**Abstract**

Drug discovery using natural products is a challenging task for designing new leads. It describe the bioactive compounds derived from natural resources, its phytochemical analysis, characterization and pharmacological investigation. It focuses on the success of these resources in the process of finding and discovering new and effective drug compounds that can be useful for human resources. From many years, natural products have been acting as a source of therapeutic agents and have shown beneficial uses. Only natural product drug discovery plays an important role to develop the scientific evidence of these natural resources. Research in drug discovery needs to develop robust and viable lead molecules, which step forward from a screening hit to a drug candidate through structural elucidation and structure identification through GC–MS, NMR, IR, HPLC, and HPTLC. The development of new technologies has revolutionized the screening of natural products in discovering new drugs. Utilizing these technologies gives us an opportunity to perform research in screening new molecules using a software and database to establish natural products as a major source for drug discovery. It finally leads to lead structure discovery. Powerful new technologies are revolutionizing natural herbal drug discovery.

**Keywords:** natural products, herbal, drug discovery, phytochemicals, bioactive

### **1. Introduction**

Natural products and traditional medicines are of great importance. Natural products and their derivatives have been recognized for many years as a source of therapeutic agents and structural diversity. Natural products have a wide range of diversity of multidimensional chemical structures; in the meantime, the utility of natural products as biological function modifiers has also won considerable attention [1].

Drug discovery is leading to be a challenging scientific task to find robust and viable lead candidates, which is nothing but the process flow from a screening of natural product to a new isolate that requires expertise and experience. However, in addition to their chemical structure diversity and their biodiversity, the development of new technologies has revolutionized the screening of natural products in discovering new drugs [2]. Applying these technologies offers a unique opportunity to reestablish natural products as a major source for drug discovery. The present

article attempts to describe the process of isolation, characterization, and utilization of bioactive compounds derived from natural products as drug candidates called as lead, which focus on the success of pharmacological activity in the process of finding new and effective drug compounds; this process is commonly referred to as "natural product in drug discovery."

Natural products played a vital role on this earth, so man's existence has been made possible. The outstanding phenomenon of nature always stands as golden mark for achieving the herbal drug discovery [3].

From earlier decades medicinal plants existed on earth. Thus, medicinal herbs are of global and paramount importance. The world is decorated with medicinal herbs, which is a rich wealth of endurance. Every plant is identified by its own different therapeutic properties due to active bioactive molecule. In the modern system of medicine, natural drug substances are reported to be vital and have appreciable roles. Their therapeutic role was justified by the presence of their bioactive molecules. Due to disease-inhibiting capabilities, they are extremely useful as natural drugs, provide basic bioactive compounds that are less toxic and more effective, and bring biological and chemical means of modification and extraction of natural products into potent drug.

The raw materials for Ayurvedic medicines were mostly obtained from plant sources in the form of crude drugs such as dried herbal powders or their extracts or mixture of products. Apart from these systems, there has been a rich heritage of ethnobotanical usage of herbs by various colorful tribal communities in the country [4].

It has been estimated that nearly 75,000 species of higher plants exist on the earth, and only 10% have been used in traditional medicine. Only 1 to 5% have been studied scientifically and are known to have therapeutic value [5].

Around the globe, herbal medicine is based on traditional medicine. As per the oral survey made in many regions of the world, it has been said that traditional medicines have their own importance and basic philosophy. So exploration of the chemical constituents of the plants and their pharmacological screening may provide us the basis for developing a lead molecule through herbal drug discovery. The very important life-saving drugs have been provided by herbs in modern medicine. But among the estimated 4-lakh plant species, only 6% have been studied for their activity and very less not more than of 20% have been investigated phytochemically [6]. Thus, there is a need of investigating the various bioactive fractions and the phytoanalysis and phytopharmacological evaluation of herbal drugs for achieving the dreams of herbal drug discovery.

 Working role of every green herbal drugs from plant source and synthesis of bioactive products in their own way as God's gift and preserve them within which are extractable and used raw material as and when required through various scientific process for various scientific investigations and study of herbal drug discovery. Many pharmaceutical compounds contain secondary metabolites of plants that are of vital importance in drug designing. However, in order to have a good supply of the source material, some factors like environmental changes, diverse geographical distribution, labor cost, and selection of the superior plant should be taken care of by green plant developers so that good plants will be beneficial to pharmaceutical industry to develop good-quality herbal drugs [7].

 Natural products have played, and will continue to play, a key role in drug discovery and are therefore traditionally claimed as the cornerstones of drug discovery and development. Many drugs that are available in market today were discovered from natural sources [8]. An important example is the analgesic activity of aspirin [22],

which is so far the world's best known and most universally used medicinal agent. Its origin is from the plant genera *Salix* spp. and *Populus* spp. and it is related to salicin. A good example is serendipitous discovery of the antibiotic penicillin [22] in the laboratory from the fungus *Penicillium notatum.* 

 Many other examples show the value and importance of natural products from plants and microorganisms in modern days. Paclitaxel (Taxol [22]), which was first isolated from the bark of the Pacific yew tree *Taxus brevifolia* (Taxaceae), is the most recent example of an important natural product that has made an impact in medicine. Activity against a variety of retroviruses, including HIV, two compounds isolated from *Hypericum perforatum* (Guttiferae) are hypericin and pseudohypericin. They are of paramount importance due to inhibition of release of reverse transcriptase by stabilizing the structure of the HIV capsid and thus preventing the uncoating process [9, 10].

In four different ways, medicinal plants having good therapeutic properties are valuable for modern system of herbal and natural drug discovery.


#### **Figure 1.**  *Various strategies for the discovery of drugs from natural resources.*


Various strategies for the discovery of drugs from natural resources can be seen in **Figure 1**.
