ABSTRACT
Respiratory tract infections (RTIs) are frequent ailments among humans and are a high burden on public health. This study aimed to determine the in vitro antibacterial, anti-inflammatory, and cytotoxic effects of indigenous medicinal plants used in the treatment of RTIs, namely, Senna petersiana, Gardenia volkensii, Acacia senegal, and Clerodendrum glabrum. Dried leaves were extracted using various organic solvents. Antibacterial activity was quantified using the microbroth dilution assay. Protein denaturation assays were used to evaluate anti-inflammatory activity. The cytotoxicity of the extracts towards THP-1 macrophages was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Antioxidant activity was determined using free radical scavenging activity and ferric-reducing power. Total polyphenolics were quantified. Liquid chromatography mass spectrometry was used to evaluate the acetone plant extracts. Nonpolar extracts had noteworthy antibacterial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Mycobacterium smegmatis where MIC values ranged between 0.16 and 0.63 mg/mL. At 100 µg/mL, A. senegal, G. volkensii, and S. petersiana had a nonsignificant effect on the viability of the THP-1 macrophages. The LC-MS analysis of the leaf extracts of S. petersiana detected Columnidin, Hercynine, L-Lysine citrate, and Gamma-Linolenate. A pentacyclic triterpenoid, cochalate, was detected in G. volkensii. Two flavonoids 7-hydroxy-2-(4-methoxyphenyl)-4-oxo-chroman-5-olate and (3R)-3-(2,4-dimethoxyphenyl)-7-hydroxy-4-oxo-chroman-5-olate were detected in the C. glabrum extract. The findings from this study indicated that the leaves of the selected plant extracts possess antioxidant, anti-inflammatory, and antibacterial activity. Therefore, they may serve as good candidates for further pharmaceutical investigations.
