Alphonse W. WafulaRam ManoharAgola, Faith Caroline2023-03-032023-03-032022-10http://ir-library.ku.ac.ke/handle/123456789/24856A thesis submitted in partial fulfilment of the requirements for the award of the degree of Master of Science in chemistry in the school of pure and applied sciences, Kenyatta University . October 2022Malaria is one of the most common and severe tropical diseases on the planet, transmitted by the Anopheles gambiae mosquito. Malaria affects more than 300 million people each year, according to the World Health Organization. Each year, these diseases are estimated to kill between 1.5 and 3 million people worldwide, with nearly 90 percent of all illnesses affecting pregnant women and children under the age of five. Chemotherapy, vaccine development, and vector control are currently used to prevent and control malaria. Vector management has been hailed as a critical tool in the fight against malaria transmission in light of the plasmodium species' increasing resistance to currently available antimalarial medications. Controlling mosquitoes during their larval stage is an additional effort made by humanity in an attempt to combat malaria. The use of natural compounds derived from plants to control the insect pests is a non-toxic and environmentally friendly strategy. Research has shown that compounds from the Vebenaceae family have been identified and shown to have larvicidal activity. The phytochemical and mosquito larvicidal properties of crude extracts and fractions derived from Stacytarpheta urticifolia, a member of the Vebenaceae family, were investigated in this work. The dry powdered stems of S. urticifolia were extracted using hexane, DCM, EtOAc and methanol for a total of 48 hours, with each extraction utilizing a different solvent. Phytochemical screening showed presence of terpenoids, alkaloids, tannins, steroids and flavonoids in the plant. For bioassay investigations, different concentrations of extracts were used. The larvicidal activity of the polar crude extracts was much greater than that of the non-polar extracts; MeOH LC50=0.08, Hexane LC50=10.59. The cytotoxicity tests also revealed that the EtOAc and methanol extracts were the more toxic to brine shrimp eggs; MeOH LC50= 6.48x10-8, EtOAc LC50=0.0015. Column chromatography and repeated PTLC on the bioactive crude extracts from Hexane, DCM, EtOAc and MeOH gave a white amorphous solid (EtOAc:MeOH, 7:3). Upon use of 1H NMR, 13C NMR, DEPT, HMBC and HSQC led to SUS 1 an oleanane tritepene, 1,2,3,4,4a,5,6a,7,8a,9,10,11,12,12a,13,13a,14,14a,14b-icosahydro-2,3,11,12,13apentahydroxy-4,4,6a,12,14b-pentamethyl-10-oxobenzo[α]tetracene-12a-carboxilic acid. A white amorphous solid (EtOAc:MeOH, 7:3). Another oleanane tritepenoid with a sugar moiety, 8a-acetyloctadecahydro-6b,8,12-tihydroxy-4,4,6a,11,12b,14b-hexamethyl-2(tetrahydroxo-3, 4, 5trihydroxy-6- (hydroxymethyl) - 2H- pyran - 2-yl oxy) picen - 6 (6aH, 6bH ,14Bh)-one, SUS 3 was also obtained as white crystalline solid (EtOAc:MeOH, 7:3). In addition, two common plant sterols were also isolated from Chloroform: EtOAc (1:1); 3β-stigmasterol, SUS 2 as white powder and 3β-sitosterol, SUS 4 as colourless needlike crystals. The results from this study provides a basis for further research in malaria control.enPhytochemicalmosquito larvicidalstachytarpheta urticifoliaThesis