Ethnobotanical survey and antibacterial screening of medicinal grasses in KwaZulu-Natal Province, South Africa

An ethnobotanical survey was undertaken from May 2015 to May 2016 to identify grasses used in traditional medicine in KwaZulu-Natal, South Africa. Indigenous knowledge was obtained from sixty traditional healers through questionnaires and face-to-face interviews. Thereafter, the different grass species were collected and identified at the herbarium at the University of KwaZulu-Natal, Pietermaritzburg, South Africa. Voucher specimens were also kept for preservation and future material reference. The survey revealed that 13 grass species are used for medicinal purposes; these grasses are mostly used as mixtures with other medicinal plants. The documented grass species are mostly used to cure skin diseases, body pains, urinary tract infections, teething troubles, body cleansing, skin diseases, bleeding and eye infections. In this study, the most commonly and frequently mentioned grass species were the Cymbopogon species which are used for skin disease and body cleansing. The 13 grass species identified were evaluated for antibacterial activity against six bacterial strains (Staphylococcus aureus, drug resistant S. aureus, drug resistant Klebsiella pneumoniae, multi-drug resistant Escherichia coli, Pseudomonas aeruginosa and Enterococcus faecalis). Coix lacryma-jobi root and leaf hexane extracts, Setaria megaphylla root dichloromethane extract and Cynodon dactylon whole plant hexane, dichloromethane and methanol extracts had the highest antibacterial activity (0.6 mg/ml) against S. aureus. Cymbopogon species root (dichloromethane) extract had moderate activity (1.3 mg/ml) against three bacterial strains (S. aureus, multi-drug-resistant E. coli and E. faecalis). Overall, these findings partially validate the use of grasses in South African traditional medicine and highlight their potential as remedies against bacterial-related infections.