Evaluation of the antibacterial and antifungal potentials of peptide-rich extracts from selected Nigerian plants

Abstract

Introduction: Host defence peptides (HDPs) has gained wide recognition as a potential source of antimicrobial agents because of their abundance in nature, low incidence of reported resistance, and their immunomodulatory properties. This study investigated the presence and antimicrobial activities of bioactive peptides in seven selected plants from the Rubiaceae, Apocynaceae, and Euphorbiaceae families. Methods: The reversed-phase solid-phase extraction was used to obtain the peptide-rich fractions from the crude extracts of the plants, and the circular peptides were chemically detected by a modified G-250 spray on a developed TLC plate. The peptide fraction and crude extracts were screened for their antimicrobial activities using the broth microdilution method. The rate of kill study was conducted for the peptide fractions Euphorbia hirta and Nauclea diderichii Results: The study revealed Nauclea diderichii peptide-rich fraction as the most potent on the tested strains of gram-positive and gram-negative bacteria and fungi (MIC = 7.8, 15.63-62.5, and 7.8 μg/mL respectively). Euphorbia hirta and Nauclea diderichii peptide fractions exhibited bactericidal activity (MIC index ≤4, and >3Log 10 reduction of initial inoculum) and have a broad spectrum of activity, which further validates their ethnomedicinal use in the management of diverse infectious diseases, including enteric and respiratory tract infections. The peptide fractions of all the plants are more potent than the crude extracts. Conclusion: This study established the antimicrobial potentials of the peptide-rich fractions from these plant species, and the basis for further investigation to isolate and characterize the bioactive peptides responsible for their antimicrobial activities.