Antimicrobial and cytotoxic effects of medicinal plants traditionally used for the treatment of sexually transmitted diseases

Abstract

Sexually transmitted diseases (STDs) are a major problem internationally, with approximately one million new infections recorded daily. Antibiotic resistance of STD pathogens is a cause for concern hence there is a need to develop new drugs for the treatment of STDs. There has thus been an increased interest in evaluating medicinal plants as a potential source for the discovery of new drugs. This study aimed to evaluate the antimicrobial activity of nine ethanolic plant extracts, selected on the basis of traditional usage, on four pathogens associated with STDs, to determine their antioxidant effects, to investigate their cytotoxic effects against two cancer cell lines associated with STDs and one non-tumorigenic cell line, and to evaluate potential cytotoxicity. The antimicrobial activity of the extracts was evaluated against three STD pathogens: Neisseria gonorrhoeae, Candida albicans and Gardnerella vaginalis using the microdilution method. Furthermore, the disk diffusion method was used to test selected extracts on Malassezia furfur. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) and nitric oxide (NO) radical scavenging activity of the extracts was further investigated as the pathogens used in the study cause persistent inflammation. Additionally, the cytotoxic properties of the extracts were evaluated against human squamous cell carcinoma (A431), human keratinocytes (HaCat) and human cervical adenocarcinoma (HeLa) cell lines. The root extract of Rhoicissus tridentata showed the highest antimicrobial activity against C. albicans and N. gonorrhoeae with minimal inhibitory concentrations (MICs) of 0.78 and 0.39 mg/mL, respectively. The R. tridentata extract furthermore, displayed the most noteworthy antifungal activity against M. furfur with a 20.3 ± 4.7 mm zone of inhibition at 2 mg/mL and showed significant DPPH radical scavenging activity (IC50 = 2.3 ± 1.9 µg/mL). Moreover, the R. tridentata extract showed moderate cytotoxicity against HaCat cells and low to no toxicity against A431 and HeLa cells with IC50 values of 121.3 ± 6.0, 110 ± 7.1 and 202.3 ± 7.0 µg/mL, respectively. The findings of the study revealed that R. tridentata is a candidate for further evaluation for the management of STDs through its significant antimicrobial and antioxidant activity. The study is the first to report the cytotoxic effects of R. tridentata on selected cell lines as well as the NO scavenging effects and the antimicrobial activity against M. furfur.