Since prehistoric times, human has utilised the environment for his survival. They have relied on natural products to improve their health or to cure illness. Even till the dawn of this century, the therapeutic properties of a large number of plants are being recognised through research and documented. This growing scientific and commercial interest in medicinal plants is due to the great economic potential and cultural acceptability of plant-based products. Natural sources such as plants provide a large variety of bioactive compounds with structural diversity which can be used as pharmacophores with a definite physiological action on the body for treating and preventing diseases. These bioactive compounds in plants are compounds produced by plants having pharmacological or toxicological effects in man and animals (Bernhoft, 2010).
Sigesbeckia orientalis is a weed growing in hot climates from the Asteraceae or Compositae family and it is among one of the numerous plants that have been used traditionally for the treatment of a range of ailments in different countries. Weeds are important source of medicines for indigenous people and are easily available throughout the world, as per Singh et al., (2012), they are generally non-cultivated; they can however possess more potent and a greater variety of medicinal properties than other medicinal plants. The physiological activities shown by medicinal plants are due to the presence of different classes of bioactive constituents, the most important of which are alkaloids, tannins, flavonoids, terpenoids, steroids and phenolics compounds. The isolation and characterization of the bioactive compounds are important in order to determine the pharmacological activities of the various individual bioactive constituents from each plant as well the synergistic effect of these compounds from the plant extract.
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With the emergence of clinical resistance of microorganisms to the currently available antibiotics, the search for novel compounds with antibiotic properties is ongoing; as such weeds can be screened for anti-bacterial activities which can be used to counteract the growth of antibiotics-resistant bacteria presently and in the future. Diabetes, worldâ€™s largest endocrine disease is characterised by a rise in fasting blood glucose level (Mahomodally, 2012), there is a continuing search for compounds with anti-diabetic potential since the currently available therapy is not completely effective in lowering the blood glucose level in diabetic patients to the normal range. Natural products therefore serve as an appropriate reservoir to search for compounds with new structural configuration for greater anti-diabetic potency and lower side effects.
ROS and RNS are detrimental to health when found in the body in excess amount while they serve as important factors for proper functioning of the physiological system when present at low concentration. High concentration of ROS and RNS in the body leads to oxidative stress which can give rise to many diseases including heart failure, atherosclerosis and aging amongst others. The oxidative stress can be combated by endogenous bodyâ€™s antioxidant mechanism as well as by exogenous anti-oxidants found in food, however, the anti-oxidant activity is not sufficient and some exogenous anti-oxidants present with harmful secondary effect. Since plants produce antioxidants to manage the oxidative stress due to sun and oxygen (Biswas and Bhattacharya, 2012), they represent a source of new and more effective anti-oxidants with reduced secondary effects. Plants have also proved to be a good source of compounds with anti-acetylcholinesterase activity (Bakthir et al., 2011) which is useful in the management of Alzheimerâ€™s disease. This study therefore aims at screening phytochemicals present in the weed S.orientalis and to characterise the pharmacological importance of this weed in managing diabetes, decreasing oxidative stress, fighting infections caused by bacteria and in the treatment of Alzheimerâ€™s disease.
AIM AND OBJECTIVES
To study the bioactive compounds from the weed Sigesbeckia orientalis Linn.
To carry out extraction of the leaf, stem, root and flower part of S.orientalis using water, methanol, ethyl acetate and dichloromethane as solvent.
To determine the phytochemicals present in the different extracts of S.orientalis.
To quantify the total phenolics and total flavonoids content of the different extracts of S.orientalis.
To evaluate the anti-oxidant properties of different extracts of S.orientalis by assessing the in vitro DPPH scavenging potential, the iron metal chelating activity and Catalase activity of the all the extracts.
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To determine whether the anti-diabetic properties of S.orientalis is through the inhibitory effects on the enzyme alpha-amylase.
To find out whether the extracts of S.orientalis have acetylcholinesterase inhibitory activity
To evaluate the potential of the S.orientalis extracts to inhibit the growth of two bacteria: Staphylococcus aureus and Escherichia coli.
Sigesbeckia orientalis had long been used as folk medicines in the Asian countries and the whole plant is part of the Mauritian traditional medicine in the management of ailments like infections, fever and diabetes. While the traditional use against microbial infections has been well documented, the weed lack scientific studies on the bioactive constituents present in the different parts of this plant, this study therefore reveal the phytochemicals present in the leaves, root, stem and flower of S.orientalis. Limited studies have been carried to assess the anti-oxidant and anti-diabetic properties of S.orientalis, this study will further shed light on the anti-oxidant potential of the different parts of the whole plant. Till date the mechanisms through which the weed S.orientalis mediates its anti-diabetic activity have not been documented, this study determines whether the anti-diabetic effects of the weed are through the enzyme alpha-amylase inhibition pathway. Another novelty in this study is the investigation of the anti-acetylcholinesterase activity of all the parts of the plant S. orientalis, upon which no study has been carried out till present.
Determination of the therapeutic effectiveness of the weed S.orientalis will provide a greater range of remedies for the different ailments that it can manage. Emergence of antibiotic resistant bacteria calls for an ongoing search for natural products with antibacterial properties. The number of people suffering from diabetes is on rise, as such, searching for natural products with effective anti-diabetic properties will help to control this rise and manage the disease in those who have attained it. Investigation of the biological activities of the plant S.orientalis will provide the population of developing countries greater access to remedies for different ailments at a lower cost and probably with fewer side effects.