ABSTRACT
The morphological and phytochemical characteristics of Laportea aestuans (L.) Chew and Laportea ovalifolia (Schumach.) Chew were studied. Major distinguishing morphological features of the stem were: height: 73.42 ± 4.66 and 38.77 ± 3.49; shape: angular and cylindrical; habit: erect and stoloniferous with erect shoots; colour: greenish and brownish or reddish; internode length: 5.92 ± 0.47 and 2.94 ± 0.08 respectively. Significant morphological differences in the leaves were: length: 12.39 ± 0.79 and 7.34 ± 0.43; Width: 9.74 ± 0.53 and 5.06± 0.43; Area: 100.68 ± 10.59 and 28.59 ± 2.24 and petiole length: 11.6 ± 0.74 and 6.33 ± 0.37 respectively. There were no significant differences in the length of stipules and pedicel: 0.77 ± 0.15 and 1.50 ± 0.50 respectively for the two species. However there were some similarities in the leaves, flowers and fruits of the two species: leaf shape- ovate; margin-serrated; apex- acute; base-cordate to rounded; phyllotaxy- alternately arranged; organization- simple; venation-reticulate; inflorescence- paniculate; flower- unisexual; calyx and corolla undifferentiated giving rise to perianth with five tepals and stamens in male flowers and four tepals in female flowers; fruits- ovoid achenes, laterally compressed. Phytochemical screening conducted on the stem and leaves of the two species revealed the presence of alkaloids, tannins, terpenes, saponins, flavonoids and cardiac glycosides and the absence of anthraquinones in both plants species. The morphological and phytochemical characters observed here confirm the relatedness of the species.
CHAPTER ONE
1.0 INTRODUCTION
Morphological as well as phytochemical characteristics can be used as important tools in the characterization of plants. Plant morphology or phytomorphology is the study of the physical form and external structure of plants. It represents a study of the development, form, and structure of plants, and by implication an attempt to interpret these on the basis of similarity of plan and origin (Harold, Alexopoulos and Delevoryas, 1987). Generally the principles of biological organization, that is, the internal interrelationships of all processes and structures in a plant are manifested in the plant’s external form. As such the external morphology of a plant is useful in the visual identification of that plant (Raven, Evert, and Eichhorn, 2005).
The morphology of a plant is considered distinct from anatomy which is the study of the internal structure of plants, especially at the microscopic level (Evert and Esau, 2006). Morphology observes both the vegetative (somatic) structures of plants, as well as the reproductive structures (Harold et al., 1987). The vegetative structures of vascular plants include the study of the shoot system, composed of stems and leaves, as well as the root system. The reproductive structures include the flowers, fruits and seeds and are usually specific to a particular group of plants. This area of morphology overlaps with the study of biodiversity and plant systematics (Harold, et al., 1987). Morphology is also comparative, meaning that it examines structures in many different plants of the same or different species, then draws comparisons and formulates ideas about similarities (Sattler, 1992). Making such comparisons between similar structures in different plants tackles the question of why the structures are similar. It is quite likely that similar underlying causes of genetics, physiology, or response to the environment have led to this similarity in appearance (Sattler, 1992). The result of scientific investigation into these causes can lead to one of these two insights into the underlying biology:
- Homology – the structures are similar between the two species because of shared ancestry and common genetics (Sattler, 1994).
- Convergence – the structures are similar between the two species because of independent adaptation to common environmental pressures (Sattler1994).
When structures in different species are believed to exist and develop as a result of common, inherited genetic pathways, those structures are termed homologous. Understanding which characteristics and structures belong to each type is an important part of understanding plant evolution (Sattler, 1992).
Phytochemicals are biologically active, naturally occurring chemical compounds found in plants, which provide health benefits for humans other than those attributed to macronutrients and micronutrients (Hasler and Blumberg, 1999). They protect plants from diseases and damage and also contribute to plant’s organoleptic properties like colour, aroma and flavour (Hamburger and Hostettmann, 1991). Recently, it is clearly known that phytochemicals have roles in the protection of human health, when their dietary intake is significant (Mamta, Jyoti, Rajeev, Dharmendra and Abhishek, 2013). In wide-ranging dietary phytochemicals are found in fruits, vegetables, legumes, whole grains, nuts, seeds, fungi, herbs and spices and they accumulate in different parts of the plants, such as in the roots, stems, leaves, flowers, fruits or seeds (King and Young, 1999). Many phytochemicals, particularly the pigment molecules, are often concentrated in the outer layers of the various plant tissues and their levels vary from plant to plant depending upon the variety and growing conditions (King et al., 1999).
Phytochemicals are classified as either primary or secondary depending on their role in metabolism. Primary constituents include the common sugars, amino acids, proteins, purines and pyrimidines of nucleic acids, and chlorophylls. Secondary constituents include alkaloids, flavonoids, glycosides, phenolics, saponins, tannins, essential oils and terpenes (Mamta et al., 2013). Secondary plant metabolites also referred to as natural products are renowned for their potent pharmacological activities; as antimicrobial, insecticidal, anticancer, antioxidant, pesticidal, amongst others. Some are odoriferous and find application in perfumes and cosmetics, for flavoring foods and drinks and for screening incense and household cleaning products (Narasinga, 2003). In recent years, there has been an extensive growth in natural product chemistry. This is due to advances in isolation, characterization, identification, purification and synthesis of new natural products. Much research has been performed to reveal the beneficial health effects of phytochemicals (Mamta et al., 2013).
Urticaceae, the nettle plants, is a family of flowering plants consisting of herbs, shrubs and trees (Hutchinson and Dalziel 1963; Hutchinson 1967; Heywood 1978). The family has 45 genera with about 700 species often with specialized stinging hairs, primarily distributed in the tropical regions (Heywood, 1978). The family name comes from the genus Urtica and includes a number of well-known and useful plants (Burkill, 1997).
Laportea Gaud. represents a prominent genus in the family Urticaceae and is composed of 22 species (Chew 1969, Yang et al 1996). Two species namely Laportea aestuans (Linn). Chew. and Laportea ovalifolia (Schumach.) Chew. formerly called Fleury a aestuans (Linn.) Miq. and Fleurya ovalifolia (Schumach. and Thonn.) respectively have so far been reported for southern Nigeria ( Essiett et al., 2011). The purpose of this research is to characterize these two species of Laportea using their morphological and phytochemical characteristics.
1.1 AIM AND OBJECTIVE S OF THE STUDY
The aim of the study is to morphologically and phytochemically characterize two species of Laportea (Laportea aestuans and laportea ovalifolia)
The objectives of the study include;
- To study the morphological characters of Laportea aestuans and Laportea ovalifolia, compare and contrast the observed morphological characters, and update information about the relatedness of these species.
- To extract and characterize the secondary metabolites (phytochemical) constituents of the plants, compare the diversity of phytochemicals in the two species and relate it to their medicinal uses.
- To delimit the two species of laportea using the findings above.
1.2 JUSTIFICATION FOR THE STUDY
Laportea aestuans and laportea ovalifolia has been widely spread as common weeds and are prominently used in traditional medicine. Therefore this study helps to enhance the delimitation of these two species morphologically and phytochemically and provide basic information that may steer further research into the medicinal efficacy of these two species.
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