**4. Drugs (medicine) discovered from natural sources and development**

The development of new drug is a complex, time-consuming, and expensive process (**Figure 1**). The time taken from discovery of a new drug to its reaching the clinic is approximately 12 years, involving more than 1 billion US dollars of investments in today's context [48]. Essentially, the new drug discovery involves the

**Figure 1.**  *Modern drug discovery and development processes from the medicinal plant [127].* 

#### *Pharmacognosy: Importance and Drawbacks DOI: http://dx.doi.org/10.5772/intechopen.82396*

identification of new chemical entities (NCEs), having the required characteristic of drug ability and medicinal chemistry. These NCEs can be sourced either through chemical synthesis or through isolation from natural products. Initial success stories in new drug discovery came from medicinal chemistry inventions, which led to the need of development of higher number of chemical libraries through combinatorial chemistry. This approach, however, was proven to be less effective in terms of overall success rate. The second source of NCEs for potential use as drug molecules has been the natural products. Before the advent of high throughput screening and the post genomic era, more than 80% of drug substances were purely natural products or were inspired by the molecules derived from natural sources (including semisynthetic analogs) [49]. There are various examples of development of new drugs from the plant sources. Morphine was isolated from opium produced from cut seed pods of the poppy plant (*Papaver somniferum*) approximately 200 years ago [50]. Pharmaceutical research expanded after the Second World War to include massive screening of microorganisms for new antibiotics, inspired by the discovery of penicillin [50]. Few drugs developed from natural sources have undoubtedly revolutionized medicine like antibiotics (e.g., penicillin, tetracycline, erythromycin), antiparasitics (e.g., avermectin), antimalarials (e.g., quinine, artemisinin), lipid control agents (e.g., lovastatin and analogs), immune-suppressants for organ transplants (e.g., cyclosporine, rapamycins), and anticancer drugs (e.g., paclitaxel, irinotecan) [51].

The WHO has estimated that the majority of the populations in Africa, Asia, and Latin America still use TM for their primary health care needs [52]. In industrialized countries, plant-based TM or phytotherapeuticals are often termed complementary or alternative medicine (CAM), and their use has increased steadily over the last 10 years [53]. In the USA alone, the total estimated "herbal" sale for 2005 was \$4.4 billion, a significant increase from \$2.5 billion in 1995 [54] while also accounting for an estimated 1 billion Malaysia ringgit annually [55]. However, such "botanical dietary supplements" are regulated as foods rather than drugs by the United States Food and Drug Administration (US FDA) [54].
