J.J. Willaman

Bio: J.J. Willaman is an academic researcher from United States Department of Agriculture. The author has contributed to research in topics: Sapogenin & Paper chromatography. The author has an hindex of 8, co-authored 11 publications receiving 241 citations.

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

Abstract: 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.

Alkaloid hunting

Abstract: About 950 alkaloids have been isolated and named from the two percent ot all species which have been tested tor them. As a ǵuide in further search for alkaloids, their presence in and absence from some 250 families of plants are here tabulated.

Steroidal Sapogenins LV

Abstract: This report covers the fifth 1,000 accessions in a survey of plants for steroidal sapogenins and is thus a continuation of the previous four reports (1–7). Data are given for 990 accessions (all but 107 from the United States), representing 147 families, 547 genera, and 921 species. Few steroidal sapogenins were found, largely because of the absence of Agave, Yucca , and Dioscorea; but alkaloids were qualitatively identified in 86 species, 45 of which are new to the record.

Strategies in herbivory by mammals: the role of

Abstract: Large herbivores must select food from a wide variety of plant parts, species, and strains. These differ in nutritional value (protein, carbohydrate, etc.), toughness, spinosity, etc. Even greater differences are found in types and concentrations of secondary compounds. Every plant produces its own set of secondary chemical compounds, which to a great extent are unique to it or its species. Ingestion of natural concentrations of these compounds can lead to either death or severe physiological impairment. The ubiquitous nature of these compounds would make herbivory impossible unless animals had mechanisms for degrading and excreting them. An animal displaying no obvious symptoms of poisoning is not free of the problem of ridding itself of toxic compounds; if it is eating plants, it almost certainly has this problem. Herbivores are capable of detoxifying and eliminating secondary compounds. Limitations of these mechanisms force mammalian herbivores to consume a variety of plant foods at any one time, to treat new foods with caution, to ingest small amounts on the first encounter, and to sample food continuously. Selection of foods is based on learning in response to adverse internal physiological effects, and herbivores probably cannot predict these from the smell or taste of new foods. Herbivores prefer to eat familiar foods and can seek out and consume foods that rectify specific nutritional deficiencies induced by detoxification. They should prefer to feed on foods that contain small amounts of secondary compounds, and their body size and searching strategies should be adapted to optimize the number of types of foods available with respect to the total amount of food that can be eaten and will be present in the future. Natural selection can increase the efficiency of degrading particular secondary compounds. Specialist herbivores, like koala and mountain viscacha, are expected where a large amount of several related toxic foods is present in a year-round supply. However, few large herbivores are specialized on such a restricted range of foods.

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

Abstract: 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.

Manipulation of ruminal fermentation

Abstract: 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.

Camptothecin and taxol: discovery to clinic

Abstract: 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.