Search results for "LEVULINIC ACID"
showing 10 items of 35 documents
Conversion of levulinic acid to γ-valerolactone over Zr-containing metal-organic frameworks: Evidencing the role of Lewis and Brønsted acid sites
2021
Zr-containing UiO-66 and MOF-808 are evaluated for converting levulinic acid (LA) into γ-valerolactone (GVL) through various routes: (i) Step-wise esterification of LA to n-butyl levulinate (nBuL) and Meerwein-Ponndorf-Verley (MPV) reduction to GVL; (ii) One-pot two-steps esterification with n-butanol followed by MPV reduction with sec-butanol; and (iii) direct conversion of LA into GVL through a tandem reaction. Selection of this multistep complex reaction evidences the participation of the different acid sites (Lewis or Brønsted) of the material in each individual step: Brønsted-induced acid sites catalyze esterification reaction efficiently, while Lewis acid sites are the preferred sites…
Low temperature conversion of levulinic acid into γ-valerolactone using Zn to generate hydrogen from water and nickel catalysts supported on sepiolite
2020
1 scheme, 2 tables, 7 figures.-- Supplementary material available.
Gamma-valerolactone from levulinic acid and its esters: Substrate and reaction media determine the optimal catalyst
2021
13 figures, 7 tables.-- © 2021. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0
Intensified oxidative and nitrosative stress following combined ALA-based photodynamic therapy and local hyperthermia in rat tumors.
2003
Oxidative stress-related changes in tumors upon localized hyperthermia (HT), 5-aminolevulinic acid-based photodynamic therapy (ALA-PDT) and their combination (ALA+HT) were examined after the observation that the antitumor effects of ALA-PDT could be significantly enhanced upon simultaneous application of HT. Rats bearing s.c. DS-sarcomas (0.6–1.0 ml) on the hind foot dorsum were anesthetized and underwent one of the following treatments: (i) ALA-PDT (375 mg/kg 5-ALA i.v.); (ii) localized HT, 43°C for 60 min; (iii) combined ALA-PDT and HT [=ALA+HT]. Appropriate control experiments were also performed. After treatment, tumors were excised and rapidly frozen for later analysis of nitrosative s…
Enhanced effects of aminolaevulinic acid-based photodynamic therapy through local hyperthermia in rat tumours.
2003
The possibility of enhancing aminolaevulinic acid (ALA)-based photodynamic therapy (PDT) by simultaneous application of localised hyperthermia (HT) was evaluated. Treatments of rat DS-sarcomas included: (i) control, (ii) ALA administration (375 mg kg(-1), i.p.), no illumination, (iii) 'nonthermal' illumination, (iv) ALA-PDT: that is, ALA administration, 'nonthermal' illumination, (v) localised HT, 43 degrees C, 60 min (vi) ALA-PDT+HT: ALA administration with full spectrum irradiation resulting in ALA-PDT and HT. Tumour volume was monitored for 90 days or until a target volume (3.5 ml) was reached. No differences were seen between the first three groups, with all tumours reaching the target …
Enantioselective Henry addition of methyl 4-nitrobutyrate to aldehydes. Chiral building blocks for 2-pyrrolidinones and other derivatives.
2010
A catalytic highly enantioselective Henry addition of methyl 4-nitrobutyrate to aldehydes using a Cu(II)-amino pyridine complex as catalyst is described. The products resulting from this reaction constitute a new, highly versatile family of chiral building blocks as a result of the presence of three different functional groups on the molecule. These products have been transformed into nonracemic chiral gamma-lactams, 5-hydroxy-5-substituted levulinic acid derivatives, and delta-lactones.
Cellular damage to human hepatocytes through repeated application of 5-aminolevulinic acid.
2003
Abstract Background/Aims : 5-Aminolevulinic acid (ALA), a precursor of porphyrins is used for photodynamic diagnosis and therapy within topical or systemic applications. A potential toxic effect on the human liver is of major interest and therefore we investigated the impact of a repeated application of ALA without illumination on cultures of human hepatocytes. Methods : After ALA treatment of hepatocytes in vitro the porphyrin synthesis, albumin secretion, liver-specific enzyme release, and malondialdehyde levels were determined. In order to reduce levels of reactive oxygen substances, mannitol and the antioxidant enzymes superoxide dismutase and catalase were supplemented. Results : Porph…
Effect of unbalanced diets on incorporation of δ-aminolevulinic acid into cytochrome P-450
1987
Abstract The in vivo syntheses of two liver microsomal cytochromes P-450 PB 3a , P-450 UT 50 [(1987) Eur. J. Biochem., submitted] ( M r 50 000, 52 000) have been estimated by measuring the specific activity 2 h after i.p. administration of δ-[ 3 H]aminolevulinic acid to male Sprague Dawley rats. The animals were fed either a standard rat chow (5% lard, 22% casein) or unbalanced diets (high lipid, 30% lard or low protein, 6% casein) with or without 50 ppm Phenoclor DP6. The high-lipid diet supported a more rapid body weight gain but had little impact on cytochrome P-450 content, expressed either per whole liver or per mg microsomal protein, and on the incorporation of the precursor into cyto…
Ablative fractional laser-assisted photodynamic therapy for lentigo maligna: a prospective pilot study.
2019
Background Lentigo maligna (LM) is an in‐situ form of melanoma carrying a risk of progression to invasive lentigo maligna melanoma (LMM). LM poses a clinical challenge, with subclinical extension and high recurrence rates after incomplete surgery. Alternative treatment methods have been investigated with varying results. Photodynamic therapy (PDT) with methylaminolaevulinate (MAL) has already proved promising in this respect. Objectives To investigate the efficacy of ablative fractional laser (AFL)‐assisted PDT with 5‐aminolaevulinic acid nanoemulsion (BF‐200 ALA) for treating LM. Methods In this non‐sponsored, prospective pilot study ten histologically verified LMs were treated with AFL‐as…
A randomized, intraindividual, non-inferiority, Phase III study comparing daylight photodynamic therapy with BF-200 ALA gel and MAL cream for the tre…
2018
Abstract Background The most effective treatment modality for actinic keratosis (AK) is photodynamic therapy (PDT). Major obstacles of PDT are the need of a special illumination device and pain accompanying the illumination. These issues may be overcome by replacing an artificial high‐power light source with natural daylight for more extended illumination at lower light doses. Objective To determine whether BF‐200 ALA (a nanoemulsion gel containing 7.8% 5‐aminolaevulinic acid) is non‐inferior to MAL (a cream containing 16% methyl‐aminolaevulinate) in the treatment of mild‐to‐moderate AK with daylight PDT (dPDT). Non‐inferiority of the primary efficacy variable (total lesion clearance rate p…