ABSTRACT
Cancer is the most devastating disease with more than 10 million new cases every year around the world. It is well known that environmental factors and chemical carcinogens play a predominant role in the induction of DNA lesions and other genomic abnormalities which causes the cancer. Currently, several chemotherapeutic agents are being used in the treatment of cancer, including alkylating agents, antimetabolites antagonists, anticancer antibiotics, and plant-derived anticancer agents. However, chemotherapy, being a major treatment method used for the control of advanced stages of malignancies and metastasis, is known to exhibits severe toxicity (Markowitz and Bertagnolli, 2009). Because of high death rate associated with cancer and because of the serious side effects of chemotherapy and radiation therapy, many cancer patients seek alternative and/or complementary methods of treatment. Phytochemicals are one of fast growing anticancer agents for such alternative therapies. Basically, phytochemicals are large variety of plant-derived chemical compounds, which are present in fruits and vegetables that may reduce the risk of cancer, possibly due to dietary fibers, polyphenol antioxidants, and anti-inflammatory effects. There are many plant-derived phytochemicals which have been used as anticancer drugs and it has been shown to inhibit cancer cell growth efficiently. Moreover, they are known to maintain the health and vitality of individuals, and also cure different diseases, without causing toxicity (Chung et al., 1995; Tyagi et al., 2010). More than 50% of all modern drugs in clinical use are of natural products, many of which have the ability to control cancer cells (Chao et al., 2005). A recent survey showed that more than 60% of cancer patients use vitamins or herbs as therapy. Interestingly, an important and well known cancer drug, Taxol (paclitaxel), is a phytochemical, initially extracted and purified from the Pacific yew tree (Taxus brevifolia) (Tyagi et al., 2010). Pharmacologically safe phytochemicals that have been identified from plants or their variant forms can modulate these molecular targets. These phytochemicals include genistein, resveratrol, dially sulfide, S-ally cysteine, allicin, lycopene, capsaicin, curcumin, 6-gingerol, ellagic acid, ursolic acid, betulinic acid, flavopiridol, silymarin, anethol, catechins and eugenol (Aggarwal et al., 2004). Because of their pharmacological safety, these agents can be used alone to prevent cancer and in combination with chemotherapy to treat cancer. These herbal medicines have been increasingly accepted universally, and they have an impact on both world health and international trade (Park et al., 1998). The
plant-based traditional medicines are widely used in India and China. Very recently, for alternative therapy, National Centre for Complementary and Alternative Medicine has been established in USA. The herbal products have been classified under “dietary supplements” and are included with vitamins, minerals, amino acids, and “other products intended to supplement the diet”. The National Cancer Institute collected about 35,000 plant samples from 20 countries and has screened around 114,000 extracts for anticancer activity. Of the 92 anticancer drugs commercially available prior to 1983 in the US and among worldwide approved anticancer drugs between 1983 and 1994, 60% are of natural origin. In this instance, natural origin is defined as natural products, derivatives of natural products, or synthetic pharmaceuticals based on natural product models (Cragg and Newman, 1997). Other important phytochemicals such as Allium sativum, Actinidia chinensis, Aloe vera, Ananas comosus, Angelica sinensis, Annona species, Arctium lappa, Astragalus membranaceus, Betula utilis, Catharanthus roseus, Chlorella pyrenoidosa, Colchicum luteum, Combretum caffrum, Curcuma longa, Echinacea angustifolia, Fagopyrum esculentum, Glycine max, Glycyrrhiza glabra, Gyrophora esculenta, Lentinus edodes, Panax ginseng, Linum usitatissimum, Picrorrhiza kurroa, Mentha species, Podophyllum, and Withania somnifer are known to control the growth of cancer cells (Sakarkar and Deshmukh, 2011). In this article, we aim to provide an overview the recent advances in the research based on phytochemicals for cancer therapy.
