Phytochemical Constituents, Antioxidant, Cytotoxicity, Antimicrobial, Antitrypanosomal, and Antimalarial Potentials of the Crude Extracts of <i>Callistemon citrinus</i>

Plants are reservoir for potentially useful bioactive compounds, and owing to the rising occurrences of drug resistance to malaria parasites, there is a need to discover and develop new phytochemicals in plant that can be used as antimalarial agents. In this study, we gave a detailed description of the phytochemicals present in both ethyl acetate and methanolic extracts of <i>Callistemon citrinus</i> (<i>C. citrinus</i>) using Gas Chromatography-Mass Spectrometry (GC-MS) analysis; both extracts were also evaluated for their <i>in vitro</i> antimalarial, antitrypanosomal, and cytotoxicity activities against <i>Trypanosoma brucei brucei</i> (<i>T. b brucei</i>) parasites, <i>Plasmodium falciparum</i> (<i>P. falciparum</i>) malaria parasites 3D7 strain, and human cervix adenocarcinoma cells (HeLa cells); in addition, the antimicrobial and antioxidant efficacies were determined using standard methods. Both extracts were characterized by a high amount of fatty acids (52.88 and 62.48%). The ethyl acetate extract exhibited a greater activity with minimum inhibitory concentration (MIC) values ranging from 0.025 to 0.10 mg/mL while the methanol extract ranged from 0.025 to 0.15 mg/mL. Both extracts were bactericidal to <i>Escherichia coli ATCC 35150</i> (<i>E. coli</i>) and <i>Pseudomonas aeruginosa ACC</i> (<i>P. aeruginosa</i>). Qualitative and quantitative phytochemical screenings conducted for both extracts revealed the presence of alkaloids, glycosides, saponins, steroids, and triterpenoids, fat and oils, flavonoids, phenols, and tannins in varying amounts. Both crude extracts exhibited antitrypanosomal potentials with an IC₅₀ of 6.6/9.7 <i>μ</i>g/mL and antiplasmodial activities with an IC₅₀ of 8.4/13.0 <i>μ</i>g/mL. Conclusion from this study indicates that apart from the folkloric uses of this plant in traditional settings, the extracts possess a broad spectrum of antimicrobial, antitrypanosomal, and antimalarial activities and some pharmaceutically essential bioactive components with remarkable antioxidant capacities that may be used in the synthesis of novel drugs for the management of different varieties of ailments.