Current Status of Commercial Anticancer Phytochemicals and Their Derivatives: Natural Anticancer Bioactive Compounds

Introduction

The pharmaceutical industry is always in search of new lead compounds. The main sources of these compounds have been the natural products from different sources that possess different pharmacological important properties. These compounds are very much beneficial for the maintenance of human health. The natural compounds such as aspirin, morphine, digitoxin, quinine and many more are the natural products that have been used for long time for the treatment of various diseases (Cragg et al., 2005). Cancer is one of the diseases which were initially thought as an incurable disease. It is a deadly disease that is characterised by the uncontrolled growth and division of the cells of a part of the body that have started invading the surrounding tissue and then ultimately to the whole body (Cancer Research UK, 2019). Theoretically, there are more than 200 types of cancer but the prominent ones are breast, colon, lungs and prostate cancer. Based on their activity and infection type, cancer has been classified into five classes of brain tumour, carcinoma, leukaemia, lymphoma and sarcoma (Gezici & Sekeroglu, 2019). It is estimated that the global cancer cases will be around 20 million in the next few years (Seca & Pinto, 2018). So the major challenge is the looking for the cancer treatment by investigating new effective anticancer drugs. The currently used treatments for the cancer are radiotherapy, chemotherapy, surgery, bone marrow transplant and using some anticancer drug. The most effective and successful chemotherapeutic and anticancer drugs used for the cancer treatment have been surprisingly natural in origin. The commercialised anticancer drugs can be classified into the synthetic (Chemically synthesised in laboratory), natural (obtained from the natural sources like plants, microbes, marine sources, etc.,), Natural product derivative (include all the semi synthetic analogues of natural products), and natural product mimic (compounds that are similar to natural compounds that are found in humans as the part of their process) (Newman & Cragg, 2020). In actual the most widely used anticancer drugs are either natural products or their analogues that are semi-synthetic in nature (Nahar & Sarkar, 2019). Natural compound shave been used as the basic molecule for the synthesis of analogues for the effective cancer treatment. In fact the natural products are also used to learn about the mechanism of action for the cancer treatment and he same is used for the synthesis of anticancer drugs by doing modifications at specific sites in the basic compounds. These days there is development of the synthetic analogues that are the compounds which mimics the natural compound that is very important for the cancer progression (Kinghorn et al., 2016). The natural products potential for the treatment of cancer was first obliged in 1950 by United States National Cancer Institute which then provided funds to carry out the research related to the identification of the anticancer compounds from the natural sources. After that numerous studies have been carried out to identify the potential anticancer drugs from different natural sources that could be used for the treatment of different cancers. Although initially only natural products were sued for the cancer treatment but with time there has been increase in the use of new approaches for the anticancer drug development that have now overshadowed the potential diversity among the natural products. Among different natural sources, the most widely used are the plants and marine organisms due to their sedentary lifestyle which means they will produce more secondary metabolites to protect themselves from the predators or parasites. This leads to the development of vast diversity among the compounds produced by these organisms as the part of their complex defence system (Williams et al., 1989). Thus these have been the source of many potential therapeutic drugs which have very high specific binding with the potent target (Paul, 1992).