ABSTRACT
This study focused on the identification of mistletoe species parasitic on Terminaliamantaly, Terminaliacatappa, Citrus grandis, Khayasenegalensisand Albizzialebbeck as well as the determination of the qualitative and quantitative phytochemical constituents and antibacterial activities of the leaf extracts of the host trees and their associated mistletoes. Fresh leaves of the mistletoes and their host trees were collected from four sampling areas within ABU campus, Samaru, Zaria, Nigeria. The leaves were air dried and pulverized. Maceration method was used for the extraction of the plant constituents. The susceptibility test of the samples on Staphylococcus aureus, Bacillussubtilis, Escherichia coliand Salmonellatyphiwas carried out using agar well diffusion method. The study revealed that, Tapinanthusglobiferus, Globimetulabraunii and Globimetulaoreophila were found parasitic on most of the host plant species exceptG. oreophila on Terminaliacatappa; Englerinalecardii was found parasitic only on Albizzialebbeckand Citrus grandis; Tapinanthusdodoneifolius was parasitic on T. catappa and A. lebbeck and Tapinanthusbelvisii was found parasitic on A. lebbeck, T. catappa and Terminaliamantalyrespectively. The qualitative phytochemical screening revealed the presence of tannins, saponins, flavonoids, cardiac glycosides and carbohydrates in both the ethanolic and aqueous leafextracts of most of the host plants and the mistletoes on them. Steroid was found present only in the aqueous extract of G. braunii from C. grandis and A. lebbeck, but was found in most of the extracts of Khayasenegalensis and the mistletoe species on it. The quantitative phytochemical screening revealed that cyanogenic glycosides and flavonoidshad the highest (31.00 %, in T. globiferusand 22.40 %, in K. senegalensisrespectively) concentrations than all the other compounds in both the host plants and attached mistletoes while phenols and tannins had the lowest (0.41 mg/ml, in C. grandis and 0.08 %, in G. brauniirespectively) concentrations than all the other compounds. The antibacterial activity of the aqueous leaf extracts of the host trees and associated mistletoes revealed that T. mantaly, C. grandis and A. lebbeckwereactive against most of the test organisms (S. aureus, B. subtilis, E. coliand S. typhi.) at the concentration ranging from 25 to 200 mg/ml except T. catappa extract, which was only active against S. aureus. Similarly, the extracts of mistletoes obtained from the host plants except the ones from T. mantaly and A. lebbeckwere also active against virtually all the test organisms. The control (ciprofloxacin), however, was the most active against all the test organisms compared to the plant extracts. In conclusion, this study showed thatA. lebbeck was the most parasitized host tree in the study area compared to other hosts. All the aqueous leaf extracts of the host trees with the mistletoe species sourced from them except the mistletoes from T. mantaly and A. lebbeckrespectivelyhad an antibacterial activityat concentration ranging from 25 to 200 mg/ml on S. aureus, B. subtilis, E. coliand S. typhi.
CHAPTER ONE
1.0 INTRODUCTION
1.1 Preamble
Mistletoe consists of about 1400 species around the world and belongs to the kingdom Plantae, subkingdom Tracheobionta, superdivision Spermatophyte, division Magnoliophyta, class Magnoliopsida, subclass Rosidae, order Santales (Judd et al., 2002). Recent phylogenetic works confirm that mistletoes belong to five distinct families: Misodendronaceae, Eremolepidaceae, Santalaceae, Viscaceae and Loranthaceae (Der and Nickrent, 2008; Malecot and Nickrent, 2008; Vidal-Russell and Nickrent, 2008). The largest family of this mistletoe is Loranthaceae which has 75 genera and over 900 species (Judd et al., 2002). Six major genera are found in Nigeria namely: Tapinanthus, Agelanthus, Loranthus, Globimetula, Phragmanthera and Englerina. Tapinanthus is far more widespread in the Nigeria savanna (Johri and Bhatnagar, 1972; Omolaja and Gamaye, 1998). In Nigeria, mistletoe is called ‗afomo‘in Yoruba, ‗apari‘ in Igbo,it is ‗kauci‘ in Hausa and ‗children‘s matches‘ in Eastern Cameroon presumably due to the match-like shape of the flower (Oluwole et al., 2013). Mistletoes plants grow on a wide range of host trees, it affects their growth and can kill them with heavy infestation.
All mistletoes are hemi-parasites, bearing evergreen leaves that photosynthesize but depend on their host mainly for water and mineral nutrients (Milius, 2000). Most mistletoe seeds are spread by birds that eat the fruits (Cowles, 1964). The mistletoe seed germinates on the branch of a host tree or shrub and in its early stages of development it is independent of its host. Later, it forms a haustorium that penetrates the host tissue and takes water and nutrients from the host plant (Milius, 2000). Various studies carried on the phytochemical constituents of mistletoes indicated the presence of glycosides, alkaloids, viscotoxins, phenylpropannoids, tannins and sugars (Jurin, 1993). Inuwa et al. (2012) reported that the phytochemical screening of Globimetula braunii indicated the presence of alkaloids, tannins, flavonoids and steroids. Mistletoes have alsobeen reported to be used for the treatment of cancer, hypertension, diabetes, arthritis, heart problems, insomnia, infertility and pneumonia (Obatomi et al., 1994; Osadebe and Ukwueze, 2004; Adodo, 2006; Uzochukwu and Osadebe, 2007; Osadebe and Omeje, 2009; Jadhav et al., 2010). Kafaru (1994) further ascertained that they are very potent in curing circulatory problems and also as anticancer agents. According to Blumentha et al. (1998), the extracts from the leaves of Globimetula braunii stimulate insulin secretion from pancreatic cells and help in the treatment of arthritis. Mistletoe plants have also been shown to have broad spectrum of antimicrobial properties against certain drug resistant bacteria and fungal organisms of farm animals (Deen and Sadiq, 2002).
The growth of mistletoes on different kind of plants, is of disease curing specificity, for example, mistletoes grown on guava, kolanuts and citrus arespecific for curing diseases like cancer, hypertension, nervousness and insomnia, while those grown on cocoa are best used for curing diabetes (Ekhaise et al., 2010). Although, without any literature supporting the claim, inhabitants of Michika local government area of Adamawa State, Nigeria, have indicated that mistletoe plants parasitizing lemon trees are more effective for treating people suffering from typhoid, pneumonia and hypertension than any other mistletoe (though not being specific of the mistletoe species type) found on other trees species. This could be due to the differences in host tree species composition as indicated by Scheer et al. (1992), Obatomi et al. (1994), Wagner et al. (1996) as well as Osadebe and Ukwueze(2004) who reported that, the composition and activities of mistletoes are host tree and season dependent. However, in order to prove or disprove the claim that mistletoes growing on lemon trees are more effective against typhoid, pneumonia and hypertension than the ones parasitic on other trees, the need for this study is necessitated.
Ndamitso et al. (2013) in in vitro assay of the extracts of Tapinanthus dodoneifolius using agar plate-hole and nutrient broth dilution techniques, revealed a wide spectrum of antimicrobial activities against certain multiple drug resistant bacterial isolates with Salmonella typhi and Staphylococcus aureus being the most susceptible while Bacillus subtilis was the least. Inuwa et al. (2012) reported in their research on the phytochemical and antimicrobial activities of Globimetula braunii that, the ethanolic and aqueous extracts inhibited the growth of Klebsiella aerogenes, Proteus spp., Escherichia coli and Pseudomonas aeruginosa. Some herbalists in Samaru claimed to have been using mistletoe parasitic on locust beans (Parkiabiglobosa) for cleansing of Sorghum bicolor (guinea cornseed) so as to clear it of fungi responsible for blacksmut disease of guinea corn. The mistletoes are also used by themfor curing of pile and fever (Personal communication).
1.2 Statement of the Research Problem
Most of the currently used antibacterials are associated with adverse effects such as blood cancer, upper gastrointestinal complications, organ damages, toxicity, hypersensitivity, immunosuppression and tissue residues, thus posing public health hazard (Calixto, 2000). Also, these synthetic broad spectrum antibiotics are cost prohibitive and are not within the reach of the poors. And moreso, pathogens are now developing resistance to most of these synthentic drugs (Calixto, 2000).
There is a controversy among some groups of people in Michika local government area of Adamawa State, Nigeria on the efficacy of the mistletoes found on lemon trees in contrast with that on other trees species on the causal agents of typhoid, pneumonia (Salmonella typhi and Staphylococcus aureus) and as a remedy to hypertension than any other mistletoes found on other trees species.
1.3 Justification for the Research
Many plant constituents have proven effective as remedy for some diseases and accounted for about seven thousand pharmaceutically important compounds in western pharmacopeia and a number of important drugs, like taxol and artemisinin ( Aderogba et al., 2004). Moreso, the use of plant extracts and phytochemicals, with known antimicrobial properties, can be of great significance in therapeutic treatments (Prusti et al., 2008).
During recent years, considerable work has been done to investigate the pharmacological importance of mistletoes on scientific lines, but not much work has been reported so far on comparative pharmacological importance of the plant growing on different host trees (Ilesanmi and Olawoye, 2010; Yusuf et al., 2013). Therefore, it is imperative to compare the phytochemical composition and antibacterial activity of different species of mistletoe obtained from the same and different host trees that are known to have antimicrobial effect.
The results obtained from this study will help determine mistletoe-host relationship and its efficacy on the causal agents of typhoid and pneumonia (Salmonella typhi and Staphylococcus aureus) and will also provide a reliable explanation to variations in the antimicrobial activity of mistletoe species in relation to their hosts.
1.4 Aim of the Research
The aim of the research was to study the phytochemical composition and antibacterial activity of some species of mistletoe and five host trees in ABU Campus, Zaria, Nigeria.
1.5 Objectives of the Study
The objectives of this study were to:
- Determine the species of mistletoe parasitic on Terminalia catappa, Citrus grandis, Terminalia mantaly, Khaya senegalensis and Albizzia lebbeck.
- Determine the qualitative and quantitative phytochemical composition of the mistletoes‘ host plants.
- Determine the qualitative and quantitative phytochemical composition of different species of mistletoe obtained from the same and different host trees.
- Determine the antibacterial activities of the extracts of the mistletoes‘ hosts: Terminalia catappa, Citrus grandis, Terminaliamantaly, Khaya senegalensis and Albizzia lebbeck.
- Determine the antibacterial activities of the extracts of different species of mistletoe obtained from the same and different host trees such as Terminalia catappa, Citrus grandis, Terminaliamantaly, Khaya senegalensis and Albizzia lebbeck.
1.6 Hypotheses
- There is no significant difference in the species of mistletoe parasitic on Terminalia catappa, Citrus grandis, Terminalia mantaly, Khaya seneglensis and Albizzia lebbeck.
- There is no significant difference in the qualitative and quantitative phytochemical compositions of the mistletoes‘ hosts.
- There is no significant difference in the qualitative and quantitative phytochemical compositions of different species of mistletoe obtained from the same and different hosts.
- There is no significant difference in the antibacterial activities of the extracts of the mistletoes‘ hosts: Terminalia catappa, Citrus grandis, Terminaliamantaly, Khaya senegalensis and Albizzia lebbeck.
- There is no significant difference in the antibacterial activities of the extracts of different species of mistletoe obtained from the same and different host trees such as Terminalia catappa, Citrus sp., Terminaliamantaly, Khaya senegalensis and Albizzia lebbeck.
