Browsing by Author "Mayeku, Philip Wafula"

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    Anti-Bacterialactivities And Phytochemical Screening Of Extracts Of Different Parts Of Thalictrum Rhynchocarpum
    (2013) Mayeku, Philip Wafula; Hassanali, Ahmed M.; Kiremire, Bernard T.; Odalo, Josiah O.; Hertweck, Christian
    Parts of the plant Thalictrum rhyncocarpum are used in herbal medicine in Kenya to treat various infections. The aim of this study was to evaluate in-vitro anti-bacteria activities and phytochemical profiles of solvent extracts of the leaves, stem bark and root of Thalictrum rhyncocarpum against Bacillus subtilis-6633, Staphylococcus aures-SG 511, Escherichia coli SG 458, Pseudomonus aeruginosa-K799/61 and Mycobacterium vaccae-10670. Anti-bacterial activity tests were carried out using disc diffusion assay and tube dilution technique, and phytochemical screening was carried out through Thin Layer Chromatography. The crude extracts showed antibacterial effects on M. vaccae, P. aeruginosa and B. subtilis. M. vaccae was most sensitive, particularly to the methanol root extract. Phytochemical screening of the extracts suggested the presence of glycosides and alkaloids in the stem bark and root extracts, and flavonoids and triterpenes in the leaf extracts. The study showed interesting levels of activities of solvent extracts of different parts of T. rhyncocarpum against some of the bacteria tested (M. vaccae, P. aeruginosa and B. subtilis). The results provide some scientific rationale for the traditional use of the plant in Kenya to treat different microbial infections.
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    Chemical composition and mosquito repellency of essential oil of Conyza newii propagated in different geographical locations of Kenya
    (John Wiley & Sons, 2014) Mayeku, Philip Wafula; Omollo, N. I.; Odalo, O. J.; Ahmed, Hassanali
    Previously, essential oil of Conyza newii (Asterale: Asteracea, Oliv. & Hiern) growing in the northern part of West Pokot (35◦E, 1◦N) of Kenya was shown to be highly repellent [RD50 =8.9×10−5 mg/cm2, 95% confidence interval (CL)] to Anopheles gambiae s.s. Fumigant toxicity of the oil to the mosquito was also demonstrated. The major constituents of the oil were found to be monoterpenoids, including (S )-(-)-perillyl alcohol, (S )-(-)-perillaldehyde, geraniol, (R)-(+)-limonene, trans-β-ocimene and 1,8-cineol. In this study, the chemical composition and repellency of essential oils of the plant seedlings collected from West Pokot (35◦E, 1◦N) and propagated in seven different geographical regions of Kenya [West Pokot (35◦E, 1◦N), Kilome (37◦E, 1◦S), Naivasha (36◦E, 0◦), Webuye (34◦E, 1◦N), Nyakach (34◦E, 0◦), Kericho (35◦E, 0◦) and Nairobi (36◦E, 1◦S)] were compared. There were significant variations (P <0.01, 95% CL) in the relative proportions of the six constituents and this was reflected in the repellency of the essential oils (P <0.01, 95% CL). Higher repellency of the oil was associated with greater proportions of (S )-(-) perillyl alcohol, (S )-(-)-perillaldehyde and geraniol, and lower repellency was associated with an increased proportion of (R)-(+)-limonene. The results suggest significant epigenetic (chemotypic) variations in the repellency and composition of C. newii essential oils growing in different regions of Kenya.
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    In vitro anti-cancer efficacy and phyto-chemical screening of solvent extracts of Kigelia africana (Lam.) Benth
    (Cell press, 2021-01-25) Nyaga, Justine M.; Mukavi, Justus Wambua; Mayeku, Philip Wafula; Kituyi, Sarah Naulikha
    Background and objectives: Kigelia africana is a medicinal plant growing naturally in many parts of Africa. In Kenya, a water concoction of the plant is used to treat breast and prostate cancers. Laboratory data on its anti-cancer activity and active principles is limited, hence no scientific rationale for its medicinal use. This study reports on in-vitro toxic activities of dichloromethane and methanol extracts of the plant against human breast cancer cells and phytochemical screening of the two extracts. Methodology: Plant extracts were obtained by sequential solvent extraction of dry plant material (stem bark) using analytical grade dichloromethane: methanol (1:1) and methanol (Sigma Aldrich). In-vitro anti-cancer activities of the extracts were determined using the suphorhodamine (SRB) assay against a human breast cancer cell line (HCC 1937). Preliminary Thin layer chromatography of plant extracts was done using POLYGRAM® SIL G/UV254 plates (Merck) to establish presence of different classes of secondary metabolites. Results: In-vitro cytotoxic activities of the two extracts were significantly different (P ¼ 0.05). The methanol extract exhibited higher activity (IC50 ¼ 26.02 μg/ml) compared to that of dichloromethane: methanol (1:1) (IC50 ¼ 55.01 μg/ml). Phyto-chemical screening of the two extracts revealed the presence of terpenoids, phenols, steroids and flavonoids. Conclusion: The high in-vitro anti-cancer activities of solvent extracts of Kigelia africana justify its use in traditional medicine to manage breast cancer. Phytochemical analysis of the extracts reveal similar profiles hence the differences in their anti-cancer activities can be attributed to quantitative variations of various classes of secondary metabolites.
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    In vitro anti-cancer efficacy and phyto-chemical screening of solvent extracts of Kigelia africana (Lam.) Benth
    (Heliyon, 2020) Mukavi, Justus Wambua; Mayeku, Philip Wafula; Nyaga, Justin M.; Kituyi, Sarah N.
    Background and objectives: Kigelia africana is a medicinal plant growing naturally in many parts of Africa. In Kenya, a water concoction of the plant is used to treat breast and prostate cancers. Laboratory data on its anti-cancer activity and active principles is limited, hence no scientific rationale for its medicinal use. This study reports on in-vitro toxic activities of dichloromethane and methanol extracts of the plant against human breast cancer cells and phytochemical screening of the two extracts. Methodology: Plant extracts were obtained by sequential solvent extraction of dry plant material (stem bark) using analytical grade dichloromethane: methanol (1:1) and methanol (Sigma Aldrich). In-vitro anti-cancer activities of the extracts were determined using the suphorhodamine (SRB) assay against a human breast cancer cell line (HCC 1937). Preliminary Thin layer chromatography of plant extracts was done using POLYGRAM® SIL G/UV254 plates (Merck) to establish presence of different classes of secondary metabolites. Results: In-vitro cytotoxic activities of the two extracts were significantly different (P ¼ 0.05). The methanol extract exhibited higher activity (IC50 ¼ 55.01 μg/ml). Phyto-chemical screening of the two extracts revealed the presence of terpenoids, phenols, steroids 26.02 μg/ml) compared to that of dichloromethane: methanol (1:1) (IC50 ¼ and flavonoids. Conclusion: The high in-vitro anti-cancer activities of solvent extracts of Kigelia africana justify its use in traditional medicine to manage breast cancer. Phytochemical analysis of the extracts reveal similar profiles hence the differences in their anti-cancer activities can be attributed to quantitative variations of various classes of secondary metabolites.
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    Phenolic and Monoterpenoid Mosquito Repellent Constituents of Headspace Vapors of Conyza newii
    (2013-01) Mayeku, Philip Wafula; Sauda, Swaleh; Ahmed, Hassanali
    The plant Conyza newii has been reported to posses, mosquito repellent and fumigant toxicity properties. In this study headspace vapors emitted by the plant were obtained by adsorption on porapak Q® through headspace trapping under field conditions in West Pokot (35oE, 1oN) and Kericho (35oE, 0o) and analyzed using Gas Chromatography-Mass Spectrometry and co-injection with authentic standards. Mosquito repellency bioassays of volatiles and their synthetic blend were carried out according to the World Health Organization protocol for evaluation of repellents. Five major compounds identified in the volatiles were trans-limonene oxide, cislimonene oxide, cis-dihyrocarvone, 4-methoxyphenol and 3-ethoxy-2-methyl phenol (2:2:2:2:1). Authentic standards of the compounds were bioassayed against Anopheles gambiae s.s and the three of them, trans-limonene oxide, cis-dihyrocarvone and 4-methoxyphenol exhibited repellency of RD50 = 9.2 × 10-5 mg cm,-2, 95% CL, RD50 = 5.4 × 10-4 mg cm,-2, 95% CL and RD50 = 6.7 × 10-4 mg cm,-2, 95% CL respectively.Synthetic blend of the three compounds in their natural ratio (1:1:1) exhibited higher repellency (6.2 × 10-5 mg cm-2) than the individual compounds and even the oil of the plant obtained through steam distillation.
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    Thalictramine, A new alkaloid from Thalictrum rhyncocarpum (Dill & Rich) and its anti-bacterial activity
    (2014) Mayeku, Philip Wafula; Odalo, J. O.; Hassanali, A.; Kiremire, B. T.; Hertweck, C.
    Thalictrum rhyncocarpum, a creeping plant with fern-like leaves, is used in herbal medicine to treat various infections in parts of Africa. Previously, we reported In-vitro anti-bacterial activity of different parts (root, stem bark and leaves) of the plant. In this study, bioassay-guided chromatography of an active fraction of ethanol extract of the plant against Staphylococcus aures-SG 511, Pseudomonus aeruginosa-K799/61 and Mycobacterium vaccae- 10670 (using tube dilution method) was undertaken. Two bioactive constituents were isolated from an active fraction of the extract and characterized using spectrometric methods as thalictramine (1) and berberine. In addition, 6-O-β-D-glucopyranosyl-D-glucose (gentiobiose) was also isolated from the same fraction. The antibacterial activities of the active fraction, thalictramine and berberine against P. aeruginosa and M. vaccae were higher than that of ciprofloxacin.