The biosynthesis and biotechnological production of Rosmarinic acid, a phenolic ester that is widespread in the plant kingdom, has been widely investigated. This compound has shown many remarkable biological and pharmacological activities, which have led to its pharmaceutical and analytical development, as well as clinical studies, which are summarized and analyzed here for the first time. This review compiles data from the Pubmed, Scopus, Scifinder, Web Of Science, and Science Direct databases published between 1990 and 2015, restricting the search to works with the keywords “Rosmarinic acid” in the title. The initial search identified more than 800 articles; after an initial screening and removal of duplicate works, the search was further refined, resulting in approximately 300 articles that were scrutinized and comprise this review. The articles were organized to describe extraction and isolation, analytical methods, pharmaceutical development, and biological and pharmacological activities [divided into nonclinical (in vitro, in vivo) and clinical studies], pharmacokinetic studies, and stability studies.

The present study was designed to assess the antimicrobial activity of 19 natural products belonging to terpenoids, alkaloids, thiophenes and phenolics against a panel of 14 Gram-negative multidrug-resistant (MDR) bacteria. The results demonstrated that amongst the studied compounds, alkaloids and terpenoids were less active contrary to flavonoids: neocyclomorusin (3) and candidone (6) and isoflavonoids: neobavaisoflavone (8) and daidzein (12). Thiophene, 2-(penta-1,3-diynyl)-5-(3,4-dihydroxybut-1-ynyl)thiophene (17) showed moderate and selective activities. Compounds 3, 6, 8 and 12 displayed minimal inhibitory concentration (MIC) ranged from 4 to 256 μg/mL on all the 14 tested bacteria. MIC values below 10 μg/mL were obtained with 8, 3, 6 and 12 against 50, 42.9, 35.7 and 21.4 % of the tested bacteria. The lowest MIC value of 4 μg/mL was obtained with compound 3 against Klebsiella pneumoniae ATCC11296, Enterobacter cloacae BM47, compound 6 against Escherichia coli ATCC8739, K. pneumoniae ATCC11296, E. cloacae BM47 and compound 8 against K. pneumoniae ATCC11296 and E. cloacae BM47. The activity of flavonoid 3 was better or equal to that of chloramphenicol in all tested K. pneumoniae, Providencia stuartii, E. aerogenes, E. cloacae and Pseudomonas aeruginosa strains. Within isoflavonoids, neobavaisoflavone scaffold was detected as a pharmacophoric moiety. This study indicates that natural products such as 3, 6 and 8 could be explored more to develop antimicrobial drugs to fight MDR bacterial infections.