Plants have been a major source of anti-cancer agents, with many clinically useful drugs derived from natural sources. These include vinblastine, vincristine, camptothecin derivatives, topotecan, irinotecan, etoposide, paclitaxel (taxol), and combretastatin A4 phosphate. Over 60% of current anti-cancer agents are derived from natural sources, including plants, marine organisms, and microorganisms. The search for anti-cancer agents from plants began in the 1950s with the discovery of vinca alkaloids and podophyllotoxins, leading to the NCI's plant collection program in the 1960s. This program led to the discovery of taxanes and camptothecins, which took about 30 years to develop into clinically active agents. The plant collection program was terminated in 1982, but new screening technologies led to the revival of plant collections in 1986, focusing on tropical and subtropical regions. Several plant-derived agents are in clinical use, including vinca alkaloids, etoposide, teniposide, paclitaxel, and camptothecin derivatives. These agents are used to treat various cancers, including leukemias, lymphomas, and solid tumors. Other agents in clinical development include flavopiridol, combretastatins, roscovitine, and maytansine derivatives. These agents are being tested for their efficacy against a range of cancers, including breast, ovarian, and prostate cancers. Plant-derived agents in preclinical development include compounds such as betulinic acid, indirubins, and triterpenoid acids. These compounds show promise in inhibiting cancer cell growth and have been tested in animal models. The resistance of cancer cells to treatment with standard anti-cancer agents is a significant challenge, and research is ongoing to develop more effective drugs. The identification of molecular targets associated with cancer has led to the development of new anti-cancer agents through high-throughput screening. These agents are being tested for their ability to inhibit key proteins involved in cell cycle progression, such as cyclin-dependent kinases. The ability to target these proteins with natural products is a promising area of research, as it allows for the development of more effective and selective anti-cancer agents.Plants have been a major source of anti-cancer agents, with many clinically useful drugs derived from natural sources. These include vinblastine, vincristine, camptothecin derivatives, topotecan, irinotecan, etoposide, paclitaxel (taxol), and combretastatin A4 phosphate. Over 60% of current anti-cancer agents are derived from natural sources, including plants, marine organisms, and microorganisms. The search for anti-cancer agents from plants began in the 1950s with the discovery of vinca alkaloids and podophyllotoxins, leading to the NCI's plant collection program in the 1960s. This program led to the discovery of taxanes and camptothecins, which took about 30 years to develop into clinically active agents. The plant collection program was terminated in 1982, but new screening technologies led to the revival of plant collections in 1986, focusing on tropical and subtropical regions. Several plant-derived agents are in clinical use, including vinca alkaloids, etoposide, teniposide, paclitaxel, and camptothecin derivatives. These agents are used to treat various cancers, including leukemias, lymphomas, and solid tumors. Other agents in clinical development include flavopiridol, combretastatins, roscovitine, and maytansine derivatives. These agents are being tested for their efficacy against a range of cancers, including breast, ovarian, and prostate cancers. Plant-derived agents in preclinical development include compounds such as betulinic acid, indirubins, and triterpenoid acids. These compounds show promise in inhibiting cancer cell growth and have been tested in animal models. The resistance of cancer cells to treatment with standard anti-cancer agents is a significant challenge, and research is ongoing to develop more effective drugs. The identification of molecular targets associated with cancer has led to the development of new anti-cancer agents through high-throughput screening. These agents are being tested for their ability to inhibit key proteins involved in cell cycle progression, such as cyclin-dependent kinases. The ability to target these proteins with natural products is a promising area of research, as it allows for the development of more effective and selective anti-cancer agents.