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PHYTOCHEMICAL ANALYSIS ON PSIDIUM GUAJAVA LEAVES. TO EXTRACT THE ACTIVE COMPOUND RESPONSIBLE FOR ITS MEDICINAL ACTION USING SUCCESSIVE EXTRACTION

 CHAPTER ONE

1.0 Introduction

1.1 Background of Study

Plant-derived substances have recently become of great interest owing to their versatile applications (Baris, et al., 2006). Medicinal plants are rich bio-resources of drugs (Hamar et al., 1999). A number of interesting outcomes have been found with the use of a mixture of natural products or plant extracts to treat diseases (Gibbon, 2003). Medicinal plants are widely used in non-industrialized societies, mainly because they are readily available and cheaper than modern medicine. The annual global export value of the thousands of the types of plants with suspected medicinal properties was estimated to be US$2.2 billion in 2012.

The use of medicinal plants products as medicine can be traced as far back as the beginning of human civilization. The earliest mentioned medicinal plant used in Hindu culture is found in “Rigreda” which is said to have been written between 4500-1600BC and is supposed to be the oldest repository human knowledge. The active principle isolated, have provided leads in the development of several life saving drugs, which are in use today (Rastogi and Medrotta, 2002). Medicinal plants contain some organic compounds which provide definite physiological action on the human body and these bioactive substances include: Tannins, Alkaloids, Carbohydrates, Terpenoids, Steriods and Flavonoids (Edoga, et al., 2005). Numerous phytochemicals with potential or established biological activity have been identified. However, since a single plant contains widely diverse phytochemicals, the effects of using a whole plant as medicine are uncertain. Further, the phytochemical content and pharmacological actions, if any, of the plant remain unaccessed by rigorous scientific research to define efficacy and safety. Mainly, these compounds are synthesized by primary or rather secondary metabolism of living organisms. Secondary metabolites are chemically and taxonomically extremely diverse compounds with obscure functions. They are widely used in human therapy, veterinary, Agriculture, Scientific research and countless other areas (Vasu, et al., 2009).

Psidium guajava (guava) is well known tropic tree which is abundantly, grown for fruit. Many countries have a long history of using guava for medicinal purposes. This plant finds applications for the treatment of diarrhoea, dysentery, gastroenteritis, hypertension, diabetes, caries and pain relief and for improvement in locomotors coordination. Its leaf’s extract is being used as a medicine in cough, diarrhea and oral ulcers. It contains high content of organic and inorganic compounds like secondary metabolites e.g antioxidants, polyphenols, antiviral compounds, anti-inflammatory compounds.

1.2 Phytochemicals

Phytochemicals are non nutritive plant chemicals that have protective or disease preventive properties. They are non-essential nutrients meaning that they are not required human body for sustaining life. It is well-known that plants produce these chemicals to protect themselves but recent research demonstrates that they can also protect human against diseases. These are more than thousand known phytochemicals. Some of the well-known phytochemicals are: lycopene in tomatoes, isoflavones in soya and flavonoids in fruits.

1.2.1 How Phytochemicals Work

There are many phytochemicals and each works differently. These are some possible actions:

• Antioxidant: most phytochemicals have antioxidant activity to protect our cells against oxidative damage and reduce the risk of developing certain types of cancers. Phytochemicals with antioxidant activity. Ally sulphides (onions, leeks,garlic), carotenoids (fruits, carrots), flavonoids (fruits, vegetables).
• Hormonal action: Isoflavones, found in soy, imitate human estrogens and help to reduce menopausal symptoms and osteoporosis.
• Stimulation of enzymes: indoles, which are found in cabbages, stimulate enzymes that make the estrogen less effective and could reduce the risk of breast cancer. Other phytochemicals, which interfere with enzymes, are protease inhibition (soy and beans), terpenes (citrus fruits and cherries).
• Interference with DNA replication: saponin is found in beans interfere with DNA replication of cell DNA, thereby preventing the multiplication of cancer cell. Capsaicin, found in hot peppers, protects DNA from carcinogens.
• Antibacterial effect: the phytochemical alicin from garlic has antibacterial properties.
• Physical action: some phytochemicals bind physically to cell walls thereby preventing the adhesion of pathogens to human cell wall. Proanthocyanidins are responsible for the anti-adhesion properties of cranberry. Consumption of cranberries will reduce the risk of urinary tract infections and will improve dental health

1.3 Statement of Problem

Psidium guajava (guava) is a plant claimed to have a lot of economic value such as medicinal, nutritional and antimicrobial values, these claims have not been clearly justified. This research and experiment is therefore, centred on investigating, analysing and justifying the claims made on this plant and also to extract and identify the chemical composition responsible for the medicinal values of the plant.

1.4 Aims and Objectives

Phytochemical analysis on Psidium guajava leaves. To extract the active compound responsible for its medicinal action using successive extraction.

To clearly describe the unit operation [extraction process] used on this plant and to qualitatively identify the phytochemicals present in the plant.

1.5 Significance of the study

This research will give more knowledge about the plant psidium guajava.

1.6 Scope of the Study

The phytochemical analysis will be carried out on the leaves of the plant.