Peter K. Cheplogoi

An azole, an amide and a limonoid from Vepris uguenensis (Rutaceae)

The limonoid derivative, methyl uguenenoate, the azole, uguenenazole, and the amide, uguenenonamide, together with the known furoquinoline alkaloids flindersiamine and maculosidine, and syringaldehyde have been isolated from the root of the East African Rutaceae Vepris uguenensis. While methyl uguenenoate and the furoquinoline alkaloids displayed mild antimalarial activity, the azole and amide were completely inactive.

Molecular modeling of major tobacco alkaloids in mainstream cigarette smoke

BackgroundConsensus of opinion in literature regarding tobacco research has shown that cigarette smoke can cause irreparable damage to the genetic material, cell injury, and general respiratory landscape. The alkaloid family of tobacco has been implicated is a series of ailments including addiction, mental illnesses, psychological disorders, and cancer. Accordingly, this contribution describes the mechanistic degradation of major tobacco alkaloids including the widely studied nicotine and two other alkaloids which have received little attention in literature. The principal focus is to understand their energetics, their environmental fate, and the formation of intermediates considered harmful to tobacco consumers.MethodThe intermediate components believed to originate from tobacco alkaloids in mainstream cigarette smoke were determined using as gas-chromatography hyphenated to a mass spectrometer fitted with a mass selective detector (MSD) while the energetics of intermediates were conducted using the density functional theory framework (DFT/B3LYP) using the 6-31G basis set.ResultsThe density functional theory calculations conducted using B3LYP correlation function established that the scission of the phenyl C–C bond in nicotine and β-nicotyrine, and C–N phenyl bond in 3,5-dimethyl-1-phenylpyrazole were respectively 87.40, 118.24 and 121.38 kcal/mol. The major by-products from the thermal degradation of nicotine, β-nicotyrine and 3,5-dimethyl-1-phenylpyrazole during cigarette smoking are predicted theoretically to be pyridine, 3-methylpyridine, toluene, and benzene. This was found to be consistent with experimental data presented in this work.ConclusionClearly, the value of the bond dissociation energy was found to be dependent on the π–π interactions which plays a primary role in stabilizing the phenyl C–C in nicotine and β-nicotyrine and the phenyl C–N linkages in 3,5-dimethyl-1-phenylpyrazole. This investigation has elucidated the energetics for the formation of free radicals and intermediates considered detrimental to human health in cigarette smoking.Graphical abstractSome molecular alkaloids of tobacco the plant

Larvicidal activity of extracellular secondary metabolites from a Stereum species Hill ex Pers. (JO5289) against the dengue fever mosquito, Aedes aegypti (Linn) (Diptera: Culicidae)

The main objective of this investigation was to find mosquito larvicidal secondary metabolites from a basidiomycete – Stereum species (JO5289) – against Aedes aegypti . The Stereum species (JO5289) was collected in July 2005 from undisturbed habitat in Londiani forest in Rift Valley province, Kenya. Extracellular crude extracts from Stereum species (JO5289) produced strong activity against A. aegypti larvae. Purification of the crude extracts targeting larvicidal activity using chromatography gave three active compounds namely; tyrosol, 3-methoxy-5-methyl-1,2-benzenediol and 2-hydroxy-4-(4-hydroxychroman- 7yl) but-3-enal. The chemical structures of the compounds were determined using the nuclear magnetic resonance (NMR) spectral data and comparison with literature values. When tested for larvicidal activity, the LC 50 for the three compounds were 26.7, 17.3 and 14.5 ppm, respectively, while LC 90 were 85.3, 83.5 and 82.9 ppm, respectively, after 24 h of exposure. These compounds have been produced from cultures of a Stereum species and reported to have mosquito larvicidal activity for the first time. Key words: Basidiomycete, Stereum species, Aedes aegypti , extracellular metabolites and larvicidal.

Chemical Constituents in Extracts from Leaves of Lantana trifolia and Their In Vitro Anti-oxidative Activity

Abstract Objective To isolate, purify, and analyze the anti-oxidants from the leaves of Lantana trifolia . Methods The anti-oxidative activities of the crude extracts from liquid-liquid extraction of L. trifolia leaves were assayed by 1,1-diphenyl-2-picrylhydrazyl (DPPH) method to assess their radical scavenging and reducing abilities. The total flavonoids and phenol contents in the ethyl acetate fraction were determined by colorimetric and Folin-Ciocalteu methods, respectively. Chemical constituents were isolated from the ethyl acetate fraction and repeatedly purified using silica gel, Sephadex LH-20 column chromatography, and HPLC, respectively. The chemical structures isolated were identified by spectral analysis and chemical evidence. Results Ethyl acetate partition from liquid-liquid extraction exhibited the highest anti-oxidative activity with an IC 50 value of 4.94 μg/mL, close to that of the standard (vitamin C, VC, 4.23 μg/mL). The extract was proved to contain total flavonoids and phenol contents with values of (39.0 ± 1.6) and (29.27 ± 1.46) mg/g, respectively. Six compounds were isolated and identified as kaempferol-3,7-dimethyl ether ( 1 ), verbascoside ( 2 ), apigenin ( 3 ), umuhengerin ( 4 ), ladanetin ( 5 ), and scutellarein-7- O -β- D -apiofuranoside ( 6 ). Conclusion The ethyl acetate extract from the leaves of L. trifolia possesses the potent anti-oxidative and free radical scavenging activities which are directly proportional to the concentration of phenolic contents. The anti-oxidative activity of the extract from the leaves of L. trifolia is due to its proton donating ability that converts free radicals to more stable products and terminates chain reactions. Compound 1 is isolated from the plants of Lantana Linn. for the first time. The mechanisms may be related to the therapeutic benefits of the certain traditional claims of wild L. trifolia .

In vitro inhibition of tomato Fusarium wilt causative agent by zearalenone from a soil inhabiting fungus

To find naturally occurring compounds for the control of Fusarium wilt disease of tomato in the farming fields, 200 fungal strains were cultured in liquid media and screened for antifungal activity against Fusarium oxysporium f. sp. Lycosperci . The screening was carried out using in vitro antifungal assays and coincidentally a strain of Fusarium species was found to produce secondary metabolites, which were prepared as crude extracts that showed strong antifungal activity. The responsible compound was purified using column chromatography and the chemical structure of the purified compound was determined using nuclear magnetic resonance (NMR) spectroscopic techniques. A known compound, zearalenone, was found to be responsible for the antifungal activity, with a minimum inhibitory concentration (MIC) of 550 ± 10.5 ppm. This is a sufficient inhibition for F. oxysporium f. sp. Lycosperci , which is the causative agent for Fusarium wilt disease to tomato. Given the global abundance of zearalenone and its implication to human health, the results from this study suggest a sustainable manner of disposing of the mycotoxin and simultaneous benefit in control of the Fusarium wilt disease. It is recommended from this finding that it can be used to suppress fungal attack onto the roots of tomato plant to manage the Fusarium wilt disease. Keywords: Fusarium oxysporium f. sp. Lycosperci , tomato, submerged cultures, column chromatography, zearalenone

Determination of major tobacco alkaloids in mainstream cigarette smoking

The popularity of tobacco use worldwide has kicked off one of the greatest clinical debates on human toxicology and public health in general. Accordingly, this study investigates some of the alkaloids in tobacco believed not only to be addictive and carcinogenic but also as precursors for other related medical problems. The characteristic behaviour, identification and product evolution of β-nicotyrine and 3, 5-dimethyl-1-phenylpyrazole in tobacco is reported extensively in this study for the first time. Two commercial cigarette brands coded SM1 and ES1 were explored for evolution of major alkaloids over a modest temperature range of 200–700° C for a total pyrolysis time of 3 minutes using a tubular quartz reactor, typically in increments of 100°C using nitrogen as the pyrolysis gas at a residence time of 2.0 seconds under 1 atmosphere pressure. The heating rate of the heater was ∼ 20°C s−1. The pyrolysate was passed over 10 mL analytical grade methanol and analyzed using a Gas-Chromatography hyphenated to a mass spectrometer (GC-MS) with a mass selective detector (MSD). GC-MS results showed that nicotine was the major alkaloid in both cigarettes reaching a maximum at ∼ 400°C (8.0 x 108 GC-Area counts) for ES1 cigarette and 500°C (∼2.7 x 108 GC-Area counts for SM1 cigarette. Clearly, the ratio of nicotine for ES1 to SM1 is approximately 3 indicating that ES1 cigarette is rich in nicotine. Based on this data alone, ES1 cigarette was found to be more addictive.