Arbor vitae (Thuja occidentalis L.) is a native European tree widely used in homeopathy and evidence-based phytotherapy. Many reviews and monographs have been published on the herbal substance's description, mode of action and clinical use. However, no comprehensive evidence-based review is available. Therefore, our aim was to search MEDLINE databases and survey manufacturers for further details or unpublished data. This review presents the botany, ethnobotany and phytochemistry, especially the different contents of essential oil (Thujone) in relation to different extraction procedures of this medicinal plant. Thuja's antiviral action and immunopharmacological potential, such as stimulatory and co-stimulatory effects on cytokine and antibody production and activation of macrophages and other immunocompetent cells, have been evaluated in numerous in vitro and in vivo investigations. Although no controlled trials have been conducted on Thuja occ alone, many clinical studies have been performed with a herbal medicinal product containing a special extract of Thuja occ and other immunostimulants, demonstrating its therapeutic efficacy and safety in respiratory tract infections.

Endocrine therapy in breast cancer survivors can cause severe 'climacteric' symptoms, which may compromise therapy adherence. To determine whether such symptoms can be treated with herbal medication containing black cohosh in the form of isopropanolic Cimicifuga racemosa extract (iCR) alone or in fixed combination with St John's wort (Hypericum perforatum [HP]) (iCR þ HP), a systematic literature search was conducted. Results were viewed in relation to experimental data and metabolism of endocrine therapies. Most breast cancer survivors receiving endocrine therapy experienced reductions in climacteric symptoms under iCR/iCR þ HP. Tamoxifen's interference potential may be countered by using higher iCR doses or iCR þ HP. No estrogen-like effects at the breast or on hormones were seen. After breast cancer, even if receiving tamoxifen, patients using iCR/iCR þ HP had significantly increased recurrence-free survival rates compared to non-users. These results are substantiated by experimental data demonstrating antiproliferative and anti-invasive effects of iCR in breast cancer cells and enhancement of the antineoplastic effects of tamoxifen. There are no known clinical interactions for iCR and HP with endocrine therapies. The HP extract used in iCR þ HP did not exhibit any clinically relevant interaction potential. In conclusion, with its positive benefit-risk profile, iCR/iCR þ HP may offer a safe non-hormonal therapeutic option for breast cancer survivors receiving endocrine therapy.

Uva-ursi folium (bearberry leaf) has been traditionally used to treat symptoms of lower urinary tract infections. The most representative constituent of this herbal drug is arbutin that is rapidly absorbed in the small intestine and undergoes hepatic conjugation to form hydroquinone (HQ) conjugates. As free HQ is crucial for the safety of the herbal preparation, we reviewed published and unpublished experimental and human studies to clarify some outdated assumptions and to support the safety of therapeutic daily doses of Uva-ursi folium extract. Specifically, data on pharmacokinetics and the human exposure of arbutin and HQ were reviewed. A therapeutic recommended human daily dose of bearberry leaf extract (420 mg hydroquinone derivatives calculated as anhydrous arbutin) liberates free HQ in urine at a maximum exposure level of 11 µg/kg body weight (bw)/d. By means of an experimental no observed effect level value, a permitted daily exposure dose below which there is a negligible risk to human health was estimated for free HQ (100 µg/kg bw/d). Dietary sources of arbutin/HQ that are regularly consumed long term by humans generate comparable free HQ exposure levels. There is no direct evidence, regarding human data, supporting the fact that free HQ causes convulsion, hepatotoxicity, nephrotoxicity, or promotion of tumors in humans. Free HQ had no activity promoting pancreatic, bladder, stomach, or liver carcinogenesis. In conclusion, under the recommended use conditions Uva-ursi folium is a safe therapeutic option for treating lower urinary tract infections.

The results of this meta-analysis of five randomized, double-blind, and controlled clinical trials showed no evidence that iCR has any adverse effect on liver function.

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