RESUMEN
Massetolide A is a cyclic lipopeptide (CLP) antibiotic produced by various Pseudomonas strains from diverse environments. Cloning, sequencing, site-directed mutagenesis, and complementation showed that massetolide A biosynthesis in P. fluorescens SS101 is governed by three nonribosomal peptide synthetase (NRPS) genes, designated massA, massB, and massC, spanning approximately 30 kb. Prediction of the nature and configuration of the amino acids by in silico analysis of adenylation and condensation domains of the NRPSs was consistent with the chemically determined structure of the peptide moiety of massetolide A. Structural analysis of massetolide A derivatives produced by SS101 indicated that most of the variations in the peptide moiety occur at amino acid positions 4 and 9. Regions flanking the mass genes contained several genes found in other Pseudomonas CLP biosynthesis clusters, which encode LuxR-type transcriptional regulators, ABC transporters, and an RND-like outer membrane protein. In contrast to most Pseudomonas CLP gene clusters known to date, the mass genes are not physically linked but are organized in two separate clusters, with massA disconnected from massB and massC. Quantitative real-time PCR analysis indicated that transcription of massC is strongly reduced when massB is mutated, suggesting that these two genes function in an operon, whereas transcription of massA is independent of massBC and vice versa. Massetolide A is produced in the early exponential growth phase, and biosynthesis appears not to be regulated by N-acylhomoserine lactone-based quorum sensing. Massetolide A production is essential in swarming motility of P. fluorescens SS101 and plays an important role in biofilm formation.
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Antibacterianos/biosíntesis , Proteínas Bacterianas/genética , Péptido Sintasas/genética , Péptidos Cíclicos/biosíntesis , Pseudomonas fluorescens/fisiología , Antibacterianos/química , Proteínas Bacterianas/metabolismo , Biopelículas/crecimiento & desarrollo , Clonación Molecular , Elementos Transponibles de ADN , ADN Bacteriano/química , ADN Bacteriano/genética , Perfilación de la Expresión Génica , Regulación Bacteriana de la Expresión Génica , Prueba de Complementación Genética , Locomoción , Familia de Multigenes , Mutagénesis Insercional , Operón , Péptido Sintasas/metabolismo , Péptidos Cíclicos/química , Pseudomonas fluorescens/genética , ARN Bacteriano/biosíntesis , ARN Mensajero/biosíntesis , Análisis de Secuencia de ADNRESUMEN
Antioxidative properties of Geranium macrorrhizum, Potentilla fruticosa and Rosmarinus officinalis (as a reference) extracts were evaluated in Dutch style fermented sausages. Extracts were incorporated into sausages during preparation. The sausages were subsequently fermented, tested and compared to a standard spices mix, traditionally used for the production of such sausages. Formation of the primary oxidation products - peroxides, and secondary - TBARS and hexanal was monitored. The polar extracts from Potentilla showed some antioxidant activity, especially in combination with ascorbate, however the activity was low compared to the standard spices mix. Polar extracts from Geranium showed only negligible antioxidant activity.
RESUMEN
This study reports the development and validation of a model-based, 3D patient dose reconstruction method for pre-treatment quality assurance using EPID images. The method is also investigated for sensitivity to potential MLC delivery errors. Each cine-mode EPID image acquired during plan delivery was processed using a previously developed back-projection dose reconstruction model providing a 3D dose estimate on the CT simulation data. Validation was carried out using 24 SBRT-VMAT patient plans by comparing: (1) ion chamber point dose measurements in a solid water phantom, (2) the treatment planning system (TPS) predicted 3D dose to the EPID reconstructed 3D dose in a solid water phantom, and (3) the TPS predicted 3D dose to the EPID and our forward predicted reconstructed 3D dose in the patient (CT data). AAA and AcurosXB were used for TPS predictions. Dose distributions were compared using 3%/3 mm (95% tolerance) and 2%/2 mm (90% tolerance) γ-tests in the planning target volume (PTV) and 20% dose volumes. The average percentage point dose differences between the ion chamber and the EPID, AcurosXB, and AAA were 0.73 ± 1.25%, 0.38 ± 0.96% and 1.06 ± 1.34% respectively. For the patient (CT) dose comparisons, seven (3%/3 mm) and nine (2%/2 mm) plans failed the EPID versus AAA. All plans passed the EPID versus Acuros XB and the EPID versus forward model γ-comparisons. Four types of MLC sensitive errors (opening, shifting, stuck, and retracting), of varying magnitude (0.2, 0.5, 1.0, 2.0 mm), were introduced into six different SBRT-VMAT plans. γ-comparisons of the erroneous EPID dose and original predicted dose were carried out using the same criteria as above. For all plans, the sensitivity testing using a 3%/3 mm γ-test in the PTV successfully determined MLC errors on the order of 1.0 mm, except for the single leaf retraction-type error. A 2%/2 mm criteria produced similar results with two more additional detected errors.
Asunto(s)
Imagenología Tridimensional/métodos , Modelación Específica para el Paciente , Planificación de la Radioterapia Asistida por Computador/métodos , Radioterapia de Intensidad Modulada/métodos , Humanos , Imagenología Tridimensional/instrumentación , Imagenología Tridimensional/normas , Fantasmas de Imagen , Planificación de la Radioterapia Asistida por Computador/instrumentación , Planificación de la Radioterapia Asistida por Computador/normasRESUMEN
PURPOSE: Radiation treatments have become increasingly more complex with the development of volumetric modulated arc therapy (VMAT) and the use of stereotactic body radiation therapy (SBRT). SBRT involves the delivery of substantially larger doses over fewer fractions than conventional therapy. SBRT-VMAT treatments will strongly benefit from in vivo patient dose verification, as any errors in delivery can be more detrimental to the radiobiology of the patient as compared to conventional therapy. Electronic portal imaging devices (EPIDs) are available on most commercial linear accelerators (Linacs) and their documented use for dosimetry makes them valuable tools for patient dose verification. In this work, the authors customize and validate a physics-based model which utilizes on-treatment EPID images to reconstruct the 3D dose delivered to the patient during SBRT-VMAT delivery. METHODS: The SBRT Linac head, including jaws, multileaf collimators, and flattening filter, were modeled using Monte Carlo methods and verified with measured data. The simulation provides energy spectrum data that are used by their "forward" model to then accurately predict fluence generated by a SBRT beam at a plane above the patient. This fluence is then transported through the patient and then the dose to the phosphor layer in the EPID is calculated. Their "inverse" model back-projects the EPID measured focal fluence to a plane upstream of the patient and recombines it with the extra-focal fluence predicted by the forward model. This estimate of total delivered fluence is then forward projected onto the patient's density matrix and a collapsed cone convolution algorithm calculates the dose delivered to the patient. The model was tested by reconstructing the dose for two prostate, three lung, and two spine SBRT-VMAT treatment fractions delivered to an anthropomorphic phantom. It was further validated against actual patient data for a lung and spine SBRT-VMAT plan. The results were verified with the treatment planning system (TPS) (ECLIPSE AAA) dose calculation. RESULTS: The SBRT-VMAT reconstruction model performed very well when compared to the TPS. A stringent 2%/2 mm χ-comparison calculation gave pass rates better than 91% for the prostate plans, 88% for the lung plans, and 86% for the spine plans for voxels containing 80% or more of the prescribed dose. Patient data were 86% for the lung and 95% for the spine. A 3%/3 mm χ-comparison was also performed and gave pass rates better than 93% for all plan types. CONCLUSIONS: The authors have customized and validated a robust, physics-based model that calculates the delivered dose to a patient for SBRT-VMAT delivery using on-treatment EPID images. The accuracy of the results indicates that this approach is suitable for clinical implementation. Future work will incorporate this model into both offline and real-time clinical adaptive radiotherapy.
Asunto(s)
Radiocirugia/métodos , Planificación de la Radioterapia Asistida por Computador/métodos , Radioterapia de Intensidad Modulada/métodos , Algoritmos , Vértebras Cervicales/efectos de la radiación , Simulación por Computador , Humanos , Pulmón/efectos de la radiación , Pulmón/cirugía , Masculino , Modelos Teóricos , Método de Montecarlo , Fantasmas de Imagen , Próstata/efectos de la radiación , Radiometría/instrumentación , Radiometría/métodos , Radiocirugia/instrumentación , Dosificación Radioterapéutica , Planificación de la Radioterapia Asistida por Computador/instrumentación , Radioterapia de Intensidad Modulada/instrumentación , Recto/efectos de la radiación , Tomografía Computarizada por Rayos XRESUMEN
The ability of several white-rot fungal strains to remove and detoxify acetone extractives (pitch or resin) in Scots pine sapwood was investigated in stationary laboratory batch assays. Fungal pretreatment provided up to 62% total pitch reduction and significant decreases in pitch toxicity. The best strains were Bjerkandera sp. strain Stereum hirsutum and Trametes versicolor that eliminated over 93% of the problematic triglyceride fraction and 58-87% of other lipophilic extractive classes in only 2 weeks. Fungal removal of the wood extractives was accompanied by a 7.4-16.9-fold decrease in their inhibitory effect, as determined in the Microtox bioassay. Wood pretreatment by Bjerkandera sp. and T. versicolor caused limited losses of woody mass (less than 4% in 4 weeks); whereas S. hirsutum led to somewhat higher mass losses (7% in 4 weeks). These results indicate the potential of white rot fungi to control pitch deposition problems in pulping and to reduce the aquatic toxicity caused by naturally-occurring lipophilic extractives in forest industry effluents.
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Acetona/metabolismo , Hongos/metabolismo , Resinas de Plantas/metabolismo , Árboles/microbiología , Biotecnología/métodos , Pared Celular/metabolismo , Ácidos Grasos/metabolismo , Esteroles/metabolismo , Triglicéridos/metabolismo , Contaminantes del Agua/metabolismoRESUMEN
The needles of several yew species and cultivars were analysed by high-pressure liquid chromatography for paclitaxel, 10-deacetylpaclitaxel, cephalomannine, baccatin III, 10-deacetylbaccatin III and brevifoliol. About 750 samples were collected from five different locations in the Netherlands and the UK. The results of this screening show a large variation in taxane content between the different species and cultivars. The content of paclitaxel and 10-deacetylbaccatin III varied from 0 to 500 micrograms/g and 0 to 4800 micrograms/g dried needles, respectively. Brevifoliol was found in a very high concentration in Taxus brevifolia. 10-Deacetylpaclitaxel, cephalomannine and baccatin III were found in concentrations ranging from 0 to 500 micrograms/g dried needles.
Asunto(s)
Antineoplásicos Fitogénicos/análisis , Paclitaxel/análisis , Árboles/química , Cromatografía Líquida de Alta Presión , Paclitaxel/análogos & derivados , Hojas de la Planta/química , Especificidad de la EspecieRESUMEN
A chromatographic procedure for the preparative isolation of six different 6-alkylsalicylic acids (syn. ginkgolic acids) with as alkyl substituents C13:0, C15:0, C15:1, C17:1, C17:2 and, tentatively C17:3 from Ginkgo biloba leaves was developed. The procedure consisted of a combination of normal-phase, reversed-phase and argentation chromatography. The compounds were characterised by means of UV, 1H-NMR and 13C-NMR spectroscopy, and mass spectrometry after silylation. A 15 cm C18 RP-HPLC column connected in series with a 20 cm silver(I) loaded cation exchanger HPLC column in combination with the solvent methanol-water (93:7) acidified with 0.1% formic acid was capable of separating the ginkgolic acids C13:0, C15:1, C17:2, C15:0 and C17:1 within 21 min on an analytical scale. The separation is based on a combination of reversed-phase mechanisms and double bond complexation. Detection took place by UV at 311 nm. The separation is a good starting point for the development of a quantitative procedure for the five major ginkgolic acids in Ginkgo leaves and standardised extracts.
Asunto(s)
Cromatografía Líquida de Alta Presión/métodos , Ginkgo biloba/química , Salicilatos/aislamiento & purificación , Cromatografía por Intercambio Iónico/métodos , Análisis EspectralRESUMEN
Two methods for the on-line detection in HPLC eluates of analytes possessing radical scavenging activity were improved and compared. The instrumental set-up of the method that is based on on-line inhibition of luminol chemiluminescence (CL) by antioxidants was improved using better quality syringe pumps, employing a diode array detector, and introducing a mixing/neutralisation coil and a pulse damper. Sensitivity of the HPLC-CL detection increased by a factor of 4. Post-column neutralisation of eluates improved compatibility of this detection method with acidified HPLC eluents. The second method, which is based on the post-column quenching of 2,2'-diphenyl-1-picrylhydrazyl radical (DPPH*), was improved by readjusting composition and flow-rate of the reagent, mounting an additional pulse damper and detecting unreacted DPPH* with a detector equipped with a tungsten lamp. Purging of the DPPH* solution with He gas prior to analysis was introduced. This led to 30-fold better detection limits. The improved methods were compared with respect to limits of detection, the radical scavenging mechanism involved, compatibility with common HPLC solvents and pH range, and some technical aspects. The techniques described have high potential for the rapid identification of radical scavengers in complex samples like plant extracts.
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Antioxidantes/análisis , Cromatografía Líquida de Alta Presión/métodos , Concentración de Iones de Hidrógeno , Mediciones Luminiscentes , Sensibilidad y Especificidad , Espectrofotometría UltravioletaRESUMEN
From the stembark of Tabernaemontana crassa the alkaloid ibogaine was isolated as the major component. Ibogaine showed activity against the gram-positive Bacillus subtilis. Conopharyngine was identified as one of the minor compounds.
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Alcaloides/aislamiento & purificación , Ibogaína/aislamiento & purificación , Plantas Medicinales/análisis , Alcaloides/farmacología , Bacterias/efectos de los fármacos , Fenómenos Químicos , Química , Cromatografía en Capa Delgada , Ibogaína/farmacología , Pruebas de Sensibilidad MicrobianaRESUMEN
A review is given of the literature on the antimicrobial activity of various indole alkaloids. The data are briefly discussed. A screening was performed of a series of plants belonging to the indole alkaloid rich plant families Apocynaceae and Loganiaceae, 25 materials representing 14 Apocynaceae species and 54 materials representing 41 Strychnos species were investigated. No activity against the yeast or the fungus, used as test organisms was found. A number of extracts showed activity against the gram-positive test organisms, 4 species showed activity against gram-negative bacteria.
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Antiinfecciosos , Plantas Medicinales , Alcaloides/farmacología , Antibacterianos , Bacterias/efectos de los fármacos , Medios de Cultivo , Indoles/farmacología , Pruebas de Sensibilidad MicrobianaRESUMEN
The taxonomy, phytochemistry, ethnobotany, and pharmacology of the genus Tabernaemontana L. (Apocynaceae) is reviewed. The genus is currently being revised taxonomically; most of the segregate genera are being reunited with it and the number of species that will ultimately be recognized will probably be about 100. All the names encountered in the chemical and ethnobotanical literature have been evaluated as far as possible, and a list is presented of the recognized species and their synonyms. The biogenesis and classification of the indole alkaloids found in Tabernaemontana species is set out and some problems in the determination of their stereochemistry are discussed. To facilitate access to the information, three lists have been compiled: the alkaloids in alphabetical order; the alkaloids in order of increasing molecular weight; and the alkaloids grouped according to their biogenetic classification, together with the species and plant part(s) in which they are known to occur. Biogenetic and chemotaxonomic aspects are briefly considered. A table of the non-alkaloidal constituents is also included. The ethnobotany of individual Tabernaemontana species is outlined and an overall assessment made. Likewise, information on the pharmacology of crude extracts and individual alkaloids from Tabernaemontana species has been assembled and appraised.
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Plantas Medicinales , Alcaloides/biosíntesis , Animales , Botánica , Fenómenos Químicos , Química , Humanos , Medicina Tradicional , Extractos Vegetales/farmacología , Plantas Medicinales/clasificación , Plantas TóxicasRESUMEN
Needles from a series of wild yews (Taxus baccata L.) from Sardinia were investigated for their contents of 10-deacetyl baccatin III (DAB-III, 1), paclitaxel (Taxol) (2) and taxine (3). Despite a common geographical origin, ample variation of the taxoid profile was discovered, and several samples were surprisingly devoid of all terpenoid markers above. This finding is unprecedented within the European yew, while the general lack of taxine might rationalize the observation that most plants investigated are actively and impunently browsed by goats.
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Antineoplásicos Fitogénicos/química , Fitoterapia , Extractos Vegetales/química , Taxus , Alcaloides/química , Altitud , Cromatografía Líquida de Alta Presión , Humanos , Italia , Paclitaxel/química , Hojas de la Planta , Suelo , Taxoides/químicaRESUMEN
The aim of this work is to describe and validate a new general research tool that performs Monte Carlo (MC) simulations for volumetric modulated arc therapy (VMAT) and dynamic intensity modulated radiation therapy (DIMRT), simultaneously tracking dose deposition in both the patient CT geometry and an arbitrary planar detector system. The tool is generalized to handle either entrance or exit detectors and provides the simulated dose for the individual control-points of the time-dependent VMAT and DIMRT deliveries. The MC simulation tool was developed with the EGSnrc radiation transport. For the individual control point simulation, we rotate the patient/phantom volume only (i.e. independent of the gantry and planar detector geometries) using the gantry angle in the treatment planning system (TPS) DICOM RP file such that each control point has its own unique phantom file. After MC simulation, we obtained the total dose to the phantom by summing dose contributions for all control points. Scored dose to the sensitive layer of the planar detector is available for each control point. To validate the tool, three clinical treatment plans were used including VMAT plans for a prostate case and a head-and-neck case, and a DIMRT plan for a head-and-neck case. An electronic portal imaging device operated in 'movie' mode was used with the VMAT plans delivered to cylindrical and anthropomorphic phantoms to validate the code using an exit detector. The DIMRT plan was delivered to a novel transmission detector, to validate the code using an entrance detector. The total MC 3D absolute doses in patient/phantom were compared with the TPS doses, while 2D MC doses were compared with planar detector doses for all individual control points, using the gamma evaluation test with 3%/3 mm criteria. The MC 3D absolute doses demonstrated excellent agreement with the TPS doses for all the tested plans, with about 95% of voxels having γ <1 for the plans. For planar dosimetry image comparisons, we defined an acceptable pass rate of >90% of percentage pixels with γ <1. We found that over 90% of control points in the plans passed this criterion. In general, our results indicate that the simulation tool is suitable for accurately calculating both patient/phantom doses and planar doses for VMAT dose delivery. The tool will be valuable to check performance and advance the development of in vivo planar detectors for use in measurement-based VMAT dose verification. In addition, the tool can be useful as an independent research tool for VMAT commissioning of the TPS and delivery system.
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Método de Montecarlo , Radioterapia de Intensidad Modulada/métodos , Humanos , Fantasmas de Imagen , Dosificación Radioterapéutica , Reproducibilidad de los ResultadosRESUMEN
Observations by the Mars Science Laboratory Mast Camera (Mastcam) in Gale crater reveal isolated outcrops of cemented pebbles (2 to 40 millimeters in diameter) and sand grains with textures typical of fluvial sedimentary conglomerates. Rounded pebbles in the conglomerates indicate substantial fluvial abrasion. ChemCam emission spectra at one outcrop show a predominantly feldspathic composition, consistent with minimal aqueous alteration of sediments. Sediment was mobilized in ancient water flows that likely exceeded the threshold conditions (depth 0.03 to 0.9 meter, average velocity 0.20 to 0.75 meter per second) required to transport the pebbles. Climate conditions at the time sediment was transported must have differed substantially from the cold, hyper-arid modern environment to permit aqueous flows across several kilometers.
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As radiation treatment delivery becomes more complex, including dynamic IMRT and VMAT, the argument for routine patient dose verification becomes more compelling. This work demonstrates a technique that utilizes our pre-existing portal dose image prediction algorithm to compute 3D patient dose from recorded on-treatment portal images. This approach can be applied on CT simulation data or daily cone-beam CT data sets. Here we demonstrate the robustness of our dose reconstruction technique with phantom and patient examples, with delivery schemes including IMRT and VMAT. For an example prostate treatment site, 3D dose distributions reconstructed in the patient model are computed for each fraction, and DVHs presented. Results indicate that the patient dose reconstruction algorithm compares well with treatment planning system computed doses for controlled test situations. For patient examples the 3D chi comparison values (similar to the gamma comparison) ranged from 94.5% to 100% agreement for voxels > 10% maximum dose for all treatments and phantom cases. We show an example where the DVH for fraction nine of a prostate treatment fails acceptability criteria, due to a previously unnoticed positioning error. Future work involves building our patient dose reconstruction into a QA package, subsequently integrating it into a clinical workflow. We are also investigating the use of this tool as a backbone for an in-house adaptive radiotherapy implementation. This work is supported by Varian Medical Systems.
RESUMEN
Dosimetric verification of patient treatment plans has become increasingly important due to the widespread use of complicated delivery techniques. IMRT and VMAT treatments are typically verified prior to start of the patient's course of treatment, using a point dose and/or a film measurement. Pre-treatment verification will not detect patient or machine-related errors; therefore, in vivo dosimetric verification is the only way to determine if the patient's treatment was delivered correctly. Portal images were acquired throughout the course of five prostate and six head-and-neck patient IMRT treatments. The corresponding predicted images were calculated using a previously developed portal dose image prediction algorithm, which combines a versatile fluence model with a patient scatter and EPID dose prediction model. The prostate patient image agreement was found to vary day-to-day due to rectal gas pockets and the effect of adjustable support rails on the patient couch. The head-and-neck patient images were observed to be more consistent daily, but an increased measured dose was evident at the periphery of the patient, likely due to patient weight loss. The majority of the fields agreed within 3% and 3 mm for greater than 90% of the pixels, as established by the χ-comparison. This work demonstrates the changes in patient anatomy that are detectable with the portal dose image prediction model. Prior to clinical implementation, the effect of the couch must be incorporated into the model, the image acquisition must be automatically scheduled and routine EPID QA must be undertaken to ensure the collection of high-quality EPID images.
RESUMEN
Hormone and veterinary drug screening and forensics can benefit from the recent developments in desorption electrospray ionisation (DESI) mass spectrometry (MS). In this work the feasibility of DESI application has been studied. Using a linear ion trap or quadrupole time-of-flight (TOF) MS instrument both full-scan and data-dependent collision-induced dissociation MS(n) spectra were acquired in seconds without sample preparation. Preliminary data are presented for the rapid screening of (pro)hormone supplement samples, an illegal steroid cocktail and forensic samples from veterinary drug investigations. The potential of this DESI approach is clearly demonstrated since compounds observed could be independently confirmed by liquid chromatography/TOFMS with accurate mass measurement, and/or proton nuclear magnetic resonance spectroscopy. Specific concerns related to false-positive and false-negative findings due to limitations in quantification and memory-effects are briefly discussed. It is envisaged that DESI will achieve a prominent role in hormone and veterinary drug analysis in the near future.
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Hormonas/análisis , Espectrometría de Masa por Ionización de Electrospray/métodos , Esteroides/análisis , Detección de Abuso de Sustancias/métodos , Drogas Veterinarias/análisis , Animales , Bovinos , Crimen , Ciencias ForensesRESUMEN
A nonselected group of 45 patients was treated for the purpose of curing a carcinoma of the esophagus, only by irradiation using a 360 degrees rotation irradiation technique. Twenty-one patients were treated with a 220kV X-ray beam and 24 patients with a telecobalt gamma-ray beam. The 2-year survival rate was 11%. The 2- and 5-year survival rate was better in the group of patients who were treated with telecobalt gamma-rays, than in the group treated with 220-kV X-rays. No differences were found in local cure between the 2 groups of patients. No improvement can be expected with increase of tumour dose above 60 Gy (6000 rad) on the 80%-isodose line. Up till now the rotation irradiation with Co-60 in the treatment of a carcinoma of the esophagus remains one of the most simple and adequate irradiation techniques.
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Radioisótopos de Cobalto/uso terapéutico , Neoplasias Esofágicas/radioterapia , Teleterapia por Radioisótopo/métodos , Anciano , Femenino , Humanos , Masculino , Dosificación Radioterapéutica , RotaciónRESUMEN
A method has been developed for the quantitation of the bitter component limonin in grapefruit juice and other citrus juices. The sample clean-up consisted of centrifugation, filtration and a selective, rapid and reproducible purification with a C2 solid-phase extraction column. The limonin concentration was determined by high-performance liquid chromatography on a C18 column with UV detection at 210 nm. A linear response was obtained from 0.0 to 45 ppm limonin. The minimum detectable amount was 2 ng. The minimum concentration which was detected without concentration with good precision was 0.1 ppm. The method was also used for the determination of limonin in different types of oranges, including navel oranges, mandarins, lemons, limes, pomelos and uglis.
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Bebidas/análisis , Citrus/análisis , Limoninas , Triterpenos/análisis , Fenómenos Químicos , Química , Cromatografía Líquida de Alta Presión , Espectrofotometría UltravioletaRESUMEN
The concentrations of ginkgolides A, B, and C, and bilobalide were determined in the leaves of 3 different Dutch GINKGO BILOBA trees from late spring until late autumn 1990. The concentration versus harvest time plots were roughly the same for all the compounds in each of the 3 trees. Concentration was lowest in spring and then gradually increased until a maximum in late summer or early autumn was reached. Thereafter the concentration declined until leaf fall. The difference in ginkgolide and bilobalide content between the 3 trees was very high. For ginkgolide B, the pharmacologically most potent compound, the maximum concentration was less than 3, 68 and 204 ppm respectively. Possible reasons for these differences and consequences for phytotherapy are discussed briefly.