Phytochemical and ethnomedicinal evidences of the use of Alternanthera brasiliana (L.) Kuntze against infectious diseases

Ethnopharmacological relevance: Popularly known as "penicilina" and "terramicina", Alternanthera brasiliana (L.) Kuntze belongs to the Amaranthaceae family and stands out for its ethnomedicinal uses in the treatment of infections caused by pathogenic microorganisms in some countries. Aim of the study: The present study aimed to carry out a literature review and analyze whether the scientific evidence really validates the numerous indications for the use of A. brasiliana in traditional medicine for the treatment of infectious diseases. Phytochemical and toxicological studies related to this species were also analyzed. Material and methods: Scientific documents were retrieved from Google Scholar, PubMed (R), ScienceDirect (R), SciELO, SpringerLink (R), Scopus (R), and Web of ScienceTM databases. The literature was reviewed from the first report on the antimicrobial activity of A. brasiliana in 1994 until April 2024. Results: According to the scientific documents analyzed, it was observed that A. brasiliana is widely used as a natural antibiotic for the treatment of infectious diseases in Brazil, mainly in the states of Rio Grande do Sul, Mato Grosso, and Minas Gerais. Its ethnomedicinal uses have also been reported in other countries such as Colombia and India. The leaves (78%) of A. brasiliana are the main parts used in the preparation of herbal medicines by traditional communities. Several A. brasiliana extracts showed low activity when evaluated against pathogens, including gram-positive bacteria, gram-negative bacteria, parasitic protozoa, and fungi. Only two studies reported that extracts from this plant showed high activity against the herpes simplex virus, Mycobacterium smegmatis, and Candida albicans. Phytochemicals belonging to the classes of phenolic compounds and flavonoid (52%), saturated and unsaturated fatty acids (33%), steroids and phytosterols (8%), terpenoids (5%), and fatty alcohol esters (2%) were identified in A. brasiliana. Toxicity (in vivo) and cytotoxicity (in vitro) studies of polar and non-polar extracts obtained from A. brasiliana leaves indicated that this plant is biologically safe. Conclusion: Despite being widely used as a natural antibiotic by traditional communities, scientific investigations related to the antimicrobial potential of A. brasiliana extracts have indicated inactivity against several pathogens.