Ericaceae

Arctostaphylos uva-ursi

Arctostaphylos uva-ursi (bearberry) contains a steroid, sitosterol, and triterpenoids, such as amyrin, betulinic acid, lupeol, oleanolic acid, taraxenol, ursolic acid, and uvaol. The main constituent is a glucoside called arbutin. Other constituents are methylarbutin, ericolin, ursone, gallic acid, and ellagic acid.

The reputed antibacterial activity of uva-ursi is ascribed to the urinary metabolite hydroquinone, which is excreted in the form of inactive conjugates and needs an alkaline urine to be liberated. As the urine of people who consume a Western non-vegetarian diet is usually acidic, it is sometimes suggested that one should alkalinize the urine of bearberry users with sodium bicarbonate. However, as the dosage recommended for this purpose is usually high, this carries well-known risks such as a high sodium load and interference with the renal clearance of certain other drugs. On the other hand, reports of carcinogenicity of hydroquinone after prolonged administration of high doses to rats or mice raise a question about the long-term safety of uva-ursi and other medicinal herbs that contain substantial amounts of arbutin [ ].

A 56-year-old woman who had taken uva-ursi for 3 years developed reduced visual acuity [ ]. She had a typical bull’s-eye maculopathy bilaterally. The authors suggested that the effect was due to impaired melanin synthesis.

The urine of patients taking bearberry can darken on standing.

Gaultheria procumbens

The volatile oil of Gaultheria procumbens (wintergreen) leaves consists largely of methyl salicylate (more than 95%).

Salicylism has been attributed to the use of oil of wintergreen as part of an herbal skin cream for the treatment of psoriasis [ ].

• A 40-year-old man became acutely unwell after receiving oil of wintergreen from an unregistered naturopath. Transcutaneous absorption of the methyl salicylate was enhanced in this case owing to the abnormal areas of skin that were covered and the use of an occlusive dressing. The patient developed tinnitus, vomiting, tachypnea, and the typical acid/base disturbance of salicylate toxicity. Decontamination of the skin followed by rehydration and establishment of good urine flow was successful.

Laryngeal edema has been attributed to oil of wintergreen [ ].

Methyl salicylate in topical analgesic preparations can cause irritant or allergic contact dermatitis and anaphylactic reactions [ ].

In a retrospective study 80 subjects who had taken aspirin tablets (n = 42) or topical oil of wintergreen (n = 38) were compared [ ]. The admission plasma salicylate concentrations were generally higher in those who had taken aspirin tablets, but the two highest readings (4.3 and 3.5 mmol/1) belonged to two of the subjects who had taken oil of wintergreen.

Oil of wintergreen in the form of candy flavoring was ingested by a 21-month-old boy who developed vomiting, lethargy, and hyperpnea but recovered rapidly with parenteral fluids and sodium bicarbonate [ ].

Methylsalicylate is also an important constituent of the Red Flower Oil formulations that are popular herbal analgesics for topical application in Southeast Asia. Some users take small amounts of the oil orally to enhance its analgesic effects. There are many different brands, which provide variable amounts of declared or undeclared methylsalicylate (up to 0.78 g/ml of oil). A suicide attempt by deliberate ingestion of about 100 ml resulted in severe salicylate poisoning [ ].

Ledum palustre

The essential oil of Ledum palustre (marsh Labrador tea), which contains flavones, monoterpenoids, and sesquiterpenoids, is a potent irritant of the gastrointestinal tract, kidneys, and urinary tract; other toxic effects include abortion.