http://localhost:8080/xmlui/handle/123456789/44 2026-08-12T15:45:58Z 2026-08-12T15:45:58Z Osunga, Salome Achola http://localhost:8080/xmlui/handle/123456789/8318 2025-02-28T08:52:45Z 2023-01-01T00:00:00Z

Characterization Of Phytochemicals From Chamaecrista Nigricans Vahl And Ximenia Americana L With Antimicrobial Activities Osunga, Salome Achola Infectious diseases account for most deaths globally, far beyond the damage incurred by warfare and food shortages. 10 million deaths have resulted from infectious diseases worldwide; lower respiratory tract infections are the largest, followed by diarrhoea, tuberculosis, HIV-AIDS, and Malaria. 70,000 deaths have resulted due to the increased drug resistance in malaria, antibacterial, and antifungal drugs. Bioactive compounds are continually being explored for the prophylaxis and treatment of these infectious diseases and also to manage drug resistance limitations acquired by some of the currently used drugs. This study aimed to characterize phytochemicals from the Chamaecrista nigricans plant and the Ximenia americana roots with antiplasmodial and antimicrobial activities. The grounded plant of C. nigricans and X. americana roots were extracted via cold extraction using a 1:1 methanol: DCM solvent volume ratio. Fractionation and purification were done using the silica column chromatography technique, and Sephadex LH20 was used to purify some compounds further. Chemical structures were identified using FTIR, GC-MS, and NMR spectroscopic techniques. C. nigricans yielded previously reported compounds compounds: chrysophanol (1,8-dihydroxy-3-methylanthraquinone) (SAO-04), (1,6,8-trihydroxy-3-methylanthraquinone) (SAO-05), and physcion (1,8-dihydroxy-3- methyl-6-methoxyanthraquinone) (SAO-06). X. americana yielded seven compounds: Octahydro-3-isopropyl-4a,5-dimethylnaphthalen-2 (1H)-one, Trans-2-dodecenedioic acid, Octadecanoic acid, 1,2-dihexadecanoylglycerol, Methyl-14-methylpentadecanoate, (Z)-7- tetradecenal and (Z)-9-hexadecenal. The crude extracts from the two plants had IC50 values of > 47.6 μg/ml against both P. falciparum D6 (chloroquine sensitive) and W2 (chloroquine-resistant). The compounds isolated from the two plants exhibited antiplasmodial activity with IC50 values of > 4.76 μg/ml against both P. falciparum D6 (chloroquine sensitive) and W2 (chloroquine-resistant). The crude extracts of the two plants displayed reduced toxicity with an IC50 value of > 47.6 μg/ml, while the compounds from the two plants were cytotoxic with IC50 values ranging between 3.8378-> 4.76 μg/ml against the normal VERO cells. Crude extract of X. americana had mild activity against Cryptococcus neoformans with IC50 value >200 μg/ml. Crude extract of C.nigricans had no activity against Cryptococcus neoformans, while compounds isolated from it exhibited activity with IC50 values ranging from 4.19-8.63 μg/ml. An alkaloid fraction (SAO-07) from X. americana portrayed potent activity against E. coli (IC50 value of 1.45 μg/ml) compared to the control drug Meropenem (IC50 value of 7.57μg/ml). Compounds isolated from C.nigricans had notable activity against methicillin-resistant Staphylococcus aureus with IC50 values ranging between 6.93-16.99 μg/ml in comparison to control drugs whose IC50 values ranged between 2.63-17.57 μg/ml. In conclusion, it was observed that compounds from C.nigricans have antimicrobial activity against methicillin-resistant S. aureus, while an alkaloid isolated from X. americana exhibited activity against E. coli. It was also established that both crude extracts of the two plants had minimal antiplasmodial activity and toxicity while their isolated compounds were cytotoxic. The findings also ascertain that these plants harbour antimicrobial and antiplasmodial compounds and should be further investigated for novel antimalarial and antimicrobial drugs.

2023-01-01T00:00:00Z AGORA, JARED OMARI http://localhost:8080/xmlui/handle/123456789/79 2024-02-08T07:13:35Z 2023-01-01T00:00:00Z

THEORETICAL CHARACTERIZATION OF THE STRUCTURAL, ELECTRONIC AND MECHANICAL PROPERTIES OF SUPERCONDUCTING GdBa2Cu3O7-x AGORA, JARED OMARI The aim of the study was to characteris the GdBa2Cu3O7-x perovskite superconductor with the view knowing the associated properties under different conditions of pressure. The study applied the computational methods to investigate the structural, electronic and mechanical, properties of the GdBa2Cu3O7-x perovskite superconductor and determined how its properties affect the mechanism of superconductivity. With the local the generalized gradient approximation in the frame work of density functional theory using the Quantum espresso code, the ground state properties and equation of state were obtained using the Plane waves. The phenomenon of phase transition studied through pressure induction. The effect of pressure on the band structure, density of states and the partial density of state were also assessed. The orbitals that are responsible for metallization and superconductivity were also computed at varied pressure. The effect holes doping with pressure was also simulated. The BCS theory and the Mc Millan’s equation were used to calculate its superconducting transition temperature at different pressure. Doping with variation of oxygen concentration was done. The phase transition was found to occur at 21.9 GPa. It was found that pressure results to narrowing of the band gap for this material and eventually the material undergoes metallization. The orbital that become predominant at the high superconductivity transition temperature below the pressure of phase transition were; Cu 1d and O 2p from the CuO in the valence band near the Fermi level and the Gd 5p near the Fermi level. The stability criterion was satisfied from the calculated elastic constants. Calculated elastic properties were used to calculate Debye temperature and the maximum value was achived at ~20GP. The underdoped regime, where the holes were smaller compared to the ones at optimum doping, was determined to be below 20 GPa of doping pressure. Optimal doping pressure where was achieved at ~ 20 GPa.. There was a drop in T_C above the pressure of around ~20 GPa, which was considered the overdoping regime. The highest calculated 𝑇𝐶 (max) was ~141.16 K at ~20GPa. With oxygen doping the 𝑇𝐶 (max) was found to be 137.9 K when the value of x was 0.65. the finding of the study can be used to in material design for application

2023-01-01T00:00:00Z