The vasodilatory effects of medicinal herbs on the cardiovascular system: A systematic review

Vasodilators are drugs that induce or start the widening of blood vessels and are commonly applied to treat disorders with irregularly high blood pressure, including hypertension, congestive heart failure, and angina. The present study aims to systematically review the studies on the vasodilation effects of medicinal herbs. The study was done according to the 06- Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines and registered in the CAMARADES-NC3Rs Preclinical Systematic Review and Meta-Analysis Facility (SyRF) database. Various English databases, such as Scopus, PubMed, Web of Science, EMBASE, and Google Scholar, were used to find publications about the vasodilation effects of medicinal herbs with no date limitation. The searched terms and keywords words were: "medicinal herbs", "medicinal plants", "vasodilator", "vasorelaxant", "hypertension", "high blood pressure", "vasodilation", "extract", "essential oil". Out of 1820 papers (up to 2020), 31 papers met the inclusion criteria and were reviewed. The most important medicinal plants with vasodilation/vasorelaxant activity belonged to the family Asteraceae (19.4%) followed by Zingiberaceae (9.7%). Aerial parts (30.5%), leaves (30.5%), followed by roots (11.1%) were the most common parts used in the studies. The findings showed that ethanolic extract (33.3%), followed by aqueous extract (22.2%) and methanolic extract (19.4%) was the frequency used extraction methods, whereas the essential oil (13.9%) and hydroalcoholic extract (8.3%) were the second most used herbal remedies. The results of the current review study revealed that the plant vasodilatory agents were might be used as an alternative and complementary source to treat hypertension as they had lower important toxicity. Nevertheless, more investigations, particularly clinical trials, are needed to clear this suggestion.