Urticaceae Stinging nettle (U. dioica); dwarf nettle (U. urens); Urtica Urticae folium/herba; Urticae radix et rhizoma Leaf/herb; root and rhizome The main constituents of the leaf are caffeic acid esters, mainly caffeoylmalic acid (not present in U. urens), chlorogenic, neochlorogenic, with free caffeic acids. Flavonoids such as kaempferol, isorhamnetin and quercetin, scopoletin, β-sitosterol and glycoprotein are also present. Histamine, serotonin, leukotriene and acetylcholine, present in the fresh plant and producing the ‘sting’, are denatured by drying (Anon. 2007; ESCOP 2003). The root contains a lectin (Urtica dioica agglutinin) composed of six isolectins, lignans including pinoresinol, (+)-neoolivil, (-)-secoisolariciresinol, dehydrodiconiferyl alcohol, 3,4-divanillyltetrahydrofuran and isolariciresinol, with polysaccharides, scopoletin, β-sitosterol and other sterols and their glucosides; caffeic acid esters, ceramides, hydroxyl fatty acids, and monoterpene diols and their glucosides (Anon. 2007; ESCOP 2003; Schöttner et al. 1997). A comprehensive review on the clinical effectiveness of nettle root extract in the treatment of BPH concluded that there is some evidence to support its use in the short term (Chrubasik et al. 2007). Most of the studies cited were open and uncontrolled, and only a small number were randomised controlled clinical trials. Since then, a small clinical study (100 patients) found that nettle extract (plant part not stated) had a better effect in relieving clinical symptoms in BPH patients compared to placebo (Ghorbanibirgani et al. 2013). More randomised trials have been performed with nettle root extracts in combination with other herbs (see e.g. saw palmetto), and these may prove more effective than nettle root extracts alone in treatment of lower urinary tract symptoms (LUTS) (Wilt et al. 2000). An open-label extension of a randomised, double-blind clinical trial assessing the effect of a fixed combination product containing saw palmetto fruit (Serenoa repens) and nettle root extract (160:120 mg per capsule, twice a day for 24 weeks) in elderly men with moderate or severe LUTS caused by BPH, showed that there was a clinically relevant benefit over a follow-up period of 96 weeks. There was a reduction in the International Prostate Symptom Score (I-PSS) self-rating questionnaire, a decrease of residual urine volume, increase in urinary flow and very few adverse events after treatment (Lopatkin et al. 2007). A combination of nettle root (U. dioica 120 mg), saw palmetto (320 mg) and pine bark (Pinus pinaster Aiton, 5 mg) extract was effective in patients suffering from LUTS when treated for periods between 1 month and a year, with or without concomitant therapy (antibiotics or alpha-blockers). In this prospective study, it was observed that patients did not present changes in flow rate and prostate volume, but a marked reduction in pain and discomfort (Pavone et al. 2010). A systematic review of herbal medicines which included U. dioica for effects on inflammatory conditions showed that there was some evidence of effectiveness in pain and the physical impairment caused by arthritis, and it reduced concurrent intake of analgesic drugs (Di Lorenzo et al. 2013). Oral preparations of nettle caused a reduction of symptoms in rheumatic conditions and were able to potentiate the efficacy of diclofenac (Anon. 2007). However, studies were limited and larger trials are needed. A randomised, double-blind study of freeze-dried U. dioica in the treatment of allergic rhinitis involved 69 patients. Assessment was based on daily symptom diaries, and global responses recorded at the follow-up visit after 1 week of therapy. U. dioica
Nettle
Urtica dioica L.; U. urens L.
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Benign prostate hyperplasia:
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