Efforts in Bioprospecting Research: A Survey of Novel Anticancer Phytochemicals Reported in the Last Decade

Abstract

Bioprospecting natural products to find prominent agents for medical application is an area of scientific endeavor that has produced many clinically used bioactive compounds, including anticancer agents. These compounds come from plants, microorganisms, and marine life. They are so-called secondary metabolites that are important for a species to survive in the hostile environment of its respective ecosystem. The kingdom of Plantae has been an important source of traditional medicine in the past and is also enormously used today as an exquisite reservoir for detecting novel bioactive compounds that are potent against hard-to-treat maladies such as cancer. Cancer therapies, especially chemotherapies, are fraught with many factors that are difficult to manage, such as drug resistance, adverse side effects, less selectivity, complexity, etc. Here, we report the results of an exploration of the databases of PubMed, Science Direct, and Google Scholar for bioactive anticancer phytochemicals published between 2010 and 2020. Our report is restricted to new compounds with strong-to-moderate bioactivity potential for which mass spectroscopic structural data are available. Each of the phytochemicals reported in this review was assigned to chemical classes with peculiar anticancer properties. In our survey, we found anticancer phytochemicals that are reported to have selective toxicity against cancer cells, to sensitize MDR cancer cells, and to have multitarget effects in several signaling pathways. Surprisingly, many of these compounds have limited follow-up studies. Detailed investigations into the synthesis of more functional derivatives, chemical genetics, and the clinical relevance of these compounds are required to achieve safer chemotherapy.

Keywords: anticancer drugs; chemotherapy; natural products; phytochemicals.

Figure 1

Various phytochemical classes with examples of new members.

Figure 2

Chronological events that lead to cancer, explaining the relationship between abnormal cellular signaling pathway and cancer formation.

Figure 3

(A): Representative members of novel glycosides from various plant sources (compounds 1–7 and 12). Compounds 8–11 are cardenolide lactates isolated from Asclepias curassavica. (B): Representative members of novel glycosides from various plant sources (compounds 13 to 17).

Figure 4

Representative members of new polyphenolic phytochemicals from various plant sources (compounds 18 to 23).

Figure 5

(A): Representative members of new xanthone phytochemicals from various plant sources (compounds 24 to 35). (B): Representative members of new xanthone phytochemicals from various plant sources (compounds 36 to 42).

Figure 6

(A): Representative members of new terpenoid phytochemicals from various plant sources (compounds 43 to 57). (B): Representative members of new terpenoid phytochemicals from various plant sources (compounds 58 to 70). (C): Representative members of new terpenoid phytochemicals from various plant sources (compounds 71 to 81). (D): Representative members of new terpenoid phytochemicals from various plant sources (compounds 82 to 90).

Figure 6

(A): Representative members of new terpenoid phytochemicals from various plant sources (compounds 43 to 57). (B): Representative members of new terpenoid phytochemicals from various plant sources (compounds 58 to 70). (C): Representative members of new terpenoid phytochemicals from various plant sources (compounds 71 to 81). (D): Representative members of new terpenoid phytochemicals from various plant sources (compounds 82 to 90).

Figure 6

(A): Representative members of new terpenoid phytochemicals from various plant sources (compounds 43 to 57). (B): Representative members of new terpenoid phytochemicals from various plant sources (compounds 58 to 70). (C): Representative members of new terpenoid phytochemicals from various plant sources (compounds 71 to 81). (D): Representative members of new terpenoid phytochemicals from various plant sources (compounds 82 to 90).

Figure 7

Representative members of new alkaloid phytochemicals from various plant sources (compounds 91 to 100).

Figure 8

Representative members of new chalcone phytochemicals from various plant sources (compounds 101 to 103).

Figure 9

New phytochemicals belonging to different chemical classes. Polyenes, phytosterols, and a juglone analogue from various plant sources (compounds 104 to 109).