Passiflora incarnata L.: Ethnopharmacology, clinical application, safety and evaluation of clinical trials

ETHNOPHARMACOLOGICAL RELEVANCE: The genus Passiflora incarnata Linnaeus comprises approximately 520 species belonging to the Passifloraceae family. The majority of these species are vines found in Central or South America, with rare occurrence in North America, Southeast Asia and Australia. The genus Passiflora incarnata has long been used in traditional herbal medicine for the treatment of insomnia and anxiety in Europe, and it has been used as a sedative tea in North America. Furthermore, this plant has been used for analgesic, anti-spasmodic, anti-asthmatic, wormicidal and sedative purposes in Brazil; as a sedative and narcotic in Iraq; and for the treatment of disorders such as dysmenorrhoea, epilepsy, insomnia, neurosis and neuralgia in Turkey. In Poland, this plant has been used to treat hysteria and neurasthenia; in America, it has been used to treat diarrhoea, dysmenorrhoea, neuralgia, burns, haemorrhoids and insomnia. Passiflora incarnata L. has also been used to cure subjects affected by opiate dependence in India. This review aims to provide up-to-date information about the pharmacology, clinical efficacy and clinical safety of Passiflora incarnata L. based on the scientific literature. In particular, the methodological accuracy of clinical trials is analysed in accordance with current consolidated guidelines on reporting the clinical efficacy of herbal medicine, offering new insight into opportunities for future research and development. METHODS: A bibliographic investigation was performed by examining the available data on Passiflora incarnata L. from globally accepted scientific databases and search engines (Pubmed, Scopus and Web of Science, SciFinder and Google Scholar). We selected studies, case reports, and reviews addressing the pharmacology and safety of Passiflora incarnata. RESULTS: Although numerous Passiflora incarnata L. derivative products have been commercialised as alternative anxiolytic and sedative remedies based on their long tradition of use, their supposed efficacy does not appear to be adequately corroborated by the literature, with clinical studies often featuring inadequate methodologies and descriptions of the products under investigation. This medicinal plant has shown a wide spectrum of pharmacological activities in preclinical experiments, including anxiolytic, sedative, antitussive, antiasthmatic, and antidiabetic activities. The plant has a good safety profile. The clinical trials that we included in this review were designed to evaluate and in some cases confirm promising observations of preclinical pharmacological activity, and the methodological limits of these studies are characterised here. CONCLUSION: In conclusion, clinical studies on the effects of products containing herbal preparations based on Passiflora incarnata reveal crucial weaknesses such as poor details regarding the drug extract ratio, limited patient samples, no description of blinding and randomisation procedures, incorrect definition of placebo, and lack of intention to treat analysis. In conclusion, the results of this review suggest that new clinical trials should be conducted using a more rigorous methodology to assess the traditional putative efficacy of Passiflora incarnata L.