such as aloe latex are contraindicated in children. Avoid in patients with known hypersensitivity to aloe or with nausea, vomiting or signs and symptoms of gastrointestinal obstruction. Avoid excessive use and long-term use (more than 2 weeks), as potassium losses may occur, which may alter cardiac electrophysiology.

o       Use with caution in people with thyrotoxicosis.

PREGNANCY USE

o       Strong laxatives such as aloe latex are traditionally contraindicated in pregnancy. Scientific evidence is unavailable to conclusively support the safe use of orally administered aloe.