The Department of Microbiology, Parasitology, and Biotechnology is delighted to announce to the scientific community and extend its congratulations to Dr. Abdel-razakh Hissein Hassan (Third from the right in the picture), on the successful defense of his PhD on 11th December 2024 at Sokoine University of Agriculture (SUA). His PhD thesis is titled “In vitro studies of the antimicrobial and antioxidant properties of Chadian medicinal plants.”
Dr. Abdel-razakh Hissein Hassan began his PhD program at the Department of Microbiology, Parasitology, and Biotechnology within the College of Veterinary Medicine and Biomedical Sciences (CVMBS) in October 2020. He was guided and supervised by Dr. Abubakar Shaaban Hoza (SUA), Prof Gaymary George Bakari (SUA), and Prof. Pan Cheol-Ho of the Korea Institute of Science and Technology (KIST).
List of members of the panel for the viva voce examination
| 1 | Chairperson | Prof. Philemon Wambura |
| 2 | Appointee of the Principal, CVMBS | Dr. Julius John |
| 3 | Appointee of the Head of Department | Dr. Alexanda Mzula |
| 4 | Independent Internal Examiner 1 who did not supervise | Prof. Claudius Luziga |
| 5 | Independent Internal Examiner 2 who did not supervise | Prof. Robert Max |
Summary of findings
This research investigated natural substances from Chadian medicinal plants to preserve medicinal resources and support traditional medicine. Bauhinia rufescens, Ocimum basilicum, and Salvadora persica were selected based on an ethnobotanical survey among Chadian healers in 2021. The study assessed their antimicrobial and antioxidant properties through literature reviews, phytochemical screening, and bioactivity assays. Antimicrobial tests against Escherichia coli, Klebsiella pneumoniae, Salmonella typhi, Enterococcus faecalis, Staphylococcus aureus, Shigella dysenteriae, and Candida albicans revealed significant activities. Phytochemical screening confirmed polyphenols, alkaloids, saponins, flavonoids, and terpenes/steroids in all plants. Fractionation using solvents of increasing polarity highlighted ethyl acetate fractions as the richest in phenolic and flavonoid contents, with strong antioxidant activity (low IC50 values in DPPH and ABTS assays). Isolation from ethyl acetate fractions yielded six compounds, including hydroxyphenylacetic acid, taxiphyllin, epicatechin, and rutin from B. rufescens, and rosmarinic acid and nepetoidin B from O. basilicum. Hydroxyphenylacetic acid, taxiphyllin, and epicatechin are reported here for the first time as natural products in B. rufescens. Rosmarinic acid and rutin exhibited the highest antibacterial and antioxidant activities, with low MICs/MBCs (0.62 µg/mL) and IC50 values (<0.6 µg/mL). Cytotoxicity assays confirmed low toxicity against C2C12 cells. These findings validate the traditional use of these plants for treating infectious and oxidative stress-related diseases and highlight their potential as sources of novel bioactive compounds.
Publications:
- Abdel-razakh Hissein Hassan, Gaymary George Bakari, Cheol-Ho Pan, Abubakar Shaaban Hoza. (2023). In vitro studies of the antimicrobial properties and qualitative phytochemical analysis of selected Chadian medicinal plants. Journal of Applied Biological Chemistry 2024;67. FULL TEXT
- Abdel-razakh, H. H., Gaymary, G. B., Pan, C. & Hoza, A. S. (2024). In vitro studies of the antimicrobial properties and qualitative phytochemical analysis of selected Chadian medicinal plants. Journal of Applied Biological Chemistry 67:131−140. FULL TEXT
- Abdel-razakh, H. H., Gaymary, G. B., Pan, C., Park J.& Hoza, A. S. (2024). Phenolic contents and antioxidant properties of Bauhinia rufescens, Ocimum basilicum and Salvadora persica used as medicinal plants in Chad Molecules 2024, 29(19), 4684; FULL TEXT
- Abdel-razakh, H. H., Gaymary, G. B., Pan, C., Park J.& Hoza, A. S. (2024). Antibacterial, antioxidant and cytotoxicity potentials of secondary metabolites isolated from Bauhinia rufescens and Ocimum basilicum ethyl acetate fractions. Molecules (submitted).