The “Yin” and “Yang” of Target-Oriented Anticancer Phytochemicals Derived from Herbal Medicines

Contemporary chemotherapy has encountered many challenges including variable treatment outcomes and low therapeutic index of conventional cytotoxic drugs. There is an increasing trend to explore effective medicinal herbal products and the phytochemicals derived from them that have the potential to be developed as useful therapeutic adjuvants. Alternatively, concerns have also been raised regarding the lack of scientific evidence on action mechanisms and possibility of herb–drug interactions with the increased use of anticancer herbal medicinal compounds. The present review attempts to provide information to account for both positive (Yang) and negative (Yin) sides of the use of herbal medicinal products and their active constituents in daily clinical practice as well as the advancement of experimental works in target-oriented anticancer treatment. This chapter begins with a few examples of typical herb–drug interactions and to suggest several ways to prevent these from happening in future practice. Following this, the benefits of using herbal medicinal agents and the concepts behind will be introduced, allowing readers to envisage the rationale and potential of developing active phytochemicals as effective and well-tolerated chemotherapeutics in modern treatment approach of human cancers. The discovery of a series of anticancer herbal medicinal agents in the last 10 years that undergo precise mechanisms of action with known molecular targets will be discussed in details. The knowledge acquired during the identification and investigation of these potential herbal medicinal compounds could help oncologists to establish effective and safer chemotherapeutic adjuvants in the treatment of human cancers.