J. Thor Arnason

Stimulation of interleukin-1 and -6 production in alveolar macrophages by the neotropical liana, Uncaria tomentosa (Una de Gato)

Two extracts of different collections of the traditional medicine uña de gato (Uncaria tomentosa) from Peru were characterized by High Pressure Liquid Chromatography as containing approximately 6 mg/g total oxindole content prior to studies with alveolar macrophages. The plant preparations greatly stimulated IL-1 and IL-6 production by rat macrophages in a dose dependent manner in the range of 0.025-0.1 mg/ml. They were also able to enhance IL-1 and -6 in lipopolysaccharide-stimulated macrophages. The results suggest a strong immunostimulant action of this plant.

Structure-activity studies of photoactivated antiviral and cytotoxic tricyclic thiophenes

The photoactivated antiviral and cytotoxic activities of the naturally occurring thiophene, α‐terthienyl (1), and 15 synthetic analogues were evaluated against murine cytomegalovirus and Sindbis virus, and murine mastocytoma cells. After irradiation with near UV light, α‐terthienyl and most of its analogues had significant toxicity, with minimum inhibitory concentrations in the range of 0.02–40 μM. In the absence of near UV irradiation, only one analogue had antiviral activity and five were cytotoxic. The most active analogues were those containing carboxylic acid, hydroxyl, or cyano substituents. Quantitative structure‐activity relationship analysis of thiophene phototoxicity suggested that the rate of singlet oxygen production is the primary determinant of antiviral and cytotoxic activities. For phototoxicity against murine cytomegalovirus, a significant role for hydrophobicity was also demonstrated. Tricyclic thiophenes show significant potential for photochemotherapy of viral infections and cancer. and further evaluation in animal models is recommended.

Echinacea purpurea. Aerial Parts Contain Multiple Antiviral Compounds

Abstract Stems, leaves, and flowers of Echinacea purpurea. (L.) Moench (Heliantheae: Asteraceae) were fractionated by various solvents and the fractions evaluated for antiviral activity in relation to chemical composition and distribution within the plant. All of the aqueous fractions contained potent activity against herpes simplex virus and influenza virus. However, although some of this activity could be attributed to polysaccharide and cichoric acid components, their individual contributions could not account for the total antiviral activity; other potent antivirals must be present. In addition, the ethanol- and ethyl acetate–soluble fractions from leaves and stem contained an uncharacterized but potent antiviral photosensitizer, which was absent from the flower extract. None of the fractions, however, contained anti-rhinovirus activity. Thus, part of the alleged benefits of Echinacea purpurea. extracts can be attributed to the presence of anti-influenza and anti-HSV compounds, and some of these activities are likely to be present in various commercial tinctures, teas, capsules, and tablets.

Alfalfa Leaf Saponins and Insect Resistance

Dried alfalfa (Medicago sativa) leaf tissue incorporated in artificial diet to give a final concentration of 0.5 or 1.6 mg/g fresh weight of saponins significantly inhibited growth and development of larvae of the European corn borer (Ostrinia nubilalis). Saponin fractions isolated from root or shoot tissues of alfalfa also inhibited growth when incorporated at equivalent concentrations but had little effect on development. Root saponins were somewhat more harmful than shoot saponins.

Characterization of Antiviral Activities in Echinacea. Root Preparations

Abstract The roots of three commonly used taxa of Echinacea.—E. purpurea., E. pallida. var. pallida., and E. pallida. var. angustifolia.—were extracted and fractionated by means of accelerated solvent extraction to reflect the most commonly used methods for commercial preparations. These fractions were analyzed by HPLC for their content of caffeic acid derivatives and alkamides and for antiviral activities against three viruses often implicated in colds and influenza. Aqueous extracts of E. purpurea. root contained a relatively potent activity against herpes simplex virus (HSV) and influenza virus (FV) but not against rhinovirus (RV). These fractions had low amounts of caffeic acids and alkamides. The ethyl acetate fraction contained significant but weak activity against both HSV and FV and contained significant levels of cichoric acid. In contrast, E. pallida. var. angustifolia. gave no water-soluble antiviral activity, but the ethanolic and ethyl acetate fractions contained significant activity against all three viruses, and this activity correlated with the presence of alkamides. E. pallida. var. pallida., however, gave no antiviral activity in any of the fractions, and this observation accorded well with the near absence of the marker compounds. Thus, we have detected a relatively potent water-soluble antiviral activity in E. purpurea. root, together with the weaker antiviral cichoric acid; an antiviral alkamide fraction in E. pallida. var. angustifolia.; but no antiviral activity in E. pallida. var. pallida.. Therefore, different types of Echinacea. root preparations, such as tinctures, tablets, and teas, based on different species and extraction methods, would be expected to offer quite different antiviral profiles.

How do insect herbivores cope with the extreme oxidative stress of phototoxic host plants

Plants of the Asteraceae and Hypericaceae possess secondary compounds that induce photooxidation in insect herbivores that consume them. One of the well-established modes of action of these substances is peroxidation of membrane lipids. Some herbivores counteract these defences by avoidance of light and tissues rich in phototoxins or the ability to detoxify these secondary substances. The cytochrome P-450 polysubstrate monooxygenase systems involved, the metabolic products, and a new putative toxin pump have been described. Dietary antioxidants (β-carotene, vitamin E, ascorbate) are additional defences against phototoxicity. They reduce mortality in herbivores exposed to phototoxins and some specialist herbivores have high constitutive levels. Adapted specialist insects also have higher constitutive levels of superoxide dismutase (SOD) and respond to phototoxins in their diet by the induction of catalase (CAT), glutathione reductase (GR), and increased levels of reduced glutathione (GSH). Artificial inhibition of the enzymes SOD and CAT had little effect on phototoxicity but inhibition of GSH synthesis in herbivores enhanced photooxidative effects of administered phototoxins on lipid peroxidation. While insects have many mechanisms to overcome plant photooxidants, the Asteraceae appear to have adopted a strategy of counterattack. We suggest and provide preliminary evidence that a second group of secondary substances, the sesquiterpene lactones, occurring in the Asteraceae can attack key antioxidant defences to synergise phototoxins.

Ethyl m-digallate from red maple, Acer rubrum L., as the major resistance factor to forest tent caterpillar, Malacosoma disstria Hbn.

An ethanolic extract of red maple (Acer rubrum L.) leaves (RME) applied to trembling aspen (Populus tremuloides Michx.) leaves reduced feeding in choice test assays with forest tent caterpillar larvae (Malacosoma disstria Hbn.) (FTC), whereas a trembling aspen foliage extract, similarly applied, stimulated feeding. Compounds isolated from the RME were gallic acid, methyl gallate, ethyl gallate, m-digallate, ethyl m-digallate, 1-O-galloyl-β-D-glucose, 1-O-galloyl-α-L-rhamnose, kaempferol 3-O-β-D-glucoside, kaempferol 3-O-β-D-galactoside, kaempferol 3-O-β-L-rhamnoside, kaempferol-3-O-rhamnoglucoside, quercetin 3-O-β-D-glucoside, quercetin 3-O-β-L-rhamnoside and quercetin 3-O-rhamnoglucoside, (−)-epicatechin, (+)-catechin and ellagic acid. All of the gallates, (−)-epicatechin, and kaempferol 3-O-β-L-rhamnoside deterred feeding on trembling aspen leaf disks when applied at 0.28 mg/cm2. The two digallates deterred feeding by 90% and were the most effective. HPLC analysis indicated that ethyl m-digallate is present in amounts 10–100 × higher in RME (∼2.5–250 mg/g) than any other compound. Thus, ethyl m-digallate appears to be the major compound protecting red maple from feeding by FTC, with a minor contribution from other gallates.

Accumulation of phototoxic thiophenes in Tagetes erecta (Asteraceae) elicited by Fusarium oxysporum

Abstract Infection of 2-week-old seedlings of Tagetes erecta var “Crackerjack” by Fusarium oxysporum Schl. f. sp. callistephi (Beach) Snyder et Hansen, race 2 (moderately virulent) and F. oxysporum Schl. f. sp. radicis-lycopersici Jarvis and Shoemacker (highly virulent), resulted in different patterns of thiophene kinetics in the infected tissues. The detected thiophenes 5-(4-hydroxy-1-butenyl)-2-2′-bithienyl (BBT-OH), 5-(4 acetoxy-1-butenyl)-2,2′-bithienyl (BBT-OAc) and alpha-terthienyl (α-T), accumulated in roots and stems which had been partially damaged by the moderate pathogen, reaching maximum concentrations 12 days after inoculation with up to 12 times the concentration in uninoculated control plants. However, severe infection with the highly virulent F. oxysporum strain resulted in a decline in thiophene levels in the damaged tissues. The naturally occurring thiophenes BBT-OH, BBT-OAc, α-T, 5-(3-buten-1-ynil)-2,2′-bithienyl (BBT) and 5-(3,4-diacetoxy-1-butinyl)-2, 2′-bithienyl (BBT-20Ac) completely inhibited in vitro spore germination of both fungi at a concentration of 5 μg ml−1 in the presence of near UV light (4 W m−2). α-T was strongly photo-toxic towards mycelial growth of both fungi in shake culture with an EC50 of 0·03 and 0·06 μg ml−1 for the highly virulent and the moderately virulent F. oxysporum strains, respectively. In the dark, only the latter strain was inhibited by high concentrations of the compound. Tritiated α-T was not significantly metabolized by F. oxysporum f. sp. radicis-lycopersici when grown in shake cultures containing 0·3 μg of 3H−α-T per millilitre. The role of thiophenes as phytoalexins is discussed in relation to these findings.

Mineral cycling in a tropical palm forest

Nutrient cycling and biomass characteristics of a tropical palm forest dominated byOrbignya cohune were found to be different from thsoe of hardwood dominated forests. The cohune palm forest had a high proportion of biomass in leaves (5%), a reduced sapling layer, a large amount of standing forest litter and an exceptionally low decomposition rate factor (0.1 year−1). Mineral concentrations in palm leaves were generally lower than in hardwood species with the exception of Na, which was exceptionally high inOrbignya cohune. Biomass was estimated at 226 tons ha−1 containing 1173 kg ha−1 N; 126 kg ha−1 P; 437 kg ha−1 K; 1869 kg ha−1 Mg; 125 kg ha−1 Ca, and 2177 kg ha−1 Na. Soils of cohune association did not differ significantly from those of neighbouring hardwood dominated associations with the exception of Na which occurred in higher concentration because of bioaccumulation in the dominant. The results suggest that the growth habits and physiology of a dominant can strongly influence some of the ecological parameters used to describe aforest association.

The Interaction of Selected Phytochemicals, HIV Drugs, and Commercial-Source Herbal Teas and Capsules with Human Cytochrome P450 3A4 and P-glycoprotein

Abstract As the popularity of natural health product (NHP) use increases, unfortunately, so does the frequency of cases reporting suspected adverse interactions. Adverse reactions associated with concomitant NHP-therapeutic use may result from competing interactions at the level of the key xenobiotic-biotransforming phase I enzyme cytochrome P450 3A4 (CYP3A4) or the membrane-bound ATP-dependent protein pump P-glycoprotein (P-gp). In this study, selected NHPs of interest to the HIV+ community were assessed for their ability to affect these two important mechanisms of drug disposition. Briefly, commercial-source teas and powdered extracts in capsule formulations were examined for their ability to inhibit CYP3A4-mediated metabolism of the coadministered reference substrate dibenzyl-fluorescein, and their ability to stimulate P-gp ATPase activity. Among the herbal capsules, it was found that aqueous extracts of two different goldenseal (Hydrastis canadensis. L.) products were the most inhibitory of CYP3A4-mediated metabolism among all NHPs tested (IC50: 3.03 and 3.23 mg/mL). Goldenseal and milk thistle [Silybum marianum. (L.) Gaertn.] teas were found to stimulate P-gp ATPase to a greater degree than the reference positive control verapamil (20 μ M). As well, 70% ethanol extracts of one goldenseal product (designated NRP 121) and aqueous extracts of another (designated NRP 17) had the highest relative P-gp ATPase activity overall. Milk thistle and goldenseal products were further analyzed for levels of their marker constituents by HPLC; silibinin and berberine in the experimental design were found to be at biologically relevant concentrations. High-throughput in vitro. studies such as the CYP3A4 inhibition and P-pg ATPase screening assays may help to determine which NHPs interact with drug disposition mechanisms, thus ensuring that the occurrence of adverse events due to competing interactions is minimized. They are useful for selecting specific NHPs, NHP formulations, phytochemicals, or drugs to be advanced to more detailed in vivo. experimental designs. Although the extrapolation of the current in vitro. findings to clinical effects may well be considered speculative, the overall in vitro. data should still be viewed as a signal of potential in vivo. interactions.