Anders Kjær

Effect of external stress on density and size of glandular trichomes in full-grown Artemisia annua, the source of anti-malarial artemisinin

The experiments demonstrate that stress treatments to large Artemisia annua plants have a minor promoting effect on the initiation of glandular trichomes in developing leaves, and a maturing effect on glandular trichomes later in the life time of the individual trichome.

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.

Prediction of Starch, Soluble Sugars and Amino Acids in Potatoes ( Solanum tuberosum L.) Using Hyperspectral Imaging, Dielectric and LF-NMR Methodologies

Handling and processing of potatoes is performed in increasingly large and more automated facilities, and the industry calls for more automated machinery for quality assessment and sorting by concentration of starch, soluble sugars, protein, amino acids etc. of the potato tubers. The present study was designed to evaluate five different scanning methods for their potential use in potato assessment and sorting. Two methods were based on hyperspectral imaging, two were based on dielectric/bio-impedance and one was based on low-field nuclear magnetic resonance. A set of 60 potatoes of 10 different cultivars were simultaneously sampled for analyses of content and scanned by the five different scanning methods. The resulting multivariate dataset was used to estimate the prediction ability of the individual scanning methods on starch-related parameters, selected simple sugars, selected amino acids, conductivity of pressed cell sap and cell sizes. Results showed that most types of spectral analyses had relatively high potential for predicting the starch-related parameters and medium potential for predicting the concentration of the reducing sugars fructose and glucose. Most methods showed medium potential for prediction of several amino acids, including asparagine, which showed particularly promising predictions in the hyperspectral analyses of intact potatoes. The presented screening study enabled us to perform robust choices for the further development and optimization of the methods and instruments for industrial implementation.

Volatile organic compounds as markers of quality changes during the storage of wild rocket

The quality of leafy green vegetables changes during storage. Leaves become yellow or disintegrate, and an off-odor may develop. In addition, small amounts of volatile organic compounds (VOCs) are released. In this study, the release of acetone, carbon disulfide, dimethyl sulfide, nitromethane, pentane, 3-methylfuran, 2-ethylfuran, and dimethyl disulfide from wild rocket with different initial qualities was monitored during 8d storage at 10°C and correlated to aerobic bacteria counts, yeast and mold counts, and degree of tissue disintegration. The release of VOCs, except for 3-methylfuran, was influenced by the initial quality of the leaves. The release of pentane and 2-ethylfuran was related to the degree of tissue disintegration, and the release of dimethyl sulfide and dimethyl disulfide was related to the total aerobic bacteria count. The results demonstrated that VOCs can be used as markers for monitoring the complex quality changes taking place in packaged fresh produce during storage.

Detection of Glycoalkaloids and Chlorophyll in Potatoes (Solanum tuberosum L.) by Hyperspectral Imaging

The purpose of the study was to investigate the use of hyperspectral imaging (HSI) to detect and quantify chlorophyll (Chl) and total glycoalkaloid concentrations (TGA) in potatoes. To create a set of tubers with different concentrations of Chl and TGA, potatoes of four varieties were wounded or treated with red, blue, red/blue, UV-a, UV-b or UV-c light. HSI analyses were performed with a reflection based setup implemented in an industrial potato sorting machine. After hyperspectral analyses, the peel was sampled, and concentrations of Chl and total TGA were determined. Results showed that the HSI system predicted the concentrations of Chl with a relatively high degree of accuracy, and a prediction R2 value of 0.92. Prediction of TGA concentrations performed to a much lesser extent, and the overall prediction R2 value was only 0.21. Moderate soil covers only affected the prediction powers to a minor degree.ResumenEl propósito del estudio fue investigar el uso de imagen hiperespectral (HSI) para detectar y cuantificar clorofila (Chl) y concentraciones totales de glicoalcaloides (TGA) en papa. Para crear un grupo de tubérculos con diferentes concentraciones de Chl y TGA, se hirieron cuatro variedades de papa o se trataron con luz roja, azul, roja/azul, UV-a, UV-b, o UV-c. Los análisis de HSI se hicieron con una instalación basada en reflección implementada en un maquina industrial seleccionadora de papa. Después de los análisis hiperespectrales, se muestreó la cáscara, y se determinaron concentraciones de Chl y TGA totales, Los resultados mostraron que el sistema HSI predijo las concentraciones de Chl con relativamente alto grado de precisión y con un valor de predicción R2 de 0.92. Se hizo la predicción de las concentraciones de TGA a menor escala, y la predicción general del valor R2 fue solo de 0.21. Las cubiertas moderadas de suelo solo afectaron los poderes de predicción en un menor grado.

Trichomes in Artemisia annua : Initiation, Development, Maturation and the Possibilities to Influence these Factors

The glandular trichomes (GT) of Artemisia annua (A. annua) synthesize and store the antimalarial compound artemisinin (AN) and several hundreds of other secondary metabolites (SM), and from an economical viewpoint, the GT are the most important structures of the plants. This chapter will give an overview of the contemporary knowledge on the morphology of the GT, the mechanisms of initiation of GT, the development and maturation processes of GT and an overview of the current research on elucidating the effect of the application or change in external factors on the density and size of GT in A. annua.

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.

Noninvasive Determination of Firmness and Dry Matter Content of Stored Onion Bulbs Using Shortwave Infrared Imaging with Whole Spectra and Selected Wavelengths

A firm texture of dry onions is important for consumer acceptance. Both the texture and dry matter content decline during storage, influencing the market value of onions. The main goal of this study was to develop predictive models that in future might form the basis for automated sorting of onions for firmness and dry matter content in the industry. Hyperspectral scanning was conducted in reflectance mode for six commercial batches of onions that were monitored three times during storage. Mean spectra from the region of interest were extracted and partial least squares regression (PLSR) models were constructed. Feature wavelengths were identified using variable selection techniques resulting from interval partial least squares and recursive partial least squares analyses. The PLSR model for firmness gave a root mean square error of cross-validation (RMSECV) of 0.84 N, and a root mean square error of prediction (RMSEP) of 0.73 N, with coefficients of determination (R2) of 0.72 and 0.83, respectively. The RMSECV and RMSEP of the PLSR model for dry matter content were 0.10% and 0.08%, respectively, with a R2 of 0.58 and 0.79, respectively. The whole wavelength range and selected wavelengths showed nearly similar results for both dry matter content and firmness. The results obtained from this study clearly reveal that hyperspectral imaging of onion bulbs with selected wavelengths, coupled with chemometric modeling, can be used for the noninvasive determination of the firmness and dry matter content of stored onion bulbs.