Biological and Phytochemical Screening of Plants

Camptothecin and taxol are secondary metabolites found, respectively, in the wood bark of Camptotheca acuminata , a native of China, and Taxus brevifolia , found in the northwest Pacific coastal region of the United States. The compounds were isolated guided by bioassay on various extracts and chromatographic fractions. Their unique and hitherto unknown structures were elucidated by nuclear magnetic resonance, mass spectrometry, and X-ray analysis. Both compounds have unique mechanisms of antitumor activity; camptothecin uniquely inhibits an enzyme, topoisomerase I, involved in DNA replication. Taxol binds to a protein, tubulin, thus inhibiting cell division. Taxol has been called the best new anticancer agent developed from natural products, showing particular efficacy against ovarian cancer. Camptothecin and analogues singly or combined with cisplatin show efficacy against solid tumors, breast, lung, and colorectal, which hitherto have been unaffected by most cancer chemotherapeutic agents.

https://cancerres.aacrjournals.org/content/canres/55/4/753.full.pdf

Camptothecin and Taxol: Discovery to Clinic—Thirteenth Bruce F. Cain Memorial Award Lecture

Ruminant animals have two metabolic systems that differ in their nutrient requirements: microbial metabolism in the rumen and mammalian metabolism in the tissues. Maximizing or optimizing ruminant productivity involves meeting requirements in proper amounts and balance for both metabolic systems. Ruminant nutritionists formulate diets with an intention of providing the animal with optimal levels of nutrients to achieve the optimal or maximal level of performance. Ideally, most of the dietary constituents should be digested, absorbed and utilized by the tissues as completely as possible. However, in reality, feed components are digested incompletely, more so with feedstuffs fed to ruminants than to non-ruminants. In ruminants, nutrient inputs are subjected first to fermentative digestion by microorganisms and then to glandular digestion by the host. Fermentative digestion is advantageous for substrates that cannot be digested by the host enzymes but is inefficient for digesting proteins, amino acids and sugars, because of losses in energy and nitrogen. Therefore, a proper balance between fermentative and glandular digestion needs to be achieved for optimal productivity.

Manipulation of ruminal fermentation

Camptothecin (CPT) is a pentacyclic alkaloid isolated from wood and bark of Camptotheca acuminata. Initially it was found to be highly active in a number of mouse in vivo cancer assays. Subsequently, CPT was found to uniquely inhibit an enzyme, topoisomerase I, which is involved in DNA replication. A number of CPT analogs are in advanced clinical trial, and two, Topotecan and CPT-11, have been approved for marketing by the FDA. taxol, a taxane alkaloid, was isolated from Taxus brevifolia. Taxol is a highly cytotoxic compound active in several mouse antitumor assays. It was subsequently found to uniquely inhibit tubulin, a protein involved in mitosis. After clinical evaluation, it has become the drug of choice for treatment of ovarian cancer.

Camptothecin and taxol: discovery to clinic

Camptothecin and taxol: from discovery to clinic

This is a report of the chemical examination of the fourth 1,000 accessions in a survey of plants for steroidal sapogenins and is thus a continuation of the reports on the first three 1,000 accessions (1-6). Data are given for 950 samples, representing 100 families, 272 genera, and 432 identified species. Of these, 14 families, 151 genera, and 376 species are new in this series. Quantitative data are given for the occurrence of 15 steroidal sapogenins, of which two, gentrogenin and correllogenin, are new. Qualitative data are given for the occurrence of these groups of constituents: saponins, flavonoids, alkaloids, tannins, and unsaturated sterols. There is no previously published chemical information on about 50 per cent of the species examined.

Steroidal sapogenins. XXV. Survey of plants for steroidal sapogenins and other constituents.

Scientific EditionSteroidal Sapogenins XLIII. Survey of Plants for Steroidal Sapogenins and Other Constituents

Two new isomeric 12-ketonic sapogenins have been isolated from tubers of Dioscorea spiculiflora , obtained in Chiapas province, Mexico. The new sapogenins, called gentrogenin and corellogenin, constitute 20 to 55 per cent of the total sapogenin content which ranges from 2.0 to 5.5 per cent, moisture free basis. Methods for the analysis and isolation of gentrogenin and correllogenin are presented in detail. The more important physical constants including melting point, optical rotation, and infrared spectra are recorded.

H.S. Gentry

Papers

Steroidal sapogenins. XXV. Survey of plants for steroidal sapogenins and other constituents.

Scientific EditionSteroidal Sapogenins XLIII. Survey of Plants for Steroidal Sapogenins and Other Constituents

Steroidal sapogenins XXXIX.: Occurrence and Isolation of Gentrogenin and Correllogenin from Dioscorea spiculiflora