Chemical composition and antimicrobial activity of the essential oil of Ocimum gratissimum L. growing in Eastern Kenya

Hydro-distilled volatile oils from the leaves of Ocimum gratissimum L. (Lamiaceae) from Meru district in Eastern Kenya were analysed by gas chromatography-mass spectrometry (GC-MS) and also evaluatedfor antimicrobial activity. The oil was dominated by monoterpens which accounted for 92.48%. This monoterpene fraction was characterized by a high percentage of eugenol (68.8%). The other major monoterpenes were methyl eugenol (13.21%), cis-ocimene (7.47%), trans-ocimene (0.94%), -pinene (1.10%) and camphor (0.95%). The sesquiterpenes present in fairly good amounts were germacrene D(4.25%) and trans-caryophyllene (1.69%). The minor  sesquiterpenes were -farnesene (0.85%) and -bisabolene (0.74%). The antimicrobial activities of the essential oils were evaluated against both Gram positive (Staphylococcus aureus, Bacillus spp.) and Gram negative (Escherichia coli, Pseudomonasaeruginosae, Salmonella typhi, Klebisiella pneumoniae, Proteus mirabilis) bacteria and a pathogenic fungus Candida albicans. The oil had pronounced antibacterial and antifungal activities on all themicrobes

Phytochemical constituents and antimicrobial activity of leaf extracts of three Amaranthus plant species

This study investigated the phytochemical constituents and antimicrobial activity of hexane, ethyl acetate, dichloromethane and methanol leave extracts of Amaranthus hybridus, Amaranthus spinosus and Amaranthus caudatus. The microorganisms assayed for antimicrobial activity were: the grampositive Staphylococcus aureus and Bacillus spp, the gram-negative Escherichia coli, Salmonella typhi, Pseudomonas aeruginosae, Proteus mirabillis and Klebsiella pneumoniae and a pathogenic fungus Candida albicans. The leave extracts showed a broad spectrum anti-bacterial activity but resistance to the fungus. Commonly encountered phytochemical constituents in the leaf extracts of the three Amaranthus species included flavonoids, steroids, terpenoids and cardiac glycosides. The minimum inhibitory concentration (MIC) exhibited by A. spinosus extracts against the Salm. typhi was 129 mg/ml. The MIC exhibited by A. hybridus extracts against the tested organisms ranged between 200 and 755 mg/ml whereas that of A. caudatus was between 162.2 and 665 mg/ml. The antimicrobial properties of these plants which have been used by mankind for centuries without any signs of toxicity can be used in the traditional herbal medicines which play a very important role in primary care systems in the developing world and are becoming increasingly popular in the developed world

Biotechnological tools for improvement of black nightshade (Solanum nigrum L. complex), valuable medicinal and vegetable plants in Kenya

Solanum nigrum complex is a group of plant species used as indigenous vegetables but also as traditional medicinal plants in Kenya and other parts of the world. In Kenya, just like in most African countries, both the unripe fruits and leaves are used to cure different ailments. This vegetable is said to improve the CD4 count in HIV patients and all HIV patients are encouraged to take it as part of their diet. Despite that high value, African nightshade is a neglected crop. Up to now the farmers exploit traditional landraces and accessions. For development of improved African S. nigrum varieties, knowledge is necessary about the genetic structure of the local African nightshade accessions. Amplified fragment length polymorphism (AFLP) technique was performed to discriminate accessions from the Western region of Kenya. Production of haploid plants of the S. nigrum complex and subsequent chromsome doubling is a promising tool to obtain pure inbred lines in a short time. Therefore, in this study, anthers of S. nigrum were cultivated in vitro. It was observed that the microspores underwent the first divisions and calluses were formed

VOLATILE LEAF OIL CONSTITUENTS OF OCIMUM AMERICANUM L. OCCURING IN WESTERN KENYA

Steam distilled volatile oils from the leaves of Ocimum americanum L. growing in Western Kenya were analysed by GC and GC-MS. A total of 36 compounds, representing a total of 88.51% of the total oil, were identified. The oil was classified as terpinen-4-ol-type according to the terpinen-4-ol content (43.21%). To the best of our knowledge this chemotype of O. americanum has not yet been reported from the East African region. This chemotype of O. americanum has only been reported from Togo. Other notable components include 1,8-cineole (16.13%), α-terpineol (4.01%), trans-caryophyllene (3.06%), α-bergamotene (2.68%) and cis-sabinene hydrate (2.59%). The oil contains mainly oxygenated monoterpenes which accounted for 71.24% of the total oil. The yield obtained was 4% w/w on a dry weight basis. KEY WORDS: Ocimum americanum, Lamiaceae, Chemotype, Terpinen-4-ol, 1,8-Cineole, µ-Terpineol, trans-Caryophyllene, Kenya Bull. Chem. Soc. Ethiop. 2006, 20(1), 177-180

Chemical composition and larvicidal activity of essential oil of Lippia kituiensis against larvae of Rhipicephalus appendiculatus

This study evaluated the larvicidal activity of essential oil of Lippia kituiensis leaves against larvae of Rhipicephalus appendiculatus. The oil was obtained by hydro-distillation of fresh leaves and analysed using Gas Chromatography-Mass Spectrometry (GC-MS). Analysis showed that sesquiterpenes were dominant (56.57%), followed by monoterpenes (36.36%), diterpenes (2.59%) and others (5.19%). Major sesquiterpenes were germacrene D, β-bourbonene, gamma cadinene and 2-isopropyl-5-methyl-9-methylene-bicycle (4.4.0)dec-1-ene. Major monoterpenes were (1S, 4S)-(-)-camphor, trans-sabinene hydrate, gamma-terpinene, dl-limonene, alpha-terpinolene, l-Phellandrene, beta-Myrcene, sabinene, camphene, alpha-pinene, 4-terpineol, 4-methyl-1-(1-methylethyl)-3-cyclohexen-1-ol, 14.29 borneol (=endo-borneol), camphore, and neo-alloocimene. At 6, 12, 24, and 48 hrs after larval treatment, the oil showed activity against R. appendiculatus larvae with LC50in mg/ml of 3.26(3.14-3.38), 3.21(3.08-3.32), 3.15(3.03-3.26), 3.09(2.97-3.20) while LC90in mg/ml were 4.15 (3.95-4.45), 4.03 (3.85-4.30), 3.94 (3.77-4.19), 3.86 (3.69-4.09) respectively. Results of one way ANOVA (Analysis of Variance) showed there was no significant difference in activity of the oil against the larvae, between 6, 12, 24 and 48 hrs in all the concentrations used P = 0.97, 95% confidence. The findings indicatedthat essential oil of L. kituiensis possessed larvicidal properties and can be used to control tick larvae.Keywords: Rhipicephalus appendiculatus; essential oils; acaricidal activity, ticks

Sesquiterpene lactones from Vernonia cinerascens sch. bip. and their in vitro antitrypanosomal activity

In the endeavor to obtain new antitrypanosomal agents, particularly sesquiterpene lactones, from Kenyan plants of the family Asteraceae, Vernonia cinerascens Sch. Bip. was investigated. Bioactivity-guided fractionation and isolation in conjunction with LC/MS-based dereplication has led to the identification of vernodalol (1) and isolation of vernodalin (2), 11β,13-dihydrovernodalin (3), 11β,13-dihydrovernolide (4), vernolide (5), 11β,13-dihydrohydroxyvernolide (6), hydroxyvernolide (7), and a new germacrolide type sesquiterpene lactone vernocinerascolide (8) from the dichloromethane extract of V. cinerascens leaves. Compounds 3-8 were characterized by extensive analysis of their 1D and 2D NMR spectroscopic and HR/MS spectrometric data. All the compounds were evaluated for their in vitro biological activity against bloodstream forms of Trypanosoma brucei rhodesiense and for cytotoxicity against the mammalian cell line L6. Vernodalin (2) was the most active compound with an IC50 value of 0.16 µM and a selectivity index of 35. Its closely related congener 11β,13-dihydrovernodalin (3) registered an IC50 value of 1.1 µM and a selectivity index of 4.2

Genetic variability of tissue cultured Sorghum bicolor (L) Moench as revealed by morphological traits and simple sequence repeats (SSR) markers

To evaluate their performance for seedling traits at seedling stage (under hydroponics), plant water relations under water stress and ultimately grain yield, and to estimate the genetic variability of the regenerates, the parent plants of local sorghum cultivars in Kenya using simple sequence repeats (SSR) markers were analyzed. The research involved Seredo, El Gardam and Mtama 1 sorghum cultivars. The TC (Tissue culture) regenerates were produced through somatic embryogenesis in Linsmaier and Skoog (LS) media augmented with an osmoticum, NaCl (100 mM) in attempt to improve the parent plant for water stress tolerance. The genetic variability was investigated using five SSR markers and seven morphological traits associated with water stress tolerance. The amplified DNA fragments were screened by gel electrophoresis using 2% agarose. Cluster and principal component analysis (PCA) were done using NTSYS-pc version 2.2. The SSR detected 11 alleles with an average of 2.2 alleles per locus. The number of alleles per locus ranged from two to three and the allelic polymorphism information content (PIC) value ranged from 0.344 for Xcup14 to 0.730 for Xgap72 with an average of 0.559. These results show that the cultivars differed for morphological and SSR markers. The average genetic similarity based on the morphological traits (0.922 with a range of 0.845 to 0.989) was higher than SSR markers (0.625 with a range of 0.306 to 0.944). The results also show that the classification of these sorghum cultivars may be useful to the breeders to plan crosses for preferred traits. The results also show that the sorghum microsatellites can be used to distinguish the cultivars and to estimate genetic diversity due to somaclonal variation. Overall, this study shows that tissue culture technique might not add value in producing somaclonal variation in sorghum.Key words: Cultivars, tissue culture regenerates, water stress tolerance, simple sequence repeats

Evaluation of nutritional properties of tissue cultured sorghum [Sorghum bicolor (L) Moench]

Tissue culture techniques are commonly used in plants as an efficient way to propagate and store valuable genotypes. Often, some of the regenerants differ from the parental type, a phenomenon called somaclonal variability. Assessment of nutritional value variability in crops that may arise from somaclonal variability during tissue culture propagation may have a strong impact on plant breeding, conservation of genetic resources and nutrition in the areas of use. It is particularly useful in the characterization of individual cultivars, and in determining duplications in germplasm collections and for selecting parents. The Sorghum bicolor (L) Moench tissue culture (TC) regenerants (Seredo, Mtama 1 and El Gardam) were developed at the Jomo Kenyatta University of Agriculture and Technology towards improvement for water stress tolerance for improved food production in the ASALs in Kenya. The study was conducted to evaluate the nutritional value of the parents and TC regenerants of Sorghum bicolor (L) Moench local cultivars (Seredo, Mtama 1 and El Gardam) in Kenya. For proximate composition significant (p≤0.05) differences were observed in parents and regenerants of the El‐Gardam (moisture, proteins and crude fiber), Mtama 1 (proteins) and Seredo (fats and crude fiber). The mineral compositions of the parents and regenerants of the cultivars were not significantly different (p ≤ 0.05) except for Zinc in Mtama 1 cultivar and Iron in both El‐Gardam and Mtama 1 cultivars. B‐vitamins showed significant differences (p ≤ 0.05) for both thiamine and Pyridoxine in El‐Gardam and Seredo. Significant variability (p ≤ 0.05) was shown phytates content in each cultivar. The parents were observed to have significantly higher amounts of Phytates than the regenerants within all the cultivars. The study recommends Mtama 1 regenerants with low anti‐nutrient appropriate for ASALs with respect to nutrient availability since anti‐nutrients in sorghum have been shown to impair the bioavailability of the other nutrients to the body.Key words: Cultivars, TC regenerants, water stress tolerance, nutritional valu

ANTIMICROBIAL ACTIVITY OF ESSENTIAL OILS OF OCIMUM GRATISSIMUM L. FROM DIFFERENT POPULATIONS OF KENYA

Hydro-distilled volatile oils from the leaves of Ocimum gratissimum L. (Lamiaceae) of 13 populations of different silvicultural zones were evaluated for antimicrobial activity against Gram positive (Staphylococcus aereus, Bacillus spp.) and Gram negative (Escherichia coli, Pseudomonas aeruginosa, Samonella typhi, Klebisiella pneumoniae, Proteus mirabilis) bacteria and a pathogenic fungus, Candida albicans. All the essential oils are active to the tested microbiles with different strength. The highest antimicrobial activity against Gram positive bacteria (Staphylococcus aureus) and Gram negative bacteria (Pseudomonas aeruginosae and Proteus mirabilis) was observed from the eastern Kenya (Meru) oil. Meru oil was the best and its effectiveness was consistent on nearly all the microbes tested. The oil from the plant growing in the coastal region of Kenya (Mombasa) showed the best effect only on Gram negative bacteria (Escherichia coli and Proteus mirabilis). Both oils (Meru and Mombasa) were dominated by monoterpenes accounting for 92.48 % and 81.37 % respectively. The monoterpene fraction was characterized by a high percentage of eugenol (68.8 %) for Meru oil and 74.10 % for Mombasa oil. The other major monoterpene was methyl eugenol (13.21 %). Camphor (0.95 %) was observed only in the Meru oil. (Cis)-Ocimene, (trans)-ocimene and β-pinene were present in both Meru and Mombasa oils. The sesquiterpenes present in fairly good amounts in both oils were germacrene D and (trans)-caryophyllene. The minor sesquiterpenes were α-farnesene (0.85 %) and β-bisabolene (0.74 %) which were present in the Meru oil only

Chemical Composition and Antimicrobial Activity of the Essential Oil of Kumquat (Fortunella crassifolia Swingle) Peel

The aim of this study was to determine the main constituents of the essential oil isolated from Fortunella crassifolia Swingle peel by hydro-distillation, and to test the efficacy of the essential oil on antimicrobial activity. Twenty-five components, representing 92.36% of the total oil, were identified by GC-MS analysis. The essential oil showed potent antimicrobial activity against both Gram-negative (E. coli and S. typhimurium) and Gram-positive (S. aureus, B. cereus, B. subtilis, L. bulgaricus, and B. laterosporus) bacteria, together with a remarkable antifungal activity against C. albicans. In a food model of beef extract, the essential oil was observed to possess an effective capacity to control the total counts of viable bacteria. Furthermore, the essential oil showed strongly detrimental effects on the growth and morphological structure of the tested bacteria. It was suggested that the essential oil from Fortunella crassifolia Swingle peel might be used as a natural food preservative against bacteria or fungus in the food industry