AL Extracts Research Articles

Development and characterization of a prototypic pan-amyloid clearing agent - a novel murine peptide-immunoglobulin fusion.

Systemic amyloidosis is a progressive disorder characterized by the extracellular deposition of amyloid fibrils and accessory proteins in visceral organs and tissues. Amyloid accumulation causes organ dysfunction and is not generally cleared by the immune system. Current treatment focuses on reducing amyloid precursor protein synthesis and slowing amyloid deposition. However, curative interventions will likely also require removal of preexisting amyloid deposits to restore organ function. Here we describe a prototypic pan-amyloid binding peptide-antibody fusion molecule (mIgp5) that enhances macrophage uptake of amyloid. The murine IgG1-IgG2a hybrid immunoglobulin with a pan amyloid-reactive peptide, p5, fused genetically to the N-terminal of the immunoglobulin light chain was synthesized in HEK293T/17 cells. The binding of the p5 peptide moiety was assayed using synthetic amyloid-like fibrils, human amyloid extracts and amyloid-laden tissues as substrates. Binding of radioiodinated mIgp5 with amyloid deposits in vivo was evaluated in a murine model of AA amyloidosis using small animal imaging and microautoradiography. The bioactivity of mIgp5 was assessed in complement fixation and in vitro phagocytosis assays in the presence of patient-derived amyloid extracts and synthetic amyloid fibrils as substrates and in the presence or absence of human serum. Murine Igp5 exhibited highly potent binding to AL and ATTR amyloid extracts and diverse types of amyloid in formalin-fixed tissue sections. In the murine model of systemic AA amyloidosis, 125I-mIgp5 bound rapidly and specifically to amyloid deposits in all organs, including the heart, with no evidence of non-specific uptake in healthy tissues. The bioactivity of the immunoglobulin Fc domain was uncompromised in the context of mIgp5 and served as an effective opsonin. Macrophage-mediated uptake of amyloid extract and purified amyloid fibrils was enhanced by the addition of mIgp5. This effect was exaggerated in the presence of human serum coincident with deposition of complement C5b9. Immunostimulatory, amyloid-clearing therapeutics can be developed by incorporating pan-amyloid-reactive peptides, such as p5, as a targeting moiety. The immunologic functionality of the IgG remains intact in the context of the fusion protein. These data highlight the potential use of peptide-antibody fusions as therapeutics for all types of systemic amyloidosis.

Larvicidal and repellent potential of Ageratum houstonianum against Culex pipiens.

Mosquitoes are unquestionably the most medic arthropod vectors of disease.Culex pipiens, usually defined as a common house mosquito, is a well-known carrier of several virus diseases. Crude ethanol extracts of different organs ofAgratum houstonianumare tested withCulex pipiensLinnaeus (Diptera: Culicidae) to determine their larvicidal, antifeedant, and repellency effects. Alongside biochemical analysis, the activity of the AChE, ATPase, CarE, and CYP-450 is detected in the total hemolymph of theC. pipienslarvae to examine the enzymatic action on the way to explain their neurotoxic effect and mode of action. Through HPLC and GC-MS analysis of the phytochemical profile ofA. houstonianumaerial parts is identified. The larvicidal activity of aerial parts; flower (AF), leaf (AL), and stem (AS) ofA. houstonianumextracts are evaluated against the 3rd instar larvae ofC. pipiensat24-, 48- and 72-post-treatment.A. houstonianiumAF, AL, and AS extracts influenced the mortality of larvae with LC50 values 259.79, 266.85, and 306.86ppm, respectively after 24h of application. The potency of AF and AL extracts was 1.69- and 1.25-folds than that of AS extract, respectively. A high repellency percentage was obtained by AF extract 89.10% at a dose of 3.60mg/cm2.A. houstonianiumAF prevailed inhibition on acetylcholinesterase and decrease in carboxylesterase activity. Moreover, a significant increase in the ATPase levels and a decrease in cytochrome P-450 monooxegenase activity (- 36.60%) are detected. HPLC analysis prevailed chlorogenic and rosmarinic acid as the major phenolic acids in AL and AF, respectively. GC-MS analysis ofA. houstonianumresults in the identification of phytol as the major makeup. Precocene I and II were detected in AF. Linoleic, linolenic, and oleic acid were detected in comparable amounts in the studied organs. Overall, results suggest that the A. houstonianum flower extract (AF) exhibits significant repellent, antifeedant, and larvicidal activities.

Pre-Clinical Characterization of a Novel Fusion Protein (AT-03), with Pan-Amyloid Binding and Removal

Background: Amyloidosis is characterized by extracellular deposition of protein fibrils that can involve any organ or tissue in the body. It is a severe, progressive and often lethal disorder. There are approximately seventeen different systemic amyloid diseases, each associated with the deposition of a specific precursor protein. Toxic amyloid deposits result in significant organ dysfunction and increased morbidity and mortality. Reduction and removal of tissue amyloid deposits could restore organ function, improve quality of life and increase life expectancy for patients. We have developed and characterized a fusion protein consisting of serum amyloid protein (SAP) linked to a single chain human IgG1 Fc domain, designated AT-03. SAP is a pentameric serum protein that is ubiquitously associated with amyloid deposits. The high affinity and specificity for amyloid resulted in the use of radio-iodinated SAP as an imaging agent for the non-invasive detection of systemic amyloid. The SAP domain of the fusion protein targets the amyloid deposits delivering Fc domains to stimulate amyloid removal via macrophage mediated phagocytosis.Methods: Binding of AT-03 to ATTR and AL fibrils and extracts was assessed by ELISA. Ex vivo phagocytosis of amyloid substrates was studied using activated human THP-1 cells. The biodistribution of AT-03 in murine models of AA, AApoA2 and AL amyloidosis was evaluated immunohistochemically or by SPECT imaging and microautoradiography. Clearance of AA amyloidosis in response to AT-03 therapy was accessed in a mouse model using histological scoring of amyloid burden.Results: AT-03 bound amyloid AL and ATTR substrates with sub nanomolar EC50 values. Systemic administration of AT-03 resulted in specific binding to diverse forms of amyloid in the heart, kidney, liver and/or spleen in multiple animal models. Opsonization of amyloid deposits with AT-03 in vitro resulted in a dose dependent phagocytosis by activated THP-1 cells. A single IV dose of AT-03 resulted in significant reduction of splenic AA amyloid within 14 days post-injection.Conclusions: We have developed a novel fusion protein with sub nanomolar pan amyloid reactivity that specifically binds diverse forms of amyloid in multiple organs and tissues in vivo and can effectuate amyloid removal. The data indicates that AT-03 may serve as a novel therapeutic for the removal of systemic amyloid deposits of diverse types. AT-03 is currently being developed for clinical evaluation. DisclosuresSirac: Attralus, Inc: Patents & Royalties, Research Funding. Jaccard: Janssen: Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria; Abbvie: Honoraria. Bridoux: AstraZeneca: Consultancy, Speakers Bureau; Janssen: Consultancy. Bell: Attralus Inc: Current Employment. Guthrie: Attralus Inc: Current Employment. Selvarajah: Attralus Inc: Current Employment. Kennel: Attralus Inc: Current holder of stock options in a privately-held company, Patents & Royalties: Inventor and patent holder. Wall: Attralus Inc: Current holder of stock options in a privately-held company, Patents & Royalties: Inventor and patent holder, Research Funding.

Treatment of Spleen-Deficiency Syndrome With Atractyloside A From Bran-Processed Atractylodes lancea by Protection of the Intestinal Mucosal Barrier.

Atractylodes lancea (Thunb.) DC. (AL) is used in traditional Chinese medicine for the treatment of spleen-deficiency syndrome (SDS). Bran-processed Atractylodes lancea (BAL) has been found to be more effective than unprocessed AL. However, the compound in BAL active against SDS remains unclear. The pharmacological efficacy of BAL and its mechanism of action against SDS were investigated by HPLC-ELSD. Candidate compound AA (atractyloside A) in AL and BAL extracts was identified by HPLC-MS analysis. AA was tested in a rat model of SDS in which body weight, gastric residual rate, and intestinal propulsion were measured, and motilin (MTL), gastrin (GAS), and c-Kit were quantified by enzyme-linked immunosorbent assay. Potential targets and associated pathways were identified based on network pharmacology analysis. mRNA expression levels were measured by qRT-PCR and protein expression levels were measured by Western blot analysis and immunohistochemistry. AA increased body weight, intestinal propulsion, MTL, GAS, and c-Kit levels, while decreasing gastric residual volume and intestinal tissue damage, as same as Epidermal Growth Factor Receptor and Proliferating Cell Nuclear Antigen levels. Seventy-one potential pharmacologic targets were identified. Analysis of protein interaction, Gene Ontology (GO) functional analysis, pathway enrichment analysis, and docking and molecular interactions highlighted MAPK signaling as the potential signal transduction pathway. Validation experiments indicated that treatment with AA increased MTL, GAS, ZO-1, and OCLN levels, while reducing AQP1, AQP3, and FGF2 levels. In addition, phosphorylation of p38 and myosin light-chain kinase (MLCK) expression were inhibited. AA improved gastrointestinal function by protecting the intestinal mucosal barrier via inhibition of the p38 MAPK pathway. The results have clinical implications for the therapy of SDS.

Artocarpus lakoocha Roxb. and Artocarpus heterophyllus Lam. Flowers: New Sources of Bioactive Compounds.

Artocarpus heterophyllus Lam. (AH) and Artocarpus lakoocha Roxb. (AL) are two endemic plants that grow on the Asian continent. To date, their applications have been aimed at using their fruit as a food source or for some of their therapeutic virtues. In this study, attention was given to the flowers of AH and AL. Initially, the cytotoxicity of the phytoextracts was assessed, and the content of minerals, phenols, and flavonoids was determined. Furthermore, some antioxidant components were identified by HPLC. Furthermore, the ability of AH and AL extracts to modulate the gene expression of some targets involved in the antioxidant response was studied. The results obtained highlighted the nutritional and antioxidant value of the AH and AL flower extracts. This study will contribute to enhancing the use of AH and AL flowers as potential supplements in human nutrition.

A new approach for green synthesis and characterization of Artemisia L. (Asteraceae) genotype extracts -Cu2+ nanocomplexes (nanoflower) and their effecitve antimicrobial activity

In this study, we have demonstrated the fabrication of novel organic-inorganic nanobio-antimicrobial agents called “nanoflowers” (NFs) and elucidate the increase in the antimicrobial activity of NFs. This is the first report that the NFs were formed of plant extracts as the organic components and copper (II) ions (Cu2+) as the inorganic component. The Artemisia L. (Asteraceae) methanol extracts from three genotypes including A. absinthium L. (Aa), A. vulgaris L. (Av) and A. ludoviciana Nutt. (Al) were selected in the NF synthesis. The effect of the plant extract concentrations on the morphology of NFs was examined. Most regular and uniform flower-shaped morphologies were observed when a concentration of 0.1 mg mL-1 plant extract was used in the synthesis of NFs. The syntesized NFs were characterized with several techniques such as scanning electron microscopy (SEM), fourier transform infrared spectrometer (FT-IR), energy-dispersive X-ray (EDX) and X-ray diffraction analysis (XRD). The NFs exhibited much antimicrobial activity against the pathogens even at low concentrations compared to the extracts. The MICs and MBCs values for NFs were found to be range between 0.4 to 40 μg mL-1 and 40 to 400 μg mL-1 while those values for Aa, Av and Al extracts were ranged from 500-2000 μg mL-1 and 1000-4000 μg mL-1 for the studied pathogens, respectively.

Comparative Study of Phytochemicals, Antioxidative Potential & Activity of Enzymatic Antioxidants of Eclipta alba and Plumbago zeylanica by in vitro Assays

Background: The Plumbago zeylanica (family: Plumbaginaceae) is a widely accepted ethnomedicine around the world including India, Pakistan, Bangladesh, Sri Lanka, and Australia. Early in vitro researches of Plumbago zeylanica were focused on antioxidant activity in root only a few were concerned with stem. Similarly in Eclipta alba antioxidant activity of whole plant is explored. Objective: The present study highlights the comparative antioxidant potential and enzymatic contents of both plants along with recent updates on phytochemical contents. Materials and Methods: The antioxidant potential of the plants was established by DPPH free radical scavenging assay, Nitric oxide (NO) free radical scavenging activity, Hydrogen peroxide (H2O2) scavenging activity, Catalase activity along with determination of Total Phenolic Contents in the plant extracts. Results: The results revealed that Eclipta alba has notable activity than Plumbago zeylanica in quenching of DPPH while Plumbago zeylanica shows comparatively better activity in nitric oxide scavenging, super oxide scavenging and Catalase activity. The Eclipta at 10 μg/ml showed maximum scavenging of DPPH (16.60 %), nitric oxide (66.21%), super oxide (4.76%) and Catalase activity 31.9 at 1 mg/g fresh weight against the Plumbago zeylanica which showed maximum scavenging of DPPH 13.24%, Polyherbal extract 11.78%, nitricoxide (69.45%), super oxide (5.12%) and catalase activity 23.7 at 1 mg/g fresh weight respectively at the same concentration. The phytochemical screening of the extract revealed the presence of considerable amount of alkaloids, saponins, tannins, phenolic compounds and glycosides which might be responsible for the antioxidative potential of the selected plants. Conclusion: The results of this study strongly indicate that the Plumbago zeylanica has comparatively more potent antioxidant potential than Eclipta alba. Moreover, the study reveals that polyherbal extract for the very first time for this combination have shown a strong antioxidant activity which is directly correlated with suppression of free radical induced diseases i.e. cancer. These findings encourage studying these plants and their polyherb al extracts further as a potential agents against cancer.

Mineralogy and chemistry of Late Pliocene–Early Pleistocene paleosols on Mount Kenya: Weathering indices of relative age and paleoenvironmental reconstruction

Iron and Al extracts as weathering indices in paleosols have been used in many localities to determine relative age, transformation of total chemical element concentrations to secondary forms, translocation of organically-complexed Al and long-standing inundation of soils with groundwater. On Mt. Kenya, a succession of paleosols straddling the Olduvai subchron are here analyzed to determine the degree to which Fe/Al extracts assist paleoenvironmental reconstruction, especially relative age determination, genesis and translocation of alteration products and the effect of paleoclimatic deterioration with the advent of glaciation ca. 2.0Ma, and possibly before. Warmer/humid climate from the onset of the Plio-Pleistocene to the Olduvai subchron, thereafter reverting to a long episode of oscillating drier/wetter ice age perturbations is written into the profile morphologies, mineralogies and chemistries supporting earlier stratigraphic interpretations.

Antioxidant and free radical scavenging activity of Pithecellobium dulce (Roxb.) Benth wood bark and leaves

Background: Several studies are going on worldwide directed towards finding natural antioxidants from plant origin which possess strong antioxidant activity. Objective: The aim of the present study was to study in vitro antioxidant and free radical scavenging activity of Pithecellobium dulce (Roxb.) Benth. Method: Methanol and 70% acetone extracts of wood bark and leaves of Pithecellobium dulce were evaluated for their total phenolic & flavonoid content, antioxidant and radical scavenging activity. Results: Total antioxidant activity (IC50 values) in DPPH assay by methanol extract of bark (MB), acetone extract of bark (AB), methanol extract of leaf (ML) and acetone extract of leaf (AL) shown 150.23 ± 2.8, 16.83 ± 0.38, 250.32 ± 4.8 and 18.30 ± 0.43 μg/ml respectively. The IC50 values for scavenging of free radicals like for hydroxyl, superoxide, nitric oxide, hydrogen peroxide, singlet oxygen and hypochlorous acid by MB, AB, ML and AL were studied. The extract was found to be a good iron chelator. The reducing power was increased with increasing amounts of extract. The MB, AB, ML & AL extracts (5 mg/ml) yielded 0.129 ± 0.11, 0.190 ± 0.14, 0.084 ± 0.24 and 0.115 ± 0.25 μg/ml gallic acid-equivalent phenolic content and 0.43 ± 0.01, 0.23 ± 0.01, 0.90 ± 0.01 and 0.25 ± 0.01 μg/ml quercetin-equivalent flavonoid content respectively. Conclusion: Thus, our findings provide evidence that the methanolic and 70% acetone extracts of P. dulce wood bark and leaves are potential source of natural antioxidants and some extent validated its medicinal potential.

IgE cross-reactivity between house dust mite allergens and Ascaris lumbricoides antigens

BackgroundCommon antigens between intestinal parasites and environmental allergens may play a role in the modulation of allergic immune responses. There is a growing interest in investigating cross-reactivity between common helminths and dust mites affecting humans, particularly in the tropics.ObjectiveThis study examined the cross-reactivity between the human roundworm Ascaris lumbricoides (Al) and three house dust mite (HDM) species.MethodsSpecific serum IgE levels to HDM species Blomia tropicalis (Bt), Dermatophagoides pteronyssinus (Dp), and Dermatophagoides farinae (Df ); and Al extracts among allergic (n=100) and ascariasis (n=60) subjects were measured through enzyme-linked immunosorbent assay (ELISA). IgE-reactive components of HDM and Al extracts were detected through Western-Blot Analysis. Cross-reactivity between HDMs and Al was determined by ELISA inhibition using HDM and Al-specific sera from allergic (n=15) and ascariasis (n=15) subjects. The IgE-binding capacity of a recombinant paramyosin peptide (Blo t 11-fD) to allergic (n=50) and ascariasis (n=50) subjects' sera were likewise determined.ResultsAmong allergic subjects, 70% exhibited Al-specific positive IgE-reactivity, while 20-28% of ascariasis subjects demonstrated HDM-specific positive IgE-reactivity. Multiple IgE-reactive components of HDM allergens (14-240 kDa) and Al antigens (15-250 kDa) were detected, indicating multi-allergen sensitization among the subjects tested. Al antigens can inhibit up to 92% of HDM-specific IgE-reactivity among allergic subjects, while up to 54% of Al-specific IgE-reactivity among ascariasis subjects was inhibited by HDM allergens. Positive rBlo t 11-fD-specific IgE reactivity was observed in 80% of the allergic subjects and 46% of the ascariasis subjects.ConclusionsThis study showed the presence of multiple cross-reactive antigens in HDM and Al extracts. Identification of these molecules may provide basis for designing novel diagnostic and therapeutic strategies. The potential role of paramyosin as a specific cross-reactive allergen present in HDMs and Al has been shown.

Quantification of Polyphenols and Pharmacological Analysis of Water and Ethanol-Based Extracts of Cultivated Agarwood Leaves

Mangiferin (3) and genkwanin 5-O-β-primeveroside (5) are the two major bioactive polyphenols with laxative property present in the extracts of agarwood (Aquilaria sinensis) leaves (AL). Here we developed an HPLC method to determine these bioactive components and four other major polyphenols in AL extracts and evaluated the pharmacological equivalence of organic and water extracts. Using mobile phase gradient conditions combined with UV detection at 330 nm, all six compounds were separated and we determined the relative extraction ratios of the six compounds present in A. sinensis extracts that were prepared under different conditions and compared the contents of the two laxative polyphenols present in the 60% ethanol extracts of A. sinensis and A. crassna. The polyphenols present in water extracts of 13 commercially cultivated A. crassna plants have also been analyzed. The laxative properties of 60% ethanol and four water extracts of A. crassna were evaluated by the frequency and weight of stools in loperamide-induced constipation model mice. The pharmacological equivalence of 60% ethanol extract and hot water (95°C) extract was identified in mice.

Rapid discrimination of three kinds of Radix Puerariae and their extracts by Fourier transform infrared spectroscopy and two-dimensional correlation infrared spectroscopy

Abstract In this study, a macroscopic IR fingerprint method, conventional Fourier transform infrared spectroscopy (FT-IR) combined with second derivative infrared spectroscopy and two-dimensional correlation infrared spectroscopy (2D-IR), was applied to quickly identify three kinds of Radix Puerariae and their ethanol extracts (AL extracts). They are authenticated as Pueraria thomsonii Benth (PTB), Pueraria lobata (Willd.) Ohwi (PLW) and simmered P. lobata (Willd.) Ohwi (PLS). By comparing the IR spectra and correlation coefficients, PTB, PLW and PLS all have comparable profiles to starch, however, PTB has relatively higher content starch comparing to PTB and PLW, and on the other hand PLW and PLS have relatively more puerarin than PTB. Though the IR spectra of PLW and PLS were almost the same, significant differences were found in 2D-IR spectra with much higher resolution. The strongest auto-peaks are at 1636 cm −1 and 1654 cm −1 in PLW and PLS, while the relative intensities are different. Moreover, the AL extracts of the three medicines were also perceivably distinguished step by step with FT-IR and 2D-IR. For example, cross-peaks at (1518, 1561) and (1518, 1568) with PLW are superior to PLS. The AL extracts had much higher correlation coefficients with puerarin than their corresponding raw materials. The contents of puerarin in the AL extracts followed the order: PLW > PLS > PTB. Therefore, it was demonstrated that the macroscopic fingerprint method of FT-IR and 2D-IR spectroscopy could be used to discriminate the three types of Radix Puerariae and their ethanol extracts rapidly and effectively.

Geochemistry and extractable Fe and Al in cold‐temperature soils of northwestern Siberia

AbstractThe concentrations of major, minor and trace elements in three Cryosols from northwestern Siberia were analysed to determine profiles of geochemical uniformity, element mobility and the release and build‐up of extractable Fe and Al. The scope of this study involves weathering processes over all or part of the Lateglacial to the Holocene Epoch (<10 ka) in a cold environment. Iron and Al extracts are investigated to elicit information regarding profile age and palaeoclimate. ‘Free’ iron (Fed) relative to total Fe increases in the Ah + Bw horizons compared with the lower horizons, where oxidation is weaker. Low total Fe reflects reworked felsic deltaic and shallow marine deposits from the Permian to the early Tertiary, thereafter emplaced by episodic flooding of glacial meltwater from the Arctic Urals and/or the Kara Sea Ice Sheet. Organically complexed Al (Alp), uniformly low in all soils, nevertheless shows trends indicating some downward movement, a rather unique occurrence in Arctic tundra soils. As indicated by the slow increase of oxihydrites, it may not be realistic to estimate the age of a profile by its physical characteristics. However, it appears possible to determine broad age ranges from the isotopic composition of water in soils. Copyright © 2009 John Wiley & Sons, Ltd.

IDENTIFICATION OF ANTIGENIC AND ALLERGENIC NATURAL RUBBER LATEX PROTEINS BY IMMUNOBLOTTING1*

ABSTRACT Quantitation of proteins in finished natural rubber latex (NRL) products is essential in predicting their allergenic potential. The ASTM standard Modified Lowry method for measuring total protein content has been used for several years. Most recently, ASTM published a standard for more sensitive and more specific enzyme immunoassay for quantitation of antigenic NRL proteins. It is an ELISA inhibition assay, using rabbit anti NRL sera. Since the measurement of proteins in this method depends on recognition capacity of rabbit antibodies, the selection of an appropriate protein source for rabbit immunization is crucial for the accuracy of such test. In this study, we evaluated the composition of NRL proteins from ammoniated (AL) and nonammoniated (NAL) raw latex and from finished NRL products, and compared the effectiveness of sera from rabbits immunized with NRL proteins, to react with those extracts. Immune rabbit sera were analyzed by immunoblotting against extracts of several samples of AL, NAL, and glove proteins. In the NAL extracts, we identified 26–28 protein bands by SDS-PAGE. AL samples had between 6 and 9 bands with a great variation in the band positions among the samples. The Western blot analysis showed that anti-AL rabbit serum reacted with 4–9 protein bands in various AL extracts. The highest intensity of reaction was observed with the extract used to immunize the rabbits. Similar reaction was observed with anti-NAL serum. However, when the antisera were blotted against NAL extracts, anti-NAL serum reacted more strongly and with a larger number of proteins than anti-AL serum. In summary, anti-NAL serum recognized an equal number of proteins in AL extract as anti-AL serum. However, anti-AL serum recognized fewer protein molecules in NAL extract than anti-NAL serum. Our findings suggest that NAL extract contains more individual proteins than other extracts, and sera from rabbits immunized with this antigen have a greater capacity to react with a wide spectrum of NRL proteins. This finding may be helpful in selecting the representative reference antigen and antiserum for further efforts in NRL protein quantitation. *The submitted manuscript has been authored by a contractor of the U.S. Government. Accordingly, the U.S. Government retains a non-exclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for Government purposes.

Determination of inorganic phosphate in a soil extract using a cobalt electrode

In soil and environmental science, a sensitive and accurate phosphate sensor would constitute a very useful tool. Several designs, mainly potentiometric and amperometric, have been published, but no commercial sensor exists. Recently, a cobalt electrode has been shown to respond to phosphate in solution. This electrode is extremely simple and robust. In this work, the cobalt electrode applicability to the measurement of phosphate in ammonium lactate-acetic acid (AL) extracts of soils was investigated. The slope of the calibration curve was -30 mV/decade; the linear part corresponded well with the concentration range usually encountered in AL extracts. Dissolved organic substances caused the electrode potential to drift and the extracts were therefore shaken with carbon black prior to measurement. Iron was shown to interfere, most likely by participating in the cathodic electrode reaction.