Exploring the biosynthesis of natural products and their inherent suitability for the rational design of desirable compounds through genetic engineering

Much effort has been invested in studying how natural products are biosynthesized, and great advances have been made in understanding how these compounds acquire their structural complexity and biological activities. In recent years, significant progress has been made due to the devoted efforts of scientists in this field and to technological advancements. Numerous details, applications, and innovative findings have been elucidated by scientists using biochemical, genetic, and molecular biological approaches. Here I present a comprehensive overview of highly valued biosynthetic proteins, polyketide synthase and nonribosomal peptide synthetase. I begin with "Diels-Alderase" a captivating enzyme that has the ability to catalyze a Diels-Alder reaction valued by chemists for its usefulness in chemical synthesis. A handful of these enzymes have been characterized and chemically authenticated. The most well understood enzyme of this category is macrophomate synthase. Secondly, I focus on the polyketide and nonribosomal peptide biosynthetic pathways and the enzyme assembly for producing its metabolite. Many important natural products are produced by this biosynthetic pathway as secondary metabolites, such as erythromycin, rifamycin, and FK520, as antibiotics and an immunosuppressive, respectively. I conclude with a discussion of nonribosomal peptides and their mechanistic pathways. Special attention will be devoted to de novo production of echinomycin in a heterologous manner, the earliest example of totally engineered biosynthesis of the biologically active form of a nonribosomal peptide host in Escherichia coli.     

长江中下游四大淡水湖生态系统完整性评价

长江中下游地区是我国淡水湖泊集中分布区域,研究该区域湖泊生态系统完整性对于湖泊生态系统保护和恢复具有重要意义。物理、化学和生物完整性指标已经广泛应用于河湖生态系统健康评价,但是缺少物理、化学和生物完整性的综合评价方法。以历史调查状况为主要参照系统,构建了基于物理、化学和生物完整性的多参数湖泊完整性综合评价指标体系,结合近年来长江中下游四大淡水湖(洞庭湖、鄱阳湖、巢湖、太湖)生态系统调查数据,对四大淡水湖生态系统完整性进行了评价。结果表明,洞庭湖、鄱阳湖、巢湖和太湖的综合得分分别为66、71、57和57。根据评价等级划分标准,洞庭湖和鄱阳湖生态系统完整性状况都达到"好"的等级,而巢湖和太湖则处于"一般"等级;结果显示,该指标能够表征人类活动对于湖泊生态系统完整性不同方面的干扰,且能够反映四大淡水湖生态系统完整性历史变化状况。因此,该方法可以作为长江中下游淡水湖泊生态系统完整性综合评价的工具并能够为湖泊生态系统的保护和恢复提供科学支撑。     

Biodiversity,bioactive natural products and biotechnological potential of plant-associated endophytic actinobacteria

Endophytic actinobacteria, which exist in the inner tissues of living plants, have attracted increasing attention among taxonomists, ecologists, agronomists, chemists and evolutionary biologists. Numerous studies have indicated that these prolific actinobacteria appear to have a capacity to produce an impressive array of secondary metabolites exhibiting a wide variety of biological activity, such as antibiotics, antitumor and anti-infection agents, plant growth promoters and enzymes, and may contribute to their host plants by promoting growth and enhancing their ability of withstanding the environmental stresses. These microorganisms may represent an underexplored reservoir of novel species of potential interest in the discovery of novel lead compounds and for exploitation in pharmaceutical, agriculture and industry. This review focuses on new findings in the isolation methods, bio- and chemical diversity of endophytic actinobacteria and reveals the potential biotechnological application. The facing problems and strategies for biodiversity research and bioactive natural products producing are also discussed.     

Detection and identification of mutagens and carcinogens as their adducts with guanosine derivatives

For use in screening for environmental mutagens and carcinogens, a highly fluorescent derivative of guanosine, 2'-deoxy-2'-(2",3"-dihydro-2",4"-diphenyl-2"-hydroxy-3"-oxo-1"-pyrrol yl) guanosine (FG), was synthesized. When incubated with FG in aqueous solution, mutagens form adducts that can be analyzed with an HPLC-fluorescence detector-system. By this method, mutagens such as glyoxal, methylglyoxal, 2-(2-furyl)-3-(5-nitrofuryl) acrylamide and 4-nitroquinoline-N-oxide, used as model compounds, were detected rapidly with high sensitivity. Reaction with isopropylideneguanosine (IPG), followed by isolation and characterization of the mutagen-IPG-adduct was found to be a useful method for identifying unknown mutagens in crude samples. This method was successfully applied in identification of the mutagens in heated glucose (200 degrees C, 20 min); glyoxal-IPG and 8-hydroxy-IPG were identified in the reaction mixture.     

Environmental carcinogenesis: an integrative model.

An integrative theory is proposed in which environmental carcinogenesis is viewed as a process by which the genetic control of cell division and differentiation is altered by carcinogens. In this theory, carcinogens include physical, chemical, and viral "mutagens," as well as chemical and viral gene modulators. Existing explanations of carcinogenesis can be considered either as somatic mutation theories or as epigenetic theories. Evidence seems to support the hypothesis that both mutations and epigenetic processes are components of carcinogenesis. The mutational basis of cancer is supported by the clonal nature of tumors, the mutagenicity of most carcinogens, high mutation frequencies in cells of cancer-prone human fibroblasts lacking DNA repair enzymes, the correlation of in vitro DNA damage and in vitro mutation and transformation frequencies with in vivo tumorigenesis, age-related incidences of various hereditary tumors, and the correlation between photoreactivation of DNA damage and the biological amelioration of UV-induced neoplasms. Since both mutagens and gene modulators can be carcinogenic it may be that carcinogens affect genes which control cell division. An integration of the mutation and epigenetic theories of cancer with the "two-stage" theory and Comings's general theory of carcinogenesis is proposed. This integrative theory postulates that carcinogens can affect regulatory genes which control a series of "transforming genes." A general hypothesis is advanced that involves a common mechanism of somatic mutagenesis via error-prone repair of DNA damage which links carcinogenesis, teratogenesis, atherosclerosis and aging. Various concepts are presented to provide a framework for evaluating the scientific, medical, and social implications of cancer.     

Environmental mutagenesis: Evolving strategies in the USA

A recent Environmental Mutagen Society report (the “Committee 17” report) made recommendations regarding the screening of environmental mutagens and the use of the resulting data. It is important in this respect to employ highly sensitive tests which detect heritable genetic damage of all possible molecular types. Mutagens of artificial origin which are being considered for continued production must be characterized with respect to their level and pattern of distribution and their persistence in the environment in order to perform realistic risk evaluations. Risk evaluation itself, particularly the summation of the effects of numerous distinct mutagens, may be assisted by adopting a common measure of mutagenicity such as the REC (rem-equivalent-chemical). Finally, the Committee 17 report laid out highly specific recommendations concerning maximum permissible exposures to environmental mutagens. Federal regulatory agencies and their enabling legislation are in fact evolving toward the effective control of this highly complicated problem.     

Structure and Action of Nemertine Toxins

Bacq (1936, 1937) discovered two substances by pharmacologicalexperiments using whole body extracts of various nemertine species."Amphiporine," found only in hoplonemertines, stimulated nicotinicacetylcholine receptor-mediated events. "Nemertine" evoked spontaneousaction potentials in isolated crab nerves. Both substances causedconvulsions when injected into crabs. Anabaseine, a pyridinealkaloid isolated from the hoplonemertine Paranemertes peregrina,has chemical and pharmacological properties equivalent to "amphiporine."Hoplonemertines produce a wide variety of pyridine toxins dependingon the species. The heteronemertine Cerebratulus lacteus contains cytolytic(10,000 dalton) and neurotoxic (6,000 dalton) proteins. Theneurotoxic polypeptides most closely resemble "nemertine": theycause repetitive spiking in isolated crustacean axons. Severalcytolytic and neurotoxic "isotoxins" occur within Cerebratulus. Both the hoplonemertine and heteronemertine toxins are localizedin the integumentary tissues of the body wall and proboscis.So far, the pyridine alkaloid toxins are only found in the Enoplanspecies, where they probably function as both offensive anddefensive toxins. Protein toxins have only been found in Anoplanspecies; they probably serve as a chemical defense against somepredators.     

Ecological engineering: A field whose time has come

Ecological engineering is defined as “the design of sustainable ecosystems that integrate human society with its natural environment for the benefit of both.” It involves the restoration of ecosystems that have been substantially disturbed by human activities such as environmental pollution or land disturbance; and the development of new sustainable ecosystems that have both human and ecological value. While there was some early discussion of ecological engineering in the 1960s, its development was spawned later by several factors, including loss of confidence in the view that all pollution problems can be solved through technological means and the realization that with technological means, pollutants are just being moved from one form to another. Conventional approaches require massive amounts of resources to solve these problems, and that in turn perpetuates carbon and nitrogen cycle problems, for example. The development of ecological engineering was given strong impetus in the last decade with a textbook, the journal Ecological Engineering and two professional ecological engineering societies. Five principles about ecological engineering are: (1) It is based on the self-designing capacity of ecosystems; (2) It can be the acid test of ecological theories; (3) It relies on system approaches; (4) It conserves non-renewable energy sources; and (5) It supports biological conservation. Ecology as a science is not routinely integrated into engineering curricula, even in environmental engineering programs, while shortcoming, ecologists, environmental scientists, and managers miss important training in their profession—problem solving. These two problems could be solved in the integrated field of ecological engineering.     

Statistical basis for positive identification in forensic anthropology

Forensic scientists are often expected to present the likelihood of DNA identifications in US courts based on comparative population data, yet forensic anthropologists tend not to quantify the strength of an osteological identification. Because forensic anthropologists are trained first and foremost as physical anthropologists, they emphasize estimation problems at the expense of evidentiary problems, but this approach must be reexamined. In this paper, the statistical bases for presenting osteological and dental evidence are outlined, using a forensic case as a motivating example. A brief overview of Bayesian statistics is provided, and methods to calculate likelihood ratios for five aspects of the biological profile are demonstrated. This paper emphasizes the definition of appropriate reference samples and of the "population at large," and points out the conceptual differences between them. Several databases are introduced for both reference information and to characterize the "population at large," and new data are compiled to calculate the frequency of specific characters, such as age or fractures, within the "population at large." Despite small individual likelihood ratios for age, sex, and stature in the case example, the power of this approach is that, assuming each likelihood ratio is independent, the product rule can be applied. In this particular example, it is over three million times more likely to obtain the observed osteological and dental data if the identification is correct than if the identification is incorrect. This likelihood ratio is a convincing statistic that can support the forensic anthropologist's opinion on personal identity in court.     

Beyond Paradise—Meeting the Challenges in Tropical Biology in the 21st Century

Tropical ecosystems support a diversity of species and ecological processes that are unparalleled anywhere else on Earth. Despite their tremendous social and scientific importance, tropical ecosystems are rapidly disappearing. To usher tropical ecosystems and the human communities dependent upon them through the environmental transformations of the 21st century, tropical biologists must provide critical knowledge in three areas: 1) the structure and function of tropical ecosystems; 2) the nature and magnitude of anthropogenic effects on tropical ecosystems; and 3) the socio‐economic drivers of these anthropogenic effects. To develop effective strategies for conservation, restoration, and sustainable management of tropical ecosystems, scientific perspectives must be integrated with social necessities. A new set of principles built on a framework for pursuing relevant tropical biological research will facilitate interdisciplinary approaches, integrate biological knowledge with the social sciences, and link science with policy. We propose four broad recommendations for immediate action in tropical biology and conservation that are fundamental to all biological and social disciplines in the tropics: 1) assemble and disseminate information on life's diversity in the tropics; 2) enhance tropical field stations and build a worldwide network to link them with tropical field biologists at their field sites; 3) bring the field of tropical biology to the tropics by strengthening institutions in tropical countries through novel partnerships between tropical and temperate zone institutions and scientists; and 4) create concrete mechanisms to increase interactions between tropical biologists, social scientists, and policy makers.     

Towards an Integrated Ecosystem-Based Bioaccumulation and Metal Speciation Model

Heavy metal bioaccumulation models are important for interpreting water quality data, predicting bioaccumulation in organisms, and investigating the provenance of contaminants. To date they have been predominantly used as single-issue models, under steady-state conditions and in isolation of the biogeochemical processes that control metal bioaccumulation. Models that incorporate these processes would allow a more holistic approach to bioaccumulation modeling and contaminant assessment; however, this has been rarely undertaken, probably because it requires the integration of inter-disciplinary areas. In this study, we have developed such a model that integrates three key multi-disciplinary areas (biological, metal speciation, and bioaccumulation processes) and responds to variations in temporal external and internal forcing. Furthermore, spatial context is provided by developing the model within a simple hydrodynamic box-modeling framework. The calibrated model was able to predict with reasonable accuracy the temporal and spatial trends of soft-tissue copper bioaccumulation in a coastal oyster. This exploratory model was also used to highlight the importance of phytoplankton as an important vector of copper uptake dynamics by an oyster, therefore reinforcing the importance of the integrated approach. Finally, our model provides a framework for greater application beyond this specific example such as in the areas of waterway restoration, which has been shown to be an important area of ecological and environmental research.     

"Are we there yet?": Deciding when one has demonstrated specific genetic causation in complex diseases and quantitative traits

Although mathematical relationships can be proven by deductive logic, biological relationships can only be inferred from empirical observations. This is a distinct disadvantage for those of us who strive to identify the genes involved in complex diseases and quantitative traits. If causation cannot be proven, however, what does constitute sufficient evidence for causation? The philosopher Karl Popper said, "Our belief in a hypothesis can have no stronger basis than our repeated unsuccessful critical attempts to refute it." We believe that to establish causation, as scientists, we must make a serious attempt to refute our own hypotheses and to eliminate all known sources of bias before association becomes causation. In addition, we suggest that investigators must provide sufficient data and evidence of their unsuccessful efforts to find any confounding biases. In this editorial, we discuss what "causation" means in the context of complex diseases and quantitative traits, and we suggest guidelines for steps that may be taken to address possible confounders of association before polymorphisms may be called "causative."     

Modern synthetic efforts toward biologically active terpenes

Terpenes represent one of the largest and most diverse classes of secondary metabolites, with over 55,000 members isolated to date. The terpene cyclase enzymes used in nature convert simple, linear hydrocarbon phosphates into an exotic array of chiral, carbocyclic skeletons. Further oxidation and rearrangement results in an almost endless number of conceivable structures. The enormous structural diversity presented by this class of natural products ensures a broad range of biological properties-ranging from anti-cancer and anti-malarial activities to tumor promotion and ion-channel binding. The marked structural differences of terpenes also largely thwart the development of any truly general strategies for their synthetic construction. This review focuses on synthetic strategies directed toward some of the most complex, biologically relevant terpenes prepared by total synthesis within the past decade. Of crucial importance are both the obstacles that modern synthetic chemists must confront when trying to construct such natural products and the key chemical transformations and strategies that have been developed to meet these challenges.     

The destruxins: synthesis, biosynthesis, biotransformation, and biological activity

Destruxins, secondary metabolites first reported in 1961, are cyclic hexadepsipeptides composed of an alpha-hydroxy acid and five amino acid residues. The name "destruxin" is derived from "destructor" from the species Oospora destructor, the entomopathogenic fungus from which these metabolites were first isolated. Individual destruxins differ on the hydroxy acid, N-methylation, and R group of the amino acid residues; where established, the configurations of the amino acid residues are S, and those of the hydroxy acids are R. Destruxins exhibit a wide variety of biological activities, but are best known for their insecticidal and phytotoxic activities. The great interest in destruxins derives from their potential role as virulence factors in fungi, whether such microorganisms are useful insect biocontrol agents or detrimental, causing great plant disease epidemics. Reports on isolation, chemical structure determination, total synthesis, transformation by diverse organisms, and biological activity of destruxins and related metabolites are reviewed for the first time.     

海绵硅蛋白研究进展

海绵是生物进化过程中最古老的多细胞动物,其中大部分能够利用二氧化硅在常温水环境下合成形状、大小和结构极为丰富的硅质骨骼。随着近年来人们发现其骨骼的基本组成单位骨针具有优异的光导性能和机械性能,海绵生物硅化过程及仿生纳米和微米硅质生物材料合成的研究成为生物技术和材料科学的热点。在海绵生物硅化过程中,一类被称为硅蛋白(Silicatein)的蛋白质表现出了特殊的催化活性,也因此得到了生物学家、化学家和材料学家的关注。以下将对硅蛋白的国际研究现状进行了评述,以期促进国内相关领域的研究。     

Terminology for contractions of muscles during shortening, while isometric, and during lengthening.

Communication among scientists must be clear and concise to avoid ambiguity and misinterpretations. The selection of words must be based on accepted definitions. The fields of biomechanics, muscle physiology, and exercise science have had a particularly difficult time with terminology, arising from the complexity of muscle contractions and by the use of inappropriate terminology by scientists. The dictionary definition of the verb "contract," specifically for the case of muscle, is "to undergo an increase in tension, or force, and become shorter." Under all circumstances, an activated muscle generates force, but an activated muscle generating force does not invariably shorten! During the 1920s and 1930s, investigators recognized that the interaction between the force generated by the muscle and the load on the muscle results in either shortening, no length change (isometric), or lengthening of the muscle. The recognition that muscles perform three different types of "contractions" required that contraction be redefined as "to undergo activation and generate force." Modifiers of contraction are then needed to clarify the lack of movement or the directionality of movement. Despite the contradiction, for 75 years the lack of movement has been termed an "isometric contraction." The directionality of the movement is then best described by the adjectives "shortening" and "lengthening." The definitions of "concentric" as "having the same center" and of "eccentric" as "not having the same center" are consistent with hypertrophy, or remodeling of the heart muscle, but are inappropriate to describe the contractions of skeletal muscles.     

The Role of Microbes in Agriculture: Sergei Vinogradskii’s Discovery and Investigation of Chemosynthesis, 1880–1910

In 1890, Sergei Nikolaevich Vinogradskii (Winogradsky) proposed a novel life process called chemosynthesis. His discovery that some microbes could live solely on inorganic matter emerged during his physiological research in 1880s in Strassburg and Zurich on sulfur, iron, and nitrogen bacteria. In his nitrification research, Vinogradskii first embraced the idea that microbiology could have great bearing on agricultural problems. His critique of agricultural chemists and Kochian-style bacteriologists brought this message to the broader agricultural community, resulting in an heightened interest in biological, rather than chemical methods to investigate soil processes. From 1891 to 1910, he directed the microbiological laboratory at the Imperial Institute of Experimental Medicine in St. Petersburg, Russia, where he expanded his chemosynthesis research to a broad investigation of the manifold significance of autotrophic organisms in soil processes. This work and that of his students attracted the serious attention of agricultural chemists and soil scientists in Russia and abroad, changing essentially the way they understood and investigated the role of microbes in the soil. His student, Vasilii Omelianskii, effectively integrated Vinogradskii’s approach into Russian and Soviet, and international agricultural microbiology. Vinogradskii’s activities in the late 19th century reflect the changes occurring more broadly in science. At that time, microbiologists such as Louis Pasteur, Eugenius Warming, and Martianus Beijerinck were contributing new laboratory methods and theoretical perspectives to incipient disciplines closely related to agriculture: ecology, soil science, and soil microbiology.     

Evolution of reproductive-immune interactions

The comparative approach in biological sciences has providedvaluable insights into the role of different organ systems inadaptation and evolution, and seeks to establish unifying themes.This approach also plays a key role in identifying model speciesand systems for the study of specific questions and problems.Further, by applying the concept of homology, information aboutnonmammalian species may be used either to directly understandmammalian/human regulatory processes, or to formulate hypothesesfor direct testing. Individual physiological systems functionin a milieu provided by the integrated activities of all ofthe systems to adapt, adjust and sustain the organism in itsenvironment. The overlapping interfaces between the differentphysiological systems provide fertile ground for new insightsand to enhance our knowledge. These interdisciplinary areasare of great importance if we are to understand the full complexityof organismal function. Of particular interest are the interactionsbetween the reproductive system and the immune system. The reproductivesystem is unique in that its primary role is to assure the continuityof the species, while the immune system provides internal protectionand thus facilitates continued health and survival. The modusoperandi of these 2 morphologically diffuse systems involveswidely distributed chemical signals in response to environmentalinput, and both systems must interact for the normal functioningof each. While the major focus of reproductive–immuneresearch has historically been with mammals, and has providedsubstantial insight into the interactions between these physiologicalsystems, comparative studies offer unique perspectives. Further,dysregulation of normal physiological interactions between thereproductive and immune systems can lead to disorders and diseaseseffecting one system or the other. Thus, comparative studiesof these interactions may shed some light upon the evolutionarymechanisms involved in such cases.     

Path-based systems to guide scientists in the maze of biological data sources

Fueled by novel technologies capable of producing massive amounts of data for a single experiment, scientists are faced with an explosion of information which must be rapidly analyzed and combined with other data to form hypotheses and create knowledge. Today, numerous biological questions can be answered without entering a wet lab. Scientific protocols designed to answer these questions can be run entirely on a computer. Biological resources are often complementary, focused on different objects and reflecting various experts' points of view. Exploiting the richness and diversity of these resources is crucial for scientists. However, with the increase of resources, scientists have to face the problem of selecting sources and tools when interpreting their data. In this paper, we analyze the way in which biologists express and implement scientific protocols, and we identify the requirements for a system which can guide scientists in constructing protocols to answer new biological questions. We present two such systems, BioNavigation and BioGuide dedicated to help scientists select resources by following suitable paths within the growing network of interconnected biological resources.     

Plant extracts as modulators of genotoxic effects

Higher plants used extensively in traditional medicines are increasingly being screened for their role in modulating the activity of environmental genotoxicants. The property of preventing carcinogenesis has been reported in many plant extracts. The observation of a close association between carcinogenesis and mutagenesis has extended the survey to include plant extracts and plant products able to modify the process of mutagenesis, which involves alteration in the genetic material. Natural plant products may, apart from inducing mutations, modify the action of other known mutagens on the living organisms by 1) activating the existing mutagens within the cell, 2) inhibiting the production of mutagens in the cell, 3) synergising the activity of existing mutagens, or 4) activating the promutagens within the cell into mutagens. This review deals with data obtained in the course of research on the modulatory effects of plant extracts on mutagenesis and clastogenesis, two genotoxic phenomena associated with carcinogenesis. In screening for antimutagenic effects, extracts of different plant parts have been used, ranging from leafy vegetables, fruits, and underground storage organs to whole plants. The extracts were prepared mainly in water or organic solvents. Several of these assays have indicated the involvement of certain factors that are intrinsic components of the extracts, ranging from specific compounds like ascorbic acid to vegetable fibres which could act as nonspecific redox agents, free radical scavengers, or ligands for binding metals or toxic principles. The possible ways in which inhibitors of mutagenesis can act include the inhibition of interaction between genes and biochemically reactive mutagens and the inhibition of metabolic activation of indirectly acting mutagens. The effects of toxicants can be observed at the level of chromosomes (clastogenesis) through alterations in chromosome structure (chromosomal aberrations) and number (aneuploidy, polyploidy). A wide range of short-term and long-term screening procedures is available. The most common ones use higher plants or rodents in vivo as test systems for monitoring chromosomal aberrations. Experiments with a number of crude vegetable and fruit extracts have demonstrated their anticlastogenic activities against known cytotoxic agents. The individual components of the extracts—e.g., sulfhydryl and flavonoid compounds, gallic acid, ellagic acid, mucic acid, citric acid, reducing sugars, tannin—are observed to have an additive interaction with the major constituents chlorophyll and ascorbic acid, when modulating the effects of the clastogens. Under certain conditions, plant products may induce mutagenic effects, due to the presence of multiple biological properties. Some inhibitors can stimulate simultaneously both enhancing and detoxifying mechanisms, e.g., inducers of coordinated enzyme activities. Many oxidants can, depending on the redox potential, either accept or donate electrons, rendering them protective or harmful. Plants also play an active role in the accumulation, metabolism, and environmental distribution of xenobiotics. The property of plants to activate promutagens that may enter the food chain is of great significance in view of the large number and types of chemicals to which the plants are exposed. A promutagen is a chemical that is not mutagenic itself but that can be biologically transformed by a plant system into a mutagen. Several methods for studying promutagens from plants were developed both in vivo and in vitro, including plant cell-free systems. Both mutagens and antimutagens can be extracted from the same plant extract depending on the nature of solvents used for extraction. Interaction between inhibitors may lead to synergistic effects. Such combined action may take place through the different inhibitors acting at different levels or being localised at different cellular areas. The greater protection afforded by crude plant extract as compared with an equivalent amount of the purified or synthetic ingredients, as observed withPhyllanthus emblica L. andBeta vulgaris L. var.benghalensis Hort., may be related to this phenomenon. Specific biological action of a drug is due to its specific binding to a functional molecular receptor. In complex plant extracts, the variable observed effects can be attributed to the many chemically reactive species that are formed during the processing and ingestion of the extract, which could act as non-specific redox agents, scavengers of free radicals, and ligands for binding to toxicants. The final effects are obviously the outcome of interactions between the components and their individual and collective interaction with the toxicant. The specificity and efficacy of such responses will be influenced also by the physiological factors influencing the plants and the process of administration of the extract. In utilizing pharmacologically active herbs, both beneficial and potential adverse effects must be taken into account. The actual dose and form of the plant also need to be worked out.