Introduction 1 TRADITIONAL MEDICINES Medicinal plants have played a vital role in nature as a repository of treasures, since times immemorial. Ample of notable modern medicines that have been sequestered in nature, originate from plants (Cowan, 1999). Plant materials have always been an important source to contend many serious diseases all over the world in conventional medical systems and provide solutions for health related issues in developing countries. The human body has a definite physiological reaction when it intakes chemical substances or group of compounds obtained from medicinal plants. These chemical compounds are known as secondary metabolites (Edeoga et al., 2005). In plants, these phytochemicals are classified into two broad categories according to their function in the metabolism process, viz., primary metabolites and secondary metabolites. Phytochemicals or phytoconstituents or plant secondary metabolites are all synonyms. Phytoconstituents are responsible for pharmaceutical activities in plants (Savithramma et al. , 2011). Primary metabolites are necessary to fulfill all metabolic activities which directly regulate growth, nutrition and development process in plants but secondary metabolites do not play a direct role in growth, nutrition and reproduction but have other roles such as allelopathic interactions and protection from herbivory. Primary metabolites include simple carbohydrates, lipids, amino acids , proteins, all types of vitamins and chlorophylls while in secondary metabolites we include alkaloids, flavonoids, tannins, antraquinones, phytosteroids, saponins and others (Parekh and Chanda, 2008; Kumar et al. , 2009). To resist and alleviate diverse diseases secondary metabolites are acknowledged suitably and are abundant in medicinal plants. At global level, many vigorous and strong drugs have been extracted from herbal sources. Approx. 35,000 varieties of plants are used for medicinal purposes. It is a popular belief that the traditional medicines also known as Green medicines, are much safer, simply available and have very less after effects (Savithramma et al. , 2011). Herbal plants are pioneers for novel drug findings and many phytoconstituents are directly used as starting components for the formation of medicinally active components and some Introduction 2 are directly used as therapeutic agents. Human being have utilised these plant based medicines in various forms like powder, mixture of more than two plant extracts or in liquid form. The concept of Herbal medicines was very much popular in India and over the whole world and the utilization of herbal medicines has increased tremendously in last few 20- 25 years (Rios and Recio, 2005). Traditional herbal medicines are employed as crude drugs throughout the world within their own designed medical systems for e.g. in Asia, China follows Traditional Chinese medicine (TCM), Korea follows Korean Chinese medicine, Japan follows Japanese Chinese medicine also known as Kampo, Indonesia follows Jamu and India follows Ayurveda. In Europe, this system is followed as Phytotherapy and Homeopathy. In America, these systems are named as alternative medicinal systems where they combine with different herbal therapies to cure some serious ailments. Integrative medicine (Western medicine) has come in existence due to combination of Traditional medicines with Modern medicine (Feher and Schmidt, 2003; Piggott and Karuso, 2004; Clardy and Walsh, 2004; Koehn and Carter, 2005; Lee et al ., 2001). TRADITIONAL v/s MODERN MEDICINES Western medicine is a very popular form of medicine in the present time, but simultaneously, this system has also created problems in the form of some side- effects like carcinogenicity caused by the synthetic drugs. So, Phytotherapy is considered as the best alternative tool to alleviate the side- effects of synthetic drugs (Sanchez-Lamar et al., 1999).The plant based medicines which are used to combat various diseases are considered under separate branch of science called as herbal medicines or botanical medicines or Phytomedicines. After many years, another word emerged which replaced the word herbal medicine or Phytomedicine with Phytotherapy. The twentieth century healthcare system was totally dependent on natural drugs obtained from plant origin but gradually these natural drugs loss their popularity. Later on Phytotherapy was completely taken over by the allopathic system of treatment in which people sought immediate therapeutic effects of synthetic medicines without knowing their future side effects (Singh, 2007). Introduction 3 A person who deals with the formation of plant based medicines is called chemist of natural products or Phytochemist. Plant material is first identified, collected by Phytochemist and further subjected to purification process. Different parts of the plants are subjected to form crude extract in which all phytochemicals are equally present. The crude extract of the various plant parts is tested against selected biological agents and active phytochemicals are isolated and further characterized by specific techniques. This whole protocol is known as bioassay- guided fractionation. So, without the knowledge of molecular biology, it would be very much difficult to discover a novel drug from medicinal plants. Pharmacognosy is an interdisciplinary approach which encloses many suitable fields of science. The term Pharmacognosy has been utilized and practiced by Phytochemists, since 18 th century, to formulate many crude medicines (Samuelsson, 2004; Kinghorn, 2001). A detailed definition according to the American Society of Pharmacognosy defines it as ‘‘the study of the physical, chemical, biochemical and biological properties of drugs, drug substances, or potential drugs or drug substances of natural origin as well as the search for new drugs from natural sources’’. Pharmacognosy includes the current research on drugs obtained through not only the medicinal plants but it also incorporate all kinds of unicellular as well as multicellular organisms like bacteria, algae, fungi, plants, animals and aquatic organisms. In broader sense, Pharmacognosy is the study of a number of criterions of herbal dietary additives and medicines which may be further tested by Food and Drug Administration (FDA) to design approved medicines (Cardellina, 2002; Tyler, 1999). According to Bruhn and Bohlin, pharmacognosy can be stated as ‘‘a molecular science that explores naturally occurring structure– activity relationships with a drug potential’’ (Bruhn and Bohlin, 1997). People are again focusing on herbal products because of increasing side effect of these synthetic drugs. In recent times, the whole world is turning towards natural products from artificial synthesized products and it is very well known that medicinal plants with their various therapeutic components aid to provide protection from diseases and disorders (Sharma et al . 2008). The early man was dependent on Introduction 4 these plants for seeking instant relief from critical ailments and pain which also helped them to survive long with enduring health (Nair and Chanda, 2007). A survey of top-selling medicines conducted in 2001-2002 shows that approximately 25% drugs are natural compounds or procured from plants (Butler, 2004). World Health Organization (WHO) also published a list of 252 medicines of which 11% are solely plant based. It has also been concluded by WHO that 65–80% of world’s population is still dependent on herbal medicines for major health related issues (Rates, 2001; Arora et al. , 1999; Savithramma et al ., 1996). The number of drugs that have been isolated from plants indicates their activity against broad range diseases (Fabricant and Farnsworth, 2001). All plants have some unique properties and at the same time it has also been reported in different tribal areas or countries that an individual plant may also be utilized for different purpose. This indicates that plants tremendously have a wide range of healing powers because of their chemical composition (De Silva, 1997). In the present scenario, pharmaceutical industries are trying to focus on plant based medicines and research is continuously going on in the field of exploration of new medicinal plants. This is due to the increasing demand of herbal products which have lesser side effects as in contrast to other medicinal combinations (Pandey et al ., 2008). In drug making industries, adulteration and substitution has also exponentially increased & this is another reason why people are returning towards nature. Almost every third plant and its parts are accounted in for discovering conventional drugs in India. In Vedas also, which highlights the glorious Indian history of herbal drugs, plants are referred to as alleviative agents (Jayabalan et al ., 2011). Now days, many new phytoconstituents have been broadly interrogated as medicinal agents which were earlier not reported to have any pharmacological activity (Krishnaraju et al ., 2005). All natural products obtained from plants are also a novel source of antimicrobial drugs (Ahmad and Aqil, 2007; Barbour et al. , 2004). Over the world, a large number of medicinal plants are analysed for their antimicrobial potential but few of them have been systematically studied (Arora et Introduction 5 al. , 2009; Rojas et al., 2006). A host of infectious diseases can be treated with the help of these antimicrobial agents (Iwu et al ., 1999). Many scientists have been trying to isolate pure compounds which are pharmaceutically more active. Such kinds of compounds