The Role of Medicinal Plants in the Treatment of Diseases Caused by Micro-organisms (A Study of Pawpaw, Guava, and Neem Leaves)
Chapter One
Aims of the Study
This work aims to investigate the role of medicinal plants in treating diseases caused by microorganisms and also investigate the chemical compounds present in the leaves of these medicinal plants.
CHAPTER TWO
LITERATURE REVIEW
Natural Plant Products and Medicine
The early medicines of man were obtained from natural sources; empiricism, superstition and traditional medicinal folklore have guided man to find healing in herbs and barks, fruits, leaves, roots, seeds, and stems of plants under different climates in different parts of the world. Lichens and Fungi have also had their share as contributive sources of drugs for centuries (Sofowora, 1989).
Although plants are unique in their activities, but it has also been found that a particular plant may be used by different tribes or countries for different ailments, this shows that plant possesses a very wide range of healing powers which is attributed to the natural plant products which constitute their chemical composition.
Plants are immensely complicated factories, which turn the relatively simple ingredients of air and water into enzymes, sugar, protein, solid cellulose, liquid oils, and scents to attract pollinating insects and poison to kill off predators, and also producing secondary metabolites to combat diseases (Mabey, 1977).
Medicinal Plants
Ethno-medicinal study is today recognized as the most viable method of identifying new medicinal plants or refocusing on those earlier reported for brochure constituents (Farnsworth, 1990). For thousands of years, Africans have relied on medicinal plants and its knowledge thereof, to treat ailments (Van Wyk et al., 1997).
Medicinal plants are capable of synthesizing an overwhelming variety of low-molecularweight compounds. Presently, 100,000 such compounds have been isolated from higher plants (Verpoorte and Memelink, 2002). The biosynthesis of secondary metabolites varies among plants even in different organs of plants (Khan et al., 2010).
The use of medicinal plants predates the introduction of antibiotics and other modern drugs into the African continent. Africans have been able to cure a lot of diseases by using concoctions made from different plants, and these have been passed from generation to generation.
Plants have been used as sources of traditional drugs and pharmaceutical preparations for man and other animals. According to a survey by the Uanited Nations Commission for Trade and Development (UNCTAD, 1974), more than 33% of modern drugs and medicinal products are derived from plants (UNCTAD, 1974).
Medicinal plants have always played a key-role in the world health, since they are the sources of many important scientific drugs of modern world (UNCTAD, 1974). It is not a surprise that the earliest drugs in the history of medicine were all derived from plants e.g.
Quinine derived from the bark of cinchona
Morphine derived from seed capsules of opium poppy
Penicillin derived from the mould Penicillum notatum
Acetylsalicylic derived from the willow bark, used originally for headaches, and has both analgesic and anti-pyretic properties
Colechine derived from the root of meadow saffron (Mabey, 1977).
Medicinal herbs have been used for healing as an alternative to medicine by all cultures for several thousands of years. About 80% of the world‟s population does not have access to conventional drugs and therefore rely on medicinal herbs (Abugassa et al., 2008).
CHAPTER THREE
MATERIALS AND METHODS
The fresh leaves of the plants were collected and identified by a Taxanomist in Michael Okpara University of Agriculture, Umudike, Umuahia, Abia State, Nigeria.
Preparation of the extracts
Ten gram each of the plant leaves was oven dried at a temperature of 500C for 24hrs before being processed to flours using a food processor and stored in an air tight container prior to analysis.
Determination of tannin content
The percentage composition of tannin in the plants was determined using the AOAC methods (1980) with some modifications. Folin-Denis reagent and saturated sodium carbonate were prepared in accordance with the procedure to analyze the tannin content. Standard solution of tannic acid was freshly prepared by dissolving 10 mg of tannic acid in 100 ml water. A series of tannic acid standard were prepared in the range of 0-2.5 ml aliquots in 25 ml volumetric flasks then added with 1.25 ml Folin-Denis reagent and 2.5 ml sodium carbonate solution. The mixture was made up to the volume and the color was measured after 30 min at 760 nm using a spectrophotometer (Perkin Elmer).
CHAPTER FOUR
RESULTS AND DISCUSSION
Tannins are dietary anti-nutrients that are responsible for the astringent taste of foods and drinks (Chikezie et al., 2008). Tannins bind to both proteins and carbohydrates which has several implications for commodities containing tannins. Their presence can cause browning or other pigmentation problems in both fresh foods and processed products. The presence of tannin in the plants implies they may have astringent properties and in addition, could quicken the healing of wounds and burns (Farquar, 1996). This justifies their usage in herbal medicine.
CHAPTER FIVE
CONCLUSION
All the different species of plant leaves that were assayed contained significant quantities of saponin and cyanide though in moderate levels suggesting that they may not be deleterious to the user. They were also observed to contain high quantities of alkaloids and flavonoids suggesting their antioxidant potentials and justifying their therapeutic uses which could be utilized in drug formulation. Finally, the low quantities of tannin in all the plants studied suggest that usage of these plants in herbal medicine can neither interfere with dietary iron absorption nor inhibit digestive enzymes.
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