Antibacterial, Antioxidant, and Safety-Related Cytotoxic Properties of Compounds Isolated from Bauhinia rufescens and Ocimum basilicum

Abstract

Background Bauhinia rufescens (B. rufescens) and Ocimum basilicum (O. basilicum) are widely used in African traditional medicine for treating infectious and oxidative stress–related conditions. However, the specific phytochemicals responsible for these effects and their safety profiles remain insufficiently characterized. This study addresses this gap by isolating, identifying, and biologically evaluating individual bioactive compounds from both plants. Objective To isolate, characterize, and evaluate the antibacterial, antioxidant, and safety-related cytotoxicity profiles of purified compounds obtained from B. rufescens and O. basilicum. In addition, this study establishes novelty by reporting several compounds for the first time in B. rufescens. Methods Ethyl acetate fractions were purified using High-Performance Liquid Chromatography (HPLC), and compound structures were elucidated by Proton Nuclear Magnetic Resonance (1H-NMR) and Mass Spectrometry (MS). Antibacterial activity was evaluated by the broth microdilution method against Escherichia coli (E. coli) (KCTC 2593), Staphylococcus aureus (S. aureus) (KCTC 1916), and Salmonella typhi (S. typhi) (ATCC 14028). Antioxidant activity was assessed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging assays, while cell viability was determined via the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay on C2C12 myoblast cells to ensure accurate assessment of safety. Results Six compounds were isolated: epicatechin, hydroxyphenylacetic acid, nepetoidin B, rosmarinic acid, rutin and taxiphyllin. Epicatechin, hydroxyphenylacetic acid, and taxiphyllin were identified in B. rufescens for the first time, expanding its known phytochemical profile. Rosmarinic acid and rutin exhibited the strongest antibacterial activity, with Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values of 0.62 µg/mL against all tested strains. These two compounds also demonstrated the highest antioxidant capacity, displaying the lowest half-maximal inhibitory concentration (IC₅₀) values in both radical scavenging assays. Cytotoxicity testing indicated that all isolated compounds displayed only moderate, dose-dependent reductions in cell viability, with IC₅₀ values ranging from 6.82 ± 0.05 µg/mL to 18.71 ± 0.00 µg/mL, supporting their preliminary safety for potential therapeutic applications. Conclusion The isolated compounds from B. rufescens and O. basilicum exhibit notable antibacterial and antioxidant activities coupled with favorable safety-related cytotoxicity profiles. The first-time identification of three compounds in B. rufescens underscores its chemical novelty and therapeutic potential. These findings justify further pharmacological and mechanistic investigations.