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Several plant-derived cancer drugs were discovered by examining the use of plants in traditional medicine,1,2 for example etoposide and teniposide, which are derived from the lignan podophyllotoxin, isolated from Podophyllum spp. (Berberidaceae). Podophyllum was used by several American and Asian cultures for the treatment of skin cancers and warts.3,4 Here we report results from our chemical analysis of two neotropical tree species of the genus Guaiacum, which have a long history of use by indigenous societies of Central and South America to treat inflammatory diseases and cancer.5,6 In addition, Guaiacum extracts and “gum” have been employed extensively as antioxidant food additives.7 Correspondingly, the chemistry of Guaiacum species has been subject to numerous studies.8,9

Except for Dubinin's classic works in the 1950s, there is very little information on the natural history or population dynamics of feather mites (Astigmata: Acariformes, Pterolichoidea). We studied variation in numbers of the different life stages of the feather mite Proctophyllodes pinnatus (Nitzsch) (Analgoidea: Proctophyllodidae) on captive House Finches Carpodacus mexicanus (Muller) (Passeriformes: Fringillidae) from December 2003 to November 2004. Simultaneously, we also studied how preen gland secretion varied in those birds. We monitored 20 House Finches (10 individuals of each sex) for the presence of mites on their wing feathers. There was seasonal variation in the abundance and prevalence of mites on different individual birds. Most birds did not show any mites from December to April. Mite numbers started to increase in July and peaked in August–September. In September, we observed more mites of early stages than in any other months. We also observed higher proportions of adults in Augu...

The chemical composition of preen gland secretions of antbirds (Thamnophilidae and Formicaridae) and phylogenetically closely related Dendrocolaptidae, Tyrannidae and Pipridae were investigated to understand the role of environment in secretion components. The secretions of Thamnophilidae consisted of long chain acids, alcohols, esters, unsaturated hydrocarbons, and isoprenoids. Formicaridae secretions contained exclusively squalene and its derivatives. In Pipridae, secretions were made up of complex long chain esters. In Dendrocolaptidae, the secretions consisted of long chain esters of both saturated and monounsaturated acids combined with mono-alcohols and those of Tyrannidae consisted of long chain esters of saturated, mono- and tri-unsaturated acids with mono- and di-ols that were less complex. Higher molecular weight saturated and unsaturated components in tropical species suggest that the volatility of the secretion components is correlated to environmental temperatures experienced by the birds. Squalene is a precursor in steroid biosynthesis, but higher amounts in Formicaridae secretions suggest that it may have some additional functions.

Fruits of the native South American tree Melicoccus bijugatus Jacq. (Sapindaceae) are consumed for both dietary and medicinal purposes, but limited information is available about the phytochemistry and health value of M. bijugatus fruits. Fruit tissues of the Florida Montgomery cultivar were assessed for sugars, using gas chromatography, and for total phenolics, using UV spectroscopy. Reverse phase high performance liquid chromatography (HPLC) fingerprints of crude methanolic pulp, embryo and seed coat extracts were obtained at 280 nm. Phenolics were characterised by both HPLC UV/vis analysis and HPLC electrospray ionization tandem mass spectrometry. Major sugars detected in the pulp and embryo extracts were sucrose, followed by glucose and fructose. The glucose:fructose ratio was 1:1 in the pulp and 0.1:1 in the embryo. Total phenolic concentrations of the fruit tissues were in the order: seed coat > embryo > pulp. Phenolic acids were identified mostly in pulp tissues. Phenolic acids, flavonoids, procyanidins and catechins were identified in embryo tissues, and higher molecular weight procyanidins were identified in seed coat tissues. This study provides new information about the phytochemistry and the potential health value of the Montgomery cultivar M. bijugatus fruit tissues.

3 Abstract: A comparative study was made on the relative sensitivity of normal cells vis-a-vis transformed cells to the induction of apoptosis by the selected natural products. Oncoproteins predispose cells for apoptosis. Flourensia cernua, Ambrosia chamissonis and camptothecin, was used as stimuli to induce apoptosis in transformed cells. V-Cbl plasmid -whole plasmid carring the v-Cbl gene-( pGEX-KG-v-Cbl 8,000 kb) and empty vector ( pGEX-KG 5,000kb) was used for transfection of COS and NIH 3T3 cells. We hypothesized that the Cbl proteins could predispose the transformed cells to apoptosis, by making cells vulnerable to outside insult, could lead to their apoptotic death. Even with higher doses, such as 30 and 40 µL, of Flourensia cernua, apoptotic influence was not statistically significant -0.035% of all cells. Twenty microliter of Ambrosia chamissonis also produced a statistically insignificant number -0.040% of all cells. The presence of intact nuclei stained pink by Propidium Iodide was generally observed, indicating necrosis. After longer duration (72 h), a higher number of necrotic cells was always observed. Murine fibroblast NIH 3T3 cells were more often found to be necrotic than COS fibroblasts. Delivering DNA by transfection resulted in toxicity, leading to the constant presence of necrosis. Key wards: Apoptosis, fibroblast, natural products, necrosis, plasmid

In order to compare ant and non-ant defended species of Melastomataceae, production of hydrogen cyanide gas was tested in the field for 51 species of 10 genera of the tribe Miconieae. Using both the picric acid and the Feigl–Anger tests all populations surveyed tested negative for the presence of cyanogenic glycosides. These results confirm that cyanogenesis is rare in the family, although not completely absent. Cyanogenic glycosides are not responsible for the protection against herbivory in non-ant defended species, but this does not rule out that there are quantitative of qualitative differences in other secondary metabolites.

Resveratrol, a constituent found in grapes and various other plants, has been shown to have chemo-preventive activity against cancer, and specifically demonstrated to induce apoptosis by p53-dependent pathways in murine cells. The goal of this research was to identify the role of p53-dependent or p53-independent pathways in the induction of apoptosis in human breast cancer cells by this natural product.A number of human breast cancer cell lines, as well as a control of a wild-type line (astrocytoma N 1321N1), were investigated for induction of apoptosis by resveratrol using both microscopic evaluation and DNA fragmentation assays. Concurrently, we established the p53 gene status (wild-type or mutant) of each cell line by Western blot using p53-specific antibody.Apoptosis induced by resveratrol was found to occur only in breast cancer cells expressing wild-type p53 but not in mutant p53-expressing cells.We therefore conclude that the natural product, resveratrol, induces apoptosis in breast cancer cells via p53-dependent pathways.

Piperovatine, a sialogogic, piscicidal, and buccal local anesthesia producing isobutyl amide from the amazonian piscicidal and toothache-relieving plant, Piper piscatorum Trelease et Yuncker (Piperaceae), was evaluated for its ability to induce changes in neuronal intracellular calcium concentration. Ratiometric calcium imaging of Periplaneta americana neuronal cell cultures upon piperovatine application revealed that this compound induced dramatic increases in intracellular calcium concentration. Calcium flux was not affected by co-application of the muscarinic acetylcholine receptor antagonist, atropine, indicating that the parasympathomimetic system was not involved in piperovatine's sialogogic actions. Calcium flux was, however, totally eliminated by co-application of the voltage-gated sodium channel blocker, tetrodotoxin (TTX). This, in conjunction with the repetitive calcium spikes observed in the assay and previous radioligand binding studies on the chemical class, strongly suggest that activation of voltage-gated sodium channels characterizes piperovatine's mode of action

▪ Abstract Traditional herbal remedies have increased in popularity in Europe and the United States in recent years but have always been important to people living in rural Mexico and to their Mexican American/Chicano descendants in the United States. Mexican American patients will often be ingesting herbal teas at the same time that they are being treated for their ailments with antibiotics or antiinflammatory agents. The plant family Asteraceae (Compositae) has contributed the largest number of plants to this pharmacopoeia; the reasons for the importance of this family include its large number of species in Mexico and its wide array of natural products that are useful in the treatment of the maladies that have afflicted the inhabitants of rural Mexico. These natural products include sesquiterpene lactones, polyacetylenes, alkaloids, monoterpenes, and various phenolics such as flavonoids. In this review, we emphasize the sesquiterpene lactones, a large group of compounds with antiinflammatory properties and the ability to relax smooth muscles and thereby relieve gastrointestinal distress. These compounds also readily form adducts with glutathione or free thiols and can thereby affect the metabolism, activity, and toxicology of a wide array of pharmacological agents.

Hydroxylated anthraquinones have been found to accumulate in different developmental stages of the chrysomelid beetle Trirhabda geminata. Eggs, larvae and adults were analyzed by HPLC and GC-MS. Each developmental stage analyzed contained 1,8-dihydroxy-3-methyl-anthraquinone (chrysophanol) and 1,8-dihydroxyanthraquinone (chrysazin). No anthraquinones were detected in the faeces of T. geminata. The level of stored anthraqui­ nones did not change during starvation. In the host plant of this specialist herbivore, the brittlebush Encelia farinosa (Asteraceae), anthraquinones were not detected. Possible biolog­ical functions of anthraquinones stored in T. geminata are discussed.

A gel permeation chromatographic (GPC) method was developed for measuring the content and M r s of cis -polyisoprene in tissue cultures of guayule ( Parthenium argentatum ). Rubber production and growth rates were investigated in several morphogenetically distinct cultures, including normal and crown gall callus, and root and shoot cultures. These results were compared with rubber production in leaves and stems of whole plants. Tissue cultures yielded 1 to 10% of the rubber found in mature guayule stem tissue. The M r distributions of rubber from cultures were bimodal in contrast with that of rubber from whole plant stems which is unimodal. In the intact plant only the rubber from leaf tissue is bimodal with most of it contained in a M r fraction with a peak of 22 300. In contrast, the rubber peak in stems of young guayule plants was 500 000. Rubber from shoot and root cultures had average M r s of 150000 and 201 000 respectively, and normal and tumour callus cultures had M r s of 415 000 and 291 000. The ability of tissue cultures to make comparatively high M r rubber relative to whole plants supports the use of guayule tissue cultures for studies of rubber biosynthesis.

Several environmental and chemical factors affected rubber accumulation in guayule (Parthenium argentatum) tissue cultures. Light increased rubber yields in callus and shoot cultures by 50 and 450% respectively. The Mr of rubber in light-grown callus increased by 60%. Daily periods of incubating callus at 4° increased rubber yield by 70% after five weeks. Increasing sucrose levels up to 7% in the medium stimulated rubber synthesis, but higher levels were inhibitory. Osmotic stress significantly inhibited both rubber production and growth. Rubber production in callus was highest when the content of NO3− in culture medium was 30 mol% of total N when compared to NH4+. Two previously reported stimulators of rubber production in whole plants, acetate and DCPTA, also enhanced the levels of rubber in callus cultures.

Several acetogenins, characteristic of the Annonaceae, have been found to exhibit pesticidal and feeding-deterrent activities against a variety of pests and are undergoing commercial development as pesticides. The sensitizing potential of one of these plants, pawpaw, Asimina triloba Dunal, was examined in the current study. The potential of Fraction F020 (a pesticidal crude extract of pawpaw stem bark) to sensitize and elicit an allergic contact dermatitis response was determined by using a modified guinea pig maximization test (GPMT). Fraction F020 is a weak sensitizer and the active compound, asimicin, a trihydroxy-bistetrahydrofuran fatty acid gamma-lactone, is a weak irritant.

Extraction of the roots of the Amazonian medicinal plant, Piper piscatorum Trelease and Yuncker, with MeOH and subsequent bioassay guided fractionation using the guppy, Girardina guppii yielded the active amide, N-isobutyl-6-(p-methoxyphenyl) 2E, 4E-hexadieneamide (piperovatine) and a second inactive amide, N-isobutyl-(E)-7-(3,4-methylenedioxyphenyl)hept-2-enamide (pipercallosidine). The former displayed an LC50 of 115 ng/ml in toxicity tests and proved to be the constituent responsible for the dual ethnobotanical uses of this plant: that of fish stupefacient (barbasco) and oral local anesthetic.

Leaf beetles of the speciesTrirhabda geminata are specialized herbivores that are able to feed on the chemically well-protected foliage of the desert sunflowerEncelia farinosa, which contains the insecticidal chromene derivative encecalin. Chemical analysis of the beetles and their fecal excretions indicated that encecalin is present only in the alimentary canal and is not absorbed across the gut membrane, as previously shown for other herbivorous insects (e.g., the Egyptian armyworm,Spodoptera littoralis) that are susceptible to this chromene derivative. Further differences betweenT. geminata and nonadapted insects were observed with regard to the metabolism of encecalin. Whereas the encecalin-resistent leaf beetles metabolize encecalin mainly to encecalol by reduction of the acetyl group, susceptible insects, such as larvae ofS. littoralis, metabolize encecalin mainly by exoxidation of the 3,4 double bond, which creates a powerful alkylating agent and is responsible for the toxicity of encecalin. Reductive rather than oxidative metabolism of encecalin therefore seems important for the resistance ofT. geminata against the chemical defense of their host plantE. farinosa.

Aspects of recent research on the biological activities of sesquiterpene lactones (SQLs) are presented. Several SQLs have been identified as important constituents of plants consumed by animals for presumed medicinal value and is a focus of research in zoopharmacognosy. Recent in vivo antitumor studies with parthenin and eupatoriopicrin are discussed as well as the reports of the antiulcer activity of dehydroleucodin. Helenalin has recently been reported to have cardiotonic activity. Research on the neurotoxicity of repin, a compound reported to cause a Parkinson's-like disease in horses, is also highlighted.

The last years of the twentieth century offer both challenges and opportunities for phytochemists. The AIDS epidemic is still expanding and to date medical science has not been able to find effective treatments. Resistance to antibiotics, antimalarials, and other drugs occurs with increasing frequency. Crisis like these have created a new demand for phytochemical screening programs to detect antiviral plant products. Consequently the attention of phytochemists has turned to the tropical rain forests that contain most of the world’s species of plants and animals.

A unique group of bioactive, naturally occurring lipid aldehydes were isolated from the fruits of Viburnum opulus, (family Adoxaceae). The natural occurrences of these fatty acid derived aldehydes are reported here for the first time. Helicobacter pylori is a prevalent gastroduodenal pathogen, a causal agent of chronic gastritis and peptic ulcers and an important co-factor in gastric cancer development. We investigated the chemistry and bioactivity of these active constituents by evaluating their ability to inhibit the growth of H. pylori and to induce apoptosis in a gastric cancer cell line (CRL-5971) in vitro.

Age-specific concentrations of farinosin, a sesquiterpene lactone, and encecalin and euparin, both chromenes, were measured in two semi-desert populations of Encelia farinosa in California over a three month period. All three natural products differed significantly in concentration. The average concentration of encecalin is 10 times that of euparin and eight times that of farinosin. Farinosin concentrations did not differ between the two populations, but both euparin and encecalin were in higher amounts in the UC Riverside population than in the Home Gardens population. Seasonal changes in natural products differed at the 0.05 level for all populations and compounds except euparin in the UC Riverside population. Percent nitrogen content of dried leaves was similar in both populations, but differed between collection dates. Water content did not vary significantly with leaf age on one collection date. The significance of these results is discussed in the light of herbivore history.

Six plant-derived simple beta-carboline alkaloids and eight other plant derivatives were tested for activity against the protozoan parasite, Trypanosoma cruzi, the organism responsible for Chagas' disease. The plant alkaloids in this study were screened using an in vitro test against epimastigotes. Four beta-carboline indoles, a complex indole and five other alkaloids significantly reduced population growth of T. cruzi (Costa Rica strain) epimastigote forms at a concentration of 50 micrograms/ml or less.

La benzofuranne 6-methoxyeuparine et 2 chromenes l'encecaline et la 7 demethylencecaline provenant d'E. lacinata, E. palmeri et E. ventorum (Baja California, Mexique) se sont revelees phototoxiques vis-a-vis de plusieurs bacteries et levures en UV de grande longueur d'onde. L'encecaline a aussi montre une activite insecticide vis-a-vis des larves d'Oncopeltus fasciatus

β-Carboline alkaloids are found worldwide in many plant families. Harman, harmine, and other simple β-carboline alkaloids were tested for activity against a generalist phytophagous insect, the beet army worm [Spodoptera exigua (Hubner)]. Chronic dietary exposure tests (neonate to pupa) reveal potent antifeedant and possible toxic effects. Acute dietary exposure tests on fifth-instar larvae also demonstrate antifeedant activity.

Chemical studies of Psilostrophe cooperi afforded in addition to psilotropin, four unreported helenanolides, two methylated flavonoids and a new pseudoguaianolide, cooperin, with an unusual enol-moiety. The structure of cooperin was established by spectroscopic methods and confirmed by X-ray analysis. In addition, all the sesquiterpene lactones were tested for mutagenic activity.

This review discusses the biochemical action and ecological significance of phototoxic phytochemicals. Mechanistic details of photosensitization as well as cellular and molecular targets of plant-derived phototoxins in model biological systems (microbial and in vitro) and in herbivorous insects are described. Findings from these studies suggest the potential importance of phototoxic plant metabolites in plant-insect interactions. Aspects of phototoxin distribution and significance in diverse ecosystems are considered, and areas for future research are suggested.

BOT. GAZ. 141(4):435-439. 1980. © 1980 by The University of Chicago. 0006-8071 / 80/ 4104-0019$02.00 COMPARATIVE PHYTOCHEMISTRY OF PARTHENIUM HYSTEROPHORUS L. (COMPOSITAE) TISSUE CULTURES 1 KAREN WICKHAM,2 ELOY RODRIGUEZ, 3 AND JOSEPH ARDITTI Department of Developmental and Cell Biology, University of California, Irvine, California 92717 Roots, stems, petioles, and leaf blades of mature plants of Parthenimn hysterophoms and callus cultures derived from explants of these organs from aseptically grown seedlings were screened for the presence of sesquiterpene lactones. Parthenin was not detected in roots but was present in callus cultures from all sources. Coronopilin was detected only in petioles and leaf blades and callus cultures derived from these organs. These findings suggest that synthesis of parthenin and coronopilin is not limited to the glandular trichomes. Introduction Parthenium hysterophorus L. (Compositae), a plant indigenous to the Americas, has spread to Australia and India, becoming an aggressive weed. It contains the sesquiterpene lactone, parthenin (fig. 1), a constituent which causes allergic contact dermatitis in humans and is toxic to livestock (TOWERS et al. 1977). Because of the wide spectrum of biological activity exhibited by parthenin and related sesqui- terpene lactones, we developed a tissue culture method for studying its biosynthesis and localization. hot and still liquid medium. Test tubes (25 X 200 mm) containing 20 ml medium were used as culture vessels. Each tissue-medium combination was repli- cated 15 times. EXCISION OF EXPLANTS.- Cotyledons were ex- cised from newly germinated seedlings. Leaf blades, roots, stems, and petioles were removed from 30- 150-day-old plants. The leaf blades were cultured intact. After removal of petiole stubs, stems were sectioned into ca. 5-mm sections. Roots were cut into ca. 2.5-cm lengths. ExTRACTION.-Callus, roots, stems, leaf blades, or petioles were ground in chloroform and filtered (RODRIGUEZ 1976). If the filtrate contained water as well as CHC'3, the aqueous fraction was evaporated in vacuo to an oil. Components of the oil were moni- tored by TLC (silica gel G developed with ben- zene: acetone, 4: l, vol/vol). Individual components were visualized with iodine vapor and/ or concen- trated H2S01/ CcS04 (50:5, vol/wt) and 0.5 g vanil- lin d issolved in a solution of 9 ml EtOH and 0.5 m H 2S0 4 (PICMAN, RANIERI, and TOWERS 1980). Au- thentic samples of parthenin and coronopilin were cochromatographed with extracts (fig. 1). PREPARATORY CHROMATOGRAPHY FOR HPLC. - Material and methods SEED GERMINATION.- Seeds of Parthenium hy- sterophorus were sterilized with saturated calcium hypochlorite solution (WILSON 1915) containing 2- 5 drops of T ween 80 by shaking vigorously for 5 min and rinsing three times with sterile distilled water. Hoagland's solution (HOAGLAND and ARN ON 1938), solidified with 13 g agar/ liter and autoclaved, was used as the germination medium. Erlenmeyer flasks (125 ml), each containing SO ml medium and three or four seeds, were employed as culture vessels. The cultures were maintained under 22 ± 2 C, illumi- nated with 3 mW/ cm 2, and 18-h photo periods were provided by a combination of Gro Lux 40-W fluores- cent tubes and 25-W incandescent bulbs. TrssUE CULTURE.-Two media, Heller's (HEL- LER 1953) and MS (MURASHIGE and SKOOG 1962) were modified (table 1) by the addition of GAa, two auxins (NAA and 2,4-D), and three cytokinins (BAP, kinetin, and 6-DMAP) . The minerals, vita- mins, sugars, and agar were autoclaved. Hormones (stock solutions in 95% ethanol) were added to the PARTHENIN CORONOPILIN 1 Abbreviations used: BAP = benzylaminopurine; 2,4-D = dichlorophenoxyacetic acid; 6-DMAP = 6-dimethylamino- purine; GA3 = gibberellic acid; HPLC = high performance liquid chromatography; MS= Murashige-Skoog medium; NAA = naphthalene acetic acid; TLC= thin layer chroma- tography. 2 Undergraduate research project in phytochemistry and plant physiology. 3 Address for reprint requests. Manie.script received NQVember 1979; revised mamiscript rueived April 1980. FIG. 1.-Sesquiterpene lactones of Parthe11im11 hysterophoms and related species.

Summary Thiarubrines are dithiacyclohexadiene polyacetylenes displaying considerable antimicrobial activity. A culture that accumulates these compounds was obtained by selection of red-colored areas from crown gall tumor cultures of Chaenactis douglasii . The tumors were induced by A. tumefaciens strain A277. The main acetylenic products found were two thiarubrines, A and B, and their corresponding thiophenes. Average yields of thiarubrines and thiophenes were 2.5 and 0.24 mg/g dry weight respectively, which are similar to the values seen in intact plants. The products accumulate in intercellular spaces arranged around a core of vascular tissue, forming red nodules of varying size. The structures crudely resemble the tissue organization of the roots of this plant, the only organ where these compounds accumulate. Formation of rootlets, however, does not take place at any stage during the growth of the tumors. Evidence is presented suggesting that the accumulation of these polyacetylenes by the tumor line is not a direct result of cellular transformation but a secondary effect of the existing degree of tissue differentiation.

The distribution and quantitative significance of biosynthetically related di- and ter-thiophenes from 27 species representing seven genera of the Pectidinae (Heliantheae) was investigated by reverse-phase HPLC. Adenophyllum, Chrysactinia and Nicolletia , three previously unstudied genera, were found to contain thiophenes for the first time. Four derivatives, 5-(4-hydroxy-1-butenyl)-2,2′-bithiophene ( 1 ), 5-(4-acetoxy-1-butenyl)-2,2′-bithiophene ( 2 ), 5-(3-buten-1-ynyl)-2,2′-bithiophene ( 3 ) and 2,2′:5′,2″-terthiophene ( 4 ) were common constituents in most species of Adenophyllum, Chrysactinia, Dyssodia, Hymenatherum, Nicolletia and Porophyllum . One additional compound, 5-methyl-2,2′:5′,2″-terthiophene ( 5 ), was also present in extracts of Adenophyllum, Dyssodia and Hymenatherum , but was not detected in any other genus. Acetylenic thiophenes were not found in any of the 18 species of Pectis examined.

Over 20 taxa of the genus Partenium (Compositae) representing four sections or five ecological groupings from throughout the Americas, were examined for sesquiterpene lactones, flavonoids and alkaloids. The tropical thorn-forest, arborescent members (sect. Parthenichaeta) were found to contain three different sesquiterpene lactone types and derivatives of the flavonols; quercetin, kaempferol and quercetagetin. The desert shrubs were remarkable for their high production of methylated quercetagetin flavonols and alkaloids, but lacked any appreciable amounts of sesquiterpene lactones. The temperate, submontane perennials (sect. Bolophytum), contained lactones and flavonols in extremely low concentrations. The herbaceous annuals (sect. Argyrochaeta) contained pseudoguaianolides only and together with quercetin, and kaempferol O- glycosides . The herbaceous perennials contained twice as many lactones and flavonoids as the annuals. It is suggested that the ecogeographical distribution of secondary products in Parthenium is probably a result of adaptive responses to various physical and biotic factors (herbivore pressure) in the environment.

The genus Parthenium includes one species, guayule (P. argentatum Gray), that produces large amounts of good quality rubber. At present, guayule is the subject of research to determine if it can be developed as an alternative crop for the arid areas of the United States and other countries. Interspecific hybridization between guayule and other species of Parthenium can be accomplished without major difficulties, and there are several desirable agronomic traits that can be transferred from these species to guayule. These other species have not been reported to have large amounts of rubber. Rollins reported that some biotypes of Parthenium incanum H.B.K. contain small amounts of rubber. Taylor and Benedict reported that P. tomentosum D.C. var. stramonium (Greene) Rollins contained 0.02% rubber. Angulo-Sanchez examined 21 guayule plants from native stands near Saltillo and found Mw values varied between 6.10×104, 6.10×105, and 1.13×106; Mn values varies between 6.10×104 and 6.10×105 (Reference 7). These values are comparable to Hevea clones examined by Subramanian. In this study, the molecular weights of guayule and five species of Parthenium are reported, the F1 hybrids between guayule and one of these species, P. alpinum was also examined to determine the size of polymers that characterize this particular hybrid.

Sesquiterpene lactones are characteristic constituents of the Compositae but also occur sporadically in other angiosperm families and even in some liverworts. These bitter substances often contain as a major structural feature an α,β-unsaturated-γ-lactone, which in recent studies has been shown to be associated with anti-tumor, cytotoxic, anti-microbial and phytotoxic activity. They are known to poison livestock, to act as insect feeding deterrents and to cause allergic contact dermatitis in humans. This review highlights the present state of knowledge on the biological activities and mechanism of action of some sesquiterpene lactones.

Sixteen taxa of the genus Parthenium from North and South America and 20 sesquiterpene lactones derived from plants of the Compositae family were used for patch testing six volunteers who were known to be contact sensitive to plants and lactones of this family. The patterns of cross-sensitivity and structure-activity relationships of the allergenic lactones are evaluated and the clinical and ecological relevance is discussed.

Callus cultures were initiated in leaf and influorescence explants from mature guayule rubber plants ( Parthenium argentatum ). Initial cultures were morphologically heterogeneous and contained leaf and shoot primordia. These structures were substantially eliminated by serially subculturing only the least organized callus-like tissues. The selected calli from inflorescences have exhibited stable morphogenetic properties and growth rates for over one year. These cultures produced chlorophyll when grown under illumination and chemical analyses of both light- and dark-grown calli showed the presence of alkanes, sesquiterpenoids and cis -1,4-polyisoprene (rubber). Callus contained the same alkane species that were previously found in leaves of mature plants. Similarly, the predominant n -alkanes in both callus and plants had the carbon chain lengths C 29 and C 31 . The proportions of alkane size classes differed between tissue sources. A change in pattern from longer to shorter alkanes was found according to the order: mature leaves, light-grown callus and dark-grown callus. Two sesquiterpene phenolic esters (guayulin-A and -B), allergenic compounds found in guayule plants, were present in guayule callus at about 4% of levels found in whole plants. Light had a negligible influence on production of the guayulins but showed a larger effect on rubber synthesis; light-grown callus produced about ten times the amount of rubber produced by dark-grown callus. The appearance of these important secondary hydrocarbons in long-term guayule tissue cultures represents a useful system for further studies of the regulation of these chemicals.

The dermatitic constituents of the glandular hairs of plants in the family Hydrophyllaceae comprise a class of uncommon natural products called "phacelioids". The chemical structures consist of various elaborations of hydroquinone attached to a C10 to C20 prenyl chain. Certain of these compounds are equivalent to the urushiols of Toxicodendron (Rhus) in their capacity to sensitize humans. Although structurally related to the urushiols, the phacelioids do not appear to cross-react in humans either with urushiol, or between phacelioids with different prenyl chains.

Natural products isolated from various species of Parthenium were fed (in artificial diets) to the herbivorous insects Heliothis zea and Spodoptera exigua to assess the ability of the compounds to inhibit larval growth. Sesquiterpene esters and triterpenes from guayule ( P.argentatum ) were relatively non-inhibitory over a range of concentrations reflecting those in the plant. A quercetagetin-based methylated flavonoid from guayule was equitoxic to quercetin, whereas a kaempferol-based methylated flavonoid was stimulatory to both insect species. Sesquiterpene lactones from Parthenium were consistently inhibitory to H. zea ; those oxygenated at C-14 and/or C-15 (parthenolides) were more inhibitory than their unsubstituted ambrosanolide analogues. At a dietary concentration of 3.0 mM/kg fr. wt, tetraneurin-A (a parthenolide) reduced larval growth of H. zea by 88 % relative to controls in a chronic feeding bioassay.

Chromenes (benzopyrans) and benzofurans are characteristic natural products of certain tribes of the Asteraceae. This review highlights recent findings

Artifical diets incorporating powdered foliage or foliar extracts of Parthenium tomentosum DC. or P. schottii Greenman inhibited feeding, growth, and dietary use by 3rd-instar larvae of the beet armyworm, Spodoptera exigua Hubner, relative to larvae feeding on diets incorporating foliage or foliar extracts from guayule, P. argentatu Gray, or an F1 hybrid of guayule with P. tomentosum. Amixture of sesquiterpene lactones isolated from P. schottii added to an artifical diet inhibited feeding, but did not deter growth or dietary use by larvae. Foliage or foliar extracts of P. schottii added to diets also significantly inhibited growth and dietary use by 3rd-instar larvae of the bollworm Heliothis zea (Boddie), although there was no reduction in consumption rate. In contrast, powdered inflorescences of P. schottii or extracts thereof, both rich in sesquiterpene lactones, deterred neither feeding nor growth of H. zea when added to artificial diets. Confertin, the principal sesquiterpene lactone of P. schottii foliage and inflorescences, had no effect on feeding or growth of 3rd-instar larvae, even at a concentration which strongly inhibits growth of neonate H. zea larvae. Chemical factors in P. schottii and P. tomentosum foliage appear to inhibit larval growth of both S. exigua and H. zea, although a contribution to that inhibition by sesquiterpene lactones is uncertain.

Encelia farinosa Gray (Asteraceae: Heliantheae), a common shrub of the Sonoran desert, contains both sesquiterpene lactones and chromenes. Chloroform extracts of E. farinosa leaves were deterrent to larvae of Heliothis zea (Boddie) in choice tests, but farinosin, a eudesmanolide sesquiterpene lactone from E. farinosa , was not. Five sesquiterpene lactones from different Asteraceous genera were examined for their effect on the relative growth rate (RGR) of H. zea at 0.1% fresh weight in an artificial diet. Only dchydroleucodin, a guaianolide sesquiterpene lactone from Artemisia tridentata spp. vaseyana , reduced growth. Three closely related chromenes (precocene 1 and 2 and encecalin) were examined for their effects on survivorship (SR) and RGR of H. zea at five different concentrations. Precocene 1 and 2 exhibited the greatest activity on survivorship and growth rates, whereas encecalin was less active.

The principal phenolic constituents were isolated from the exudate of the glandular trichomes of TURRICULA PARRYI, a California shrub that causes severe contact dermatitis. The phenolic constituents consist of a complex mixture of methoxylated flavones and derivatives of both farnesylhydroquinone and 3-farnesyl- P-hydroxybenzoic acid in which the C-7 methyl of farnesyl is replaced by hydroxymethyl, formyl and carboxyl groups. Elicitors of allergic contact dermatitis were identified with guinea pigs sensitized to the crude exudate. The principal agents of dermatitis were the farnesyihydroquinone derivatives 3 and 6.

The components of the two major classes of natural products of the composite Encelia farinosa , sesquiterpene lactones and benzopyrans/benzofurans (chromenes), were resolved and quantified by high performance liquid chromatography. Geographic variation was examined over a range of mesic and xeric populations from California and Arizona (USA). The concentration of farinosin, a sesquiterpene lactone, varies significantly between individuals and seasonally within individuals. Ontogenetic comparisons revealed interpopulation variations within sesquiterpene lactones and chromenes. A geographic survey suggests the presence of two putative chemical races which vary in the amounts of sesquiterpene lactones and chromenes present. The adaptive significance of this quantitative variation is discussed.

The capacity of a reversed-phase high-performance liquid chromatographic system using Ultrasphere-ODS columns and a gradient of acetonitrile—water to separate sesquiterpene lactones has been studied. Retention times and capacity factors of 33 compounds of the pseudoguaianolide and xanthanolide skeletal types occurring in Parthenium (Asteraceae) are reported. Crude extracts of Parthenium schottii containing a mixture of sesquiterpene lactones have been analyzed and separated using the high-performance liquid chromatographic system.

A high performance liquid chromatographic method for analyzing phenolic acids on reverse phase C-18 is described. Twelve substituted benzoic and cinnamic acid derivatives as well as the parent acids were resolved in less than 25 min. Separation was achieved by using a step-wise gradient of three different solvent systems and by adding ammonium acetate for preventing intramolecular hydrogen bonding of the acids. The applicability of the described m ethod to crude plant extracts is demonstrated with Adenostoma fasciculatum, Adenostoma sparsifolium and Phyllospadix scouleri. The percent composition of the phenolic acids within the three extracts is given.

The principal dermatitic constituents of W. caracasana were isolated from the glandular hairs and identified as unusual prenylated quinones and prenylated phenols. Potentials to elicit irritant and allergic contact dermatitis reactions were evaluated with guinea pigs.

In a human maximization test of 5% falcarinol isolated from Hedera helix, 10 of 20 subjects were sensitized. No subjects gave irritant reactions to 5%, 10 became sensitive to 1%, and 7 to 0.05%, with 3 of these giving 3+ to 4+ bullous reactions.