Abstract
Introduction: Several medicinal plants, including Artemisia afra Jacq. Ex Willd, Lippia javanica (Burm.f.) Spreng, Tetradenia riparia (Hochst.) Codd, and Tulbaghia violacea Harv have been used in treating illnesses such as respiratory infections and their associated inflammatory dysregulation. The study aimed to evaluate the quantitative phytochemical content and the nitrite inhibition strength of the selected medicinal plant extracts.
Methods: A cold-maceration aqueous extraction procedure was employed for phytoconstituent extraction from dried plant material. The total phenolic content (TPC), along with total flavonoid content (TFC), total tannin content (TTC), and total saponin content (TSC), was quantitatively analyzed in the plant extracts. Cytotoxicity evaluation was done using the MTT assay to measure the minimum lethal concentrations against RAW 264.7 macrophage cell lines, and inhibition of nitrite production was assessed using a RAW macrophage cell-based assay.
Results: All plant extracts contained measurable levels of the tested phytochemicals, with A. afra roots showing the highest phenolic and flavonoid content at 48.54 ± 1.33 mg GAE (gallic acid equivalent)/g and 39.76 ± 1.56 mg QE (quercetin equivalents)/g, respectively. The extracts exhibited relatively low cytotoxicity against RAW macrophage cells, with LC50 values ranging between 64 ± 2.2 and 1443 ± 86.2 µg/mL. The most nitrite inhibition was observed in T. riparia leaf extracts, with 86% inhibition at 12.5 µg/mL. Correlation analysis further showed that extracts with higher phenolic content exhibited stronger nitrite inhibition properties.
Conclusion: Overall, all extracts demonstrated nitrite inhibition activity, showing the possible medicinal uses of these plants against respiratory infections with their associated inflammation.