GC-MS Analysis, Antibacterial, and Anticancer Activities of Hibiscus sabdariffa L. Methanolic Extract: In Vitro and In Silico Studies

Abstract

The emergence of bacteria that are resistant to several antibiotics has represented a serious hazard to human health globally. Bioactive metabolites from medicinal plants have a wide spectrum of therapeutic possibilities against resistant bacteria. Therefore, this study was performed to investigate the antibacterial efficacy of various extracts of three medicinal plants as <i>Salvia officinalis</i> L., <i>Ziziphus spina-christi</i> L., and <i>Hibiscus sabdariffa</i> L. against pathogenic Gram-negative <i>Enterobacter cloacae</i> (ATCC13047), <i>Pseudomonas aeruginosa</i> (RCMB008001), <i>Escherichia coli</i> (RCMB004001), and Gram-positive <i>Staphylococcus aureus</i> (ATCC 25923), bacteria using the agar-well diffusion method. Results revealed that, out of the three examined plant extracts, the methanol extract of <i>H. sabdariffa</i> L. was the most effective against all tested bacteria. The highest growth inhibition (39.6 ± 0.20 mm) was recorded against <i>E. coli</i>. Additionally, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of the methanol extract of <i>H. sabdariffa</i> were detected in the case of all tested bacteria. Moreover, an antibiotic susceptibility test revealed that all tested bacteria showed multidrug resistance (MDR). While 50% of tested bacteria were sensitive and 50% were intermediately sensitive to piperacillin/tazobactam (TZP) based on the inhibition zone but still less than the extract. Synergistic assay demonstrated the promising role of using a combination of <i>H. sabdariffa</i> L. and (TZP) against tested bacteria. A surface investigation using a scanning electron microscope of the <i>E. coli</i> treated with TZP, extract, or a combination of the two revealed extremely considerable bacterial cell death. In addition, <i>H. sabdariffa</i> L. has a promising anticancer role versus Caco-2 cells with IC₅₀ of 17.51 ± 0.07 µg/mL and minimal cytotoxicity upon testing versus Vero cells with CC₅₀ of 165.24 ± 0.89 µg/mL. Flow cytometric analysis confirmed that <i>H. sabdariffa</i> extract significantly increased the apoptotic rate of Caco-2-treated cells compared to the untreated group. Furthermore, GC-MS analysis confirmed the existence of various bioactive components in the methanol <i>hibiscus</i> extract. Utilizing molecular docking with the MOE-Dock tool, binding interactions between n-Hexadecanoic acid, hexadecanoic acid-methyl ester, and oleic acid, 3-hydroxypropyl ester were evaluated against the target crystal structures of <i>E. coli</i> (MenB) (PDB ID:3T88) and the structure of cyclophilin of a colon cancer cell line (PDB ID: 2HQ6). The observed results provide insight into how molecular modeling methods might inhibit the tested substances, which may have applications in the treatment of <i>E. coli</i> and colon cancer. Thus, <i>H. sabdariffa</i> methanol extract is a promising candidate to be further investigated for developing alternative natural therapies for infection treatment.