Antitumor plant product

Among them, ansamitocins P-3 (81) and P-4 (83) were the most abundant [126]. Reductive hydrolysis of each antibiotic with LiAlH at low temperature gave maytansinol (= ansamitocin P-0) (84). Acetylation of 84 with acetic anhydride in pyridine yielded an antitumor plant product maytanacine (ansamitocin P-1) (79). Maytansinol propionate, corresponding to ansamitocin P-2 (80), could be prepared by Ae acylation of 84. Isolation procedures, chemical characterization and the structures of 79 - 83 were described [127]. 

Taxol la is an antitumor plant diterpene isolated from the yew tree Taxus spp. in the late 1960s. It was named taxol at the time of its first isolation by Wani et al. In the 1990s, when Bristol-Myers Squibb (BMS) launched it on the market, Taxol was registered as an anticancer product, and Taxol was assigned a generic name, pacli-taxel. Both taxol and paclitaxel are referred to in this chapter to describe the same compound. 

In a blow to natural-products chemistry in the U.S., the Board of Scientific Counselors, Division of Cancer Treatment, National Cancer Institute, voted on October 2, 1981, to abolish the NCI research contract program concerned with the development of antitumor agents from plants. I fear this signals the end of significant government-sponsored research in the U.S. on medicinal plants, leaving the research to the pharmaceutical firms, who have shown relative disinterest in plant products. 

The results of an antitumor screen are summarized in Table 8.1. The attrition table summarizes the results from 338,072 samples tested against tumor cells derived from soft tissue sarcomas. Given that the samples included one combinatorial collection with approximately 1.5 million compounds and that each natural product extract most likely contained 100 or more, the total number of compounds tested in this screen exceeded 5 million. As shown in the first column of Table 8.1, the samples were from 11 collections composed of single synthetics, compounds synthesized by combinatorial chemistries, and purified natural products and extracts. The natural products were derived from microorganisms (actinomyces and fungi), plants, and marine invertebrates. 

The isolation of the antitumor agents vincaleukoblastine (1) and leuro-cristine (2) from Catharanthus roseus (L.) G. Don has proved to be one of the most important developments in both natural product chemistry and the clinical treatment of cancer during the 1960s to 1980s. More alkaloids (over 90) have been isolated from C. roseus than from any other plant, and because of the complexity of the alkaloid mixture this work has required the most advanced isolation and structure determination techniques. The exceptional interest in the broad spectrum of antitumor activity of these compounds has resulted in numerous achievements in the pharmaceutical, clinical pharmacologic, and therapeutical sciences. Simultaneously, strenuous efforts have been made in three areas of the natural product chemistry (i) elaboration of a practical semisynthesis of... 

On the other hand, EGCG and green tea extract are acknowledged cancer-preventive agents in Japan [75,76]. Natural products with antitumor promotion activity isolated from foodstuff and medicinal plants have been summarized by Konoshima and his co-worker and Akihisa and... 

In this proceeding we have described the preparation of 32 plant growth regulators, three diterpenes, and an ongong effect to synthesize a structurally complex antitumor agent. Only time will determine whether any of these natural products and their derivatives become important pharmaceutical agents. 

Highlights of Research on Plant-Derived Natural Products and Their Analogs with Antitumor, Anti-HIV, and Antifungal Activity ... 

BRMs isolated from plant tissues and bacterial products show nonspecific [65,66] and T cell-mediated antitumor effects [67,68]. Administration of these BRMs improves the quality of life, without causing complete regression of the cancer in most cases. The antitumor effect of the acidic glycoprotein in the tumor rechallenge system was at least comparable to that of OK-432 (Table 1). 

Plant-derived natural products with documented anticancer and antitumor properties can be classified into the following chemical groups (Kintzios and Barberaki, 2004) ... 

Some plants have been cultivated by germanium penetration into the plant from its roots and organogermanium pharmaceuticals have been prepared. Cultivation of Sac-charomyces cerevisiae or Ganoderma lucidum in carboxyethylgermanium sesquioxane medium gave a product with antitumor and interferon-inducting activity . 

As enantiomericaUy pure sulfoxides are excellent chiral auxUiaries for asymmetric synthesis, different approaches for biocatalytic asymmetric oxidations at the S-atom have been explored [30, 31]. Asymmetric peroxidaseorganic sulfides to sulfoxides in organic solvents opens up attractive opportunities by increased substrate solubility and diminished side reactions [32]. Plant peroxidases located in the cell wall are capable of oxidizing a broad range of structurally different substrates to products with antioxidant, antibacterial, antifungal, antiviral, and antitumor activities [33]. Hydroperoxides and their alcohols have been obtained in excellent e.e. in the biocatalytic kinetic resolution of secondary hydroperoxides with horseradish and Coprinus peroxidase [34]. 

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