CHAPTER ONE

INTRODUCTION

1. BACKGROUND OF THE STUDY

Over 800 different species of eucalypts are indigenous to Australia (Vuong et al., 2015a). They are extensively planted for wood products and considered as one of the most important plants in the world (Gilles et al., 2010, Topçu et al., 2011, Gharekhani et al., 2012, Gupta et al., 2013). Eucalypts are a storehouse of both volatile and non-volatile compounds with a wide spectrum of biological activities. However, the volatile compounds found in the essential oils from eucalypts have so far, mostly been exploited for their application in the pharmaceutical and food industries. The Indigenous people of Australia have used eucalypts as traditional bush medicine to heal wounds and treat fungal infections since time immemorial (Gilles et al., 2010). Even though, eucalypts are native to Australia, they have been introduced throughout the tropics and subtropics including the Africa, Americas, Europe, the Mediterranean basin, the middle east, China and the Indian subcontinent for production of timber and paper (Gharekhani et al., 2012, Gupta et al., 2013). A number of more recent scientific studies have reported on the compounds present in the essential oils from eucalypts and their role as antimicrobials (Cimanga et al., 2002, Vilela et al., 2009, Gilles et al., 2010, Mulyaningsih et al., 2011, Fratini et al., 2014). However, there is little information available emphasising the potential antimicrobial properties of crude extracts from eucalypts. In addition, Eucalyptus microcorys is one of the least exploited Eucalyptus species in terms of its phytochemical content and biological activity.

During last three decades, numerous antibiotics have been produced, but the clinical efficiency of these existing antibiotics is being threatened by the emergence of multidrug resistant pathogens. According to World Health Organization (WHO), it was reported that medicinal plants would be the best source to obtain a variety of drugs. Antibiotic resistance has become a global concern in recent decades and there is a growing concern regarding the search for new antimicrobial substances from different sources of medicinal plants. The screening of plant extracts and plant products for antimicrobial activity has shown that higher plants represent a potential source of novel antibiotic prototypes (Kiruba, 2011).

The essential oils from the Myrtaceae family exhibit diverse biological activities like bacteriostatic, fungistatic and anti-inflammatory effects. Eucalyptus is one of the important genera of Myrtaceae family, a large genus of evergreen trees and shrubs containing about 700 species (Batish et al, 2008). Although most of the plants of this genera have their native origin in Australia and Tasmania (Oyedeji, 1999), but these have been cultivated in many other countries, including Tunisia and are used for its various properties. Around 500 species of eucalyptus produce essential oil. Eucalyptus are highly valued for their wood and are also a good source of proteins, tannins, and dyes although eucalyptus oil being the most valuable product. The oil can be readily distilled from their leaves (Sartorelli, 2007; Trivedi and Hotchandani, 2004). Eucalyptus oil is being extracted in many countries like China, India, South Africa, Portugal, Brazil and Tasmania on commercial scale. The other name of this plant is “forest red gum”, which was used traditionally for the treatment of wounds, boils and other ailments. The leaves can be obtained from trees grown solely for oil production. Eucalyptus has been known to be a good source of many natural substances exhibiting antagonistic activities against several microorganisms (Dwivedi and Dubey, 1986; Singh and Agrawal, 1988). Various volatile phytochemicals like isoprenoids are found in the leaves of eucalyptus which show a number of medicinal/antimicrobial properties (Olorundare et al, 1998). Eucalyptus extracts have been approved as food additives and are currently used in various cosmetics formulation. Saponins, tannins, steroids and flavonoids have been found in the leaf extract of eucalyptus. Alkaloids and flavonoids possess antimicrobial activity (Sartorelli et al, 2006).

1. STATEMENT OF THE PROBLEM

Development of multi-drug resistance pathogenic strains is one of the biggest concerns in today's world as it has adverse effects on the efficacy of medical and pharmaceutical treatments, as well as agricultural and food industries. Various factors such as overuse, inappropriate prescription, and extensive agricultural use of antibiotics and availability of very few new antibiotics contribute to the development of drug resistance in microorganisms (Ventola, 2015). Hence, there is an urgent need to look for novel antimicrobials, especially from nature. Plant phenolics and antioxidants have been extensively reported in the scientific literature for their antimicrobial potential (Davidson and Branden, 1981, Tomás-Barberán et al., 1990, Nicholson and Hammerschmidt, 1992, Cowan, 1999, Zhu et al., 2004, Proestos et al., 2005, Estevinho et al., 2008, Süzgeç-Selçuk and Birteksöz, 2011, Stojkovic et al., 2013, Gyawali and Ibrahim, 2014, Guil-Guerrero et al., 2016). Therefore, the present study evaluated the phytochemical, antioxidant, antibacterial and antifungal properties of the aqueous crude extract from one of the least explored Eucalyptus species: E. microcorys.

Nature has been a source of medicinal agents for thousands of years. Recently, research is being done on medicinal plants worldwide. Plants had been used for the healing of diseases ages ago before the use of recent clinical drugs. Such medicinal plants are also recognized to have therapeutic properties or as precursors for the synthesis of useful drugs (Sofowora, 1982). More than 50% of these synthetic drugs are derivative of natural products. These natural products play a crucial role in drug development (Jeyachandran et al, 2007). With the increasing use of chemicals, antibiotics many pathogens have developed resistance against them; hence there is immense need to develop new anti-agent with improved performance and wide applications. Certain plant extracts have shown antimicrobial properties against certain bacteria (Paster et al, 1990) and have been studied to be utilized as agro chemical with favorable antimicrobial activity (Kim et al, 1996).

Traditionally, eucalyptus leaves have been used to heal wounds and fungal infections. Eucalyptus leaves show many activities such as antioxidant, antiseptic and anti-inflammatory (Rai et al, 2013). Besides antimicrobial activity, the essential oil and its constituents also show herbicidal (Setia et al, 2007), insecticidal (Rudin 2005; Park and Shin 2005), anthelmintics (Bennet and Bryant, 1996), anti-tumor (Takasaki et al, 1995) and anti-leech (Kirton, 2005) activity. Keeping in view of these properties of eucalyptus, present study intend to investigate the following objectives

1. AIM AND OBJECTIVES OF THE STUDY

The aim of the study is to investigate Phytochemical analysis of Eucalyptus leaves extract.

Specifically, the study seeks to:

1. Examine the relationship between antimicrobial activity and phytochemical analysis of Eucalyptus globulus leaves.
2. Examine the extraction of eucalyptus oil from the leaves using methanol and acetone. 
3. Examine the phytochemical screening of different compounds present in leaves.

1. RESEARCH QUESTIONS

The following research questions will be addressed in the study:

1. What is the relationship between antimicrobial activity and phytochemical analysis of Eucalyptus globulus leaves?
2. What is the extraction of eucalyptus oil from the leaves using methanol and acetone?
3. What is the phytochemical screening of different compounds present in leaves?

1. STATEMENT OF THE HYPOTHESIS

H0 There is no significant effect of Phytochemical analysis of Eucalyptus leaves extract

H1 There is significant effect of Phytochemical analysis of Eucalyptus leaves extract

1. SIGNIFICANCE OF THE STUDY

Eucalyptus has been used as a medicinal plant from ages because of its various properties.

The study is very important because the phytochemical content of Eucalyptus leaves will be analyzed by soxhlet extraction of the dried leaves using methanol and acetone.

The study will also reveal whether maximum amount of phytochemicals present in eucalyptus leaves will be retained in methanolic extract. The methanolic extract contained quinones, saponins, carbohydrates, tannins, phenols, flavonoids & fat while in the acetonic extract quinones, flavonoids & fat was present.

The quantitative analysis of methanolic extract through the findings of the study will revealed an appreciable amount of antioxidant activity assessed by DPPH scavenging activity expressed in terms of ascorbic acid.

1. SCOPE OF THE STUDY

The study focuses mainly on the investigation Phytochemical analysis of Eucalyptus leaves extract.

Specifically, the interest of the study will be restricted to the relationship between antimicrobial activity and phytochemical analysis of Eucalyptus globulus leaves; the extraction of eucalyptus oil from the leaves using methanol and acetone; and the phytochemical screening of different compounds present in leaves.

1. LIMITATION OF THE STUDY

TIME CONSTRAINTS: One the challenges experienced by the researcher is the issue of time; the research will simultaneously engage in departmental activities like seminars and attendance to lectures. But the researcher was able to meet up with the deadline for the submission of the project.

FINANCIAL CONSTRAINTS: Every research work needs funding; however lack of adequate funds might affect the speed of the researcher in getting materials for completion of the project.

1.9 DEFINITION OF TERMS

Eucalyptus

Fast-growing evergreen Australasian tree that has been widely introduced elsewhere. It is valued for its timber, oil, gum, resin, and as an ornamental tree.

Phytochemical analysis

It refers to the extraction, screening and identification of the medicinally active substances found in plants. Some of the bioactive substances that can be derived from plants are flavonoids, alkaloids, carotenoids, tannin, antioxidants and phenolic compounds.

Antimicrobial activity

Antimicrobial activity can be defined as a collective term for all active principles (agents) that inhibit the growth of bacteria, prevent the formation of microbial colonies, and may destroy microorganisms.

Eucalyptus citriodora

Similar to but smaller than the spotted gum and having lemon-scented leaves

Microbroth dilution method