Phytochemical Analysis and Biological Activities of Secondary Metabolites Derived from Selected Ethiopian Medicinal Plants: An Integrated Computational and Experimental Study

Abstract

Plants synthesize a wide range of biologically active secondary metabolites, which serve for therapeutic agents against various human and animal diseases. Ethiopian traditional medicine has long harnessed the therapeutic properties of medicinal plants, including their potential to address various infectious diseases and cancer. By integrating modern scientific techniques with traditional knowledge, there is great potential to discover and develop new medicinal agents from Ethiopia's rich botanical heritage, thereby preserving both cultural wisdom and biodiversity. In this study, five plants were selected based on their ethnobotanical uses, reflecting their traditional significance. Silica gel column chromatographic separation of roots extracts of W. uniflora, T. vogelii, A. schimperi, R. glutinosa, and C. spinarum yielded four (97-99), seven (97, 100-105), five (106-110), eight (97,111-115), and two (116, 117) compounds, respectively. The structure of the isolated compounds was characterized using spectroscopic (IR, 1H and 13C (1D and 2D) NMR data and literature reports. GC-MS analysis of essential oils revealed that dibutyl phthalate (28.66%), cis nerolidol (41.7%), and cedrol (25.85%) as major constituents in the roots of W. uniflora, T. vogelii, and A. schimperi, respectively. Meanwhile, 4-hydroxy acetophenone was the principal component of the roots of R. glutinosa and C. spinarum, with percentages of 72.19% and 74.85%, respectively. The antibacterial activity of crude extracts and isolated compounds was evaluated using disc diffusion and broth micro dilution methods. DCM/MeOH (1:1) extracts of A. schimperi, and R. glutinosa, exhibited maximum inhibition of S. aureus with ZI of 15.6 ±0.47, and 17.3 ±0.81, respectively, compared to ciprofloxacin (31.0±0.0 mm). MeOH extract of R. glutinosa showed the highest antibacterial activity against S. aureus with ZI of 18.0±0.0 mm, compared to ciprofloxacin (31.0±0.0 mm, at 0.5mg/mL). DCM/MeOH (1:1) and MeOH extracts of C. spinarum also showed promising activity against S. pyogenes with ZI of 18.6±0.57 and 18.3±0.81mm, respectively, compared to ciprofloxacin (30.0±0.0 mm at 0.5mg/mL). DCM/MeOH (1:1) and MeOH extracts of T. vogelii demonstrated maximum activity against P. aeruginosa with MIC values of 0.5±0.0 and 0.66±0.2 mg/mL, respectively, compared to ciprofloxacin (0.078±0.0 µg/mL). Maackian (103) showed maximum antibacterial activity against P. mirabilis and P. aeruginosa with MIC values of 0.5±0.0 and 0.83±0.0 mg/mL, respectively, compared to ciprofloxacin (0.312 and 0.078µg/mL). Lupeol (107) and methyl gallate (114) showed maximum inhibition of S. aureus with ZI of 17.3±0.81 and 18.6±0.57mm, respectively, compared to ciprofloxacin (31.0±0.0 mm). EO extracts from W. uniflora and A. schimperi exhibited maximum inhibition of S. aureus (ZI of 17.6±0.47) and E.coli (ZI of 17.3±0.81mm). DCM/MeOH (1:1) and MeOH extracts of the roots of W. uniflora, T. vogelii, A. schimperi, R. glutinosa, and C. spinarum demonstrated promising DPPH radical scavenging with IC50 values ranging from 12.58 to 44.0 µg/mL, compared to ascorbic acid (5.83µg/mL). Compounds 98, 99, 102, 103, 105, 108, 114, and 115 displayed strong DPPH radical scavenging with IC50 values of 6.48, 9.48, 10.43, 10.73, 10.97, 10.66, 7.48, and 6.07 µg/mL, respectively, compared to ascorbic acid (5.83 µg/mL). DCM/MeOH(1:1) and MeOH extracts of A. schimperi showed antiviral activity against MDCK cells of anti-influenza A and B with IC50 values of 2 and 25.1 µg/mL, respectively. The docking analysis results revealed that compounds 101, 103, and 104, showed strong binding affinity towards PDB ID: 2UV0, PDB ID: 6F86, and PDB ID: 3T07 targets with binding energies of -7.6, -6.6 and -6.8 kcal/mol respectively, compared to ciprofloxacin with respective binding energies of -7.3, -7.4, and -7.2 kcal/mol. Compounds 101, 102, and 115 also showed strong binding interaction towards PDB ID: 4M8I, PDB ID: 1E9Y and PDB ID 6UKD receptors with respective binding energies of - 7.9, -7.0 and 5.7 kcal/mol compared to ciprofloxacin (ranging -6.8 to -8.8 kcal/mol). Towards PDB ID: 1DNU receptor, compounds 96, 98, 99, 102, 104, 105, 108, 114, 115, 116, and 117 exhibited promising binding free energies from -4.8 to -10.0 kcal/mol, compared to ascorbic acid (-5.7 kcal/mol). Towards topoisomerase IIα (PDB ID 4FM9) receptor, compounds 97, 98 and 103 displayed the lowest minimum binding energies of -9.1, -9.8, -9.2 kcal/mol respectively compared to vosaroxin (-7.8 kcal/mol). Compounds 97, 101, 102, 103, 104, 105, 107, 108, 114, 115, 116, and 117 obeyed Lipinski's rule of five with no violations. The proTox II screening analysis results revealed that all compounds under investigation were found to be non hepatoxicity, carcinogenin, mutagenic, and cytotoxic. Given the important antimicrobial and antioxidant activities demonstrated by plant extracts and isolated compounds, further research should focus on the development of these extracts into therapeutic agents. Future studies should include detailed safety evaluations, in vivo studies, and clinical trials to confirm efficacy and safety for potential therapeutic applications. Additionally, exploring the mechanism of action and optimizing extraction methods could enhance the yield and effectiveness of these plant based antimicrobial, antioxidant, and antiviral agents.