Elise Ivarsen

The effect of Artemisia annua on broiler performance, on intestinal microbiota and on the course of a Clostridium perfringens infection applying a necrotic enteritis disease model

The aerial parts of the plant Artemisia annua contain essential oils having antimicrobial properties against Clostridium perfringens Type A, the causal agent for necrotic enteritis in broilers. In two experiments, the influence of increasing dietary concentrations of dried A. annua leaves (0, 5, 10 and 20 g/kg) and n-hexane extract from fresh A. annua leaves (0, 125, 250 and 500 mg/kg) on broiler performance was investigated. Dried plant material decreased feed intake and body weight in a dose-dependent manner, and 10 and 20 g/kg diet tended to improve the feed conversion ratio. The n-hexane extract also reduced feed intake, but broiler weight tended to decrease only at the highest dietary concentration. The feed conversion ratio tended to improve when birds received 250 and 500 mg/kg n-hexane extract. In a third experiment, a necrotic enteritis disease model was applied to investigate the effect of the dietary addition of dried A. annua leaves (10 g/kg on top) or n-hexane extract of A. annua (250 mg/kg) on the severity of the disease in broilers. The addition of n-hexane extract reduced the intestinal C. perfringens numbers and the severity of the disease-related small intestinal lesions. Over the infection period from day 17 to day 27, birds supplemented with the n-hexane extract gained more weight than both the challenged control birds and birds receiving dried plant material. The results indicate that n-hexane extracts derived from A. annua can modulate the course of necrotic enteritis and compensate to a certain extent for the disease-associated weight losses.

Artemisinin production and precursor ratio in full grown Artemisia annua L. plants subjected to external stress

Abstrac tThe concentration of the lifesaving antimalarial compound artemisinin (AN) in cultivated Artemisia annua (A. annua) plants is relatively low, and thus research in improving the content is important. In the present study, external stress was applied to adult plants of A. annua and the effect was examined on the concentrations of AN and its immediate precursors in leaves, and these concentrations were related to densities and sizes of the glandular trichomes (GT). Plants were stress treated weekly five times by sandblasting or spraying with salicylic acid, chitosan oligosaccharide, H2O2, and NaCl solutions. Contents of AN-related compounds (AN-c) were analysed in leaf samples from an upper and a lower position of the plants, and GT were quantified and measured. In lower leaves, several stress treatments had significant negative effects on concentrations of AN-c, whereas the ratios between compounds showed an increased conversion to AN. In the upper leaves, no changes were observed compared to controls. Linear relations were found between the concentrations of metabolites and the density of GT in both upper and lower leaves, and size of GT in lower leaves. Results suggested that older and younger leaves may respond differently to applied stress. A part of the plants were infected by powdery mildew, and this caused significantly different compositions of the AN-c, compared to uninfected plants. In conclusion, changes in concentrations of AN-c seemed largely to be related to changes in GT densities and sizes.

Antihistomonal effects of artemisinin and Artemisia annua extracts in vitro could not be confirmed by in vivo experiments in turkeys and chickens

Five different Artemisia annua-derived materials (i.e. dry leaves, pure artemisinin, and hexane, dichloromethane or methanol extracts of leaves) were screened for their in vitro activities against six clonal cultures of Histomonas meleagridis. Except for the methanol extract, all tested materials displayed in vitro activity against all tested protozoal clones. Neither the dry plant material, extracts nor artemisinin showed any antibacterial activity against the xenic bacteria accompanying the six H. meleagridis clones at concentration levels identical to the antihistomonal setting. The dichloromethane extract of dry leaves (Ext-DCM) (minimal lethal concentration=1.0 mg/ml) and artemisinin (half-maximal inhibitory concentration=1.295 mg/ml) had the most promising antihistomonal properties and were therefore subsequently tested in a standardized experimental infection model in both turkeys and chickens infected with clonal H. meleagridis. There were no differences between treatment groups, where all infected turkeys showed severe clinical histomonosis and demonstrated severe typhlohepatitis typical for histomonosis. Consistent with the infection model used, the infected chickens did not show any adverse clinical signs but contracted severe lesions in their caeca 7 and 10 days post infection (d.p.i.), liver lesions were absent to mild after 7 d.p.i. and progressed to severe lesions at 10 d.p.i.; thus no differences between treatment groups were observed. In conclusion, neither artemisinin nor Ext-DCM was able to prevent experimental histomonosis in turkeys and chickens at the given concentrations, which is contrary to the antihistomonal effect noticed in vitro even though the same clonal culture was used. The results of this study therefore clearly demonstrate the importance of defined in vivo experimentation in order to assess and verify in vitro results.

Bioassay-guided chromatographic isolation and identification of antibacterial compounds from Artemisia annua L. that inhibit Clostridium perfringens growth

Clostridium perfringens is the causative agent of necrotic enteritis leading to significant losses in the poultry industry. Dichloromethane and n-hexane extracts of aerial parts of Artemisia annua (Asteraceae) exhibited activity against C. perfringens with minimum inhibitory concentrations (MIC) of 185 and 270 μg/mL, respectively. Bioassay-guided fractionation of the extracts gave several active fractions (MIC between 75 and 600 μg/mL). Investigations of the most active fractions resulted in the isolation and characterization of the polyacetylene ponticaepoxide (MIC between 100 and 200 μg/mL) and (+)-threo-(5E)-trideca-1,5-dien-7,9,11-triyne-3,4-diol (MIC between 400 and 800 μg/mL), the flavonols chrysosplenol D (MIC between 200 and 400 μg/mL) and casticin (slight inhibition at 800 μg/mL), and 2,4-dihydroxy-6-methoxyacetophenone (slight inhibition at 800 μg/mL). Also, the coumarin scopoletin and the sesquiterpene lactone artemisinin were isolated from active fractions but showed no inhibition of C. perfringens growth at 800 and 2000 μg/mL, respectively. Fractions containing essential oil components with camphor constituting >60% did not show inhibition of C. perfringens up to 1600 μg/mL. Extracts and some active fractions showed higher antibacterial effect than individual bioactive compounds, suggesting that synergistic effects may underlie the observed antibacterial effect. The present study adds new valuable information on the antibacterial effect of A. annua against C. perfringens.