Molecular Size Distribution of Radiata Pine Bark Extracts and its Effect on Properties

Abstract

Various aqueous extracts from Pinus radiata and Acacia mearnsii barks were fractionated by ultrafiltration on the basis of molecular size* All the monomeric, dimeric and oligomeric compounds were concentrated in the fraction containing compounds with molecular sizes sinailer than a io 3 molecular weight Dextran. High yields of hot-water-soluble material have been obtained from the radiata pine bark and shown to have promise äs a base for adhesives. However, the excessive viscosity of the untreated extracts limits their commercial use. The particularly high viscosity of the ioo°C aqueous extracts of P. radiata bark was reduced markedly by removing either the methanol insolubles or the high polymeric material with a molecular size larger than io e molecular weight Dextran by ultrafiltration. Both the methanol insolubles and the high polymeric material are viscosity control factors. In addition, examination of various extracts and fractions revealed that the molecular size distribution of the extracts is a viscosity control factor. Chromatographie examination of sulphited ioo°C aqueous pine bark extracts revealed a compound with behaviour exactly the same äs the major product from a reaction of catechin with sodium bisulphite. The compound was isolated and identified äs i-sodium sulphonate-(3,4-dihydroxyphenyl)-2-hydroxy-3-(i ,3,5-trihydroxyphenyl) propane. The amounts of Stiasny precipitate produced by various extracts, fractions or the sulphited extracts were determined and found to be lowest in the fraction with molecular sizes smaller than io 3 molecular weight Dextran. Purification of the extracts by ultrafiltration produced extracts having low viscosities and yielding suitable amounts of Stiasny precipitate which indicate high and uniform qualities of extract. Molekulargewichtsverteilung in Rindenextrakten von Radiata Kiefer und ihr Einfluß auf die Eigenschaften ZusammenfassungVerschiedene Rindenextrakte von Pinus radiata und Acacia mearnsii wurden durch Ultrafiltration nach der Molekulargröße fraktioniert. Alle monomeren, dimeren und oligomeren Verbindungen jeder Fraktion wurden konzentriert, wobei die Molekulargewichte kleiner als io 3 , bezogen auf Dextran, waren. Hohe Ausbeuten an heißwasserlöslichen Stoffen ergaben sich bei Radiata Kiefernrinden, die möglicherweise als Grundlage für Bindemittel dienen können; ihre hohe Viskosität begrenzt jedoch ihre wirtschaftliche Anwendung. Die besonders hohe Viskosität der ioo°C Extrakte aus Radiata Kiefernrinde kann beträchtlich vermindert werden entweder durch Entfernen der methanolunlöslichen Stoffe oder durch Entfernen der hochpolymeren Anteile von einem Molekulargewicht über io 6 mittels Ultrafiltration. Die beiden genannten Bestandteile bestimmen die Viskosität. Ferner zeigt die Prüfung der verschiedenen Extrakte und Fraktionen, daß die Molekulargewichtsverteilung in den Extrakten für die Viskosität bestimmend ist. Aus chromatographischen Untersuchungen an sulfitierten ioo°C Rindenextrakten geht hervor, daß hier eine Verbindung mit genau demselben Verhalten vorl...

Characterization of Pinus pinaster bark and its alkaline extracts by diffuse reflectance Fourier transform infrared (DRIFT) spectroscopy

“…The Stiasny number of the extracts, a measure of their purity, was determined according to the procedure proposed by Yazaki and Hillis (1980).…”

Characteristics of Pinus pinaster bark extracts obtained under various extraction conditions

“…Stiasny numbers, which re¯ect formaldehyde-condensable polyphenol content, were determined as per Yazaki and Hillis (1980). The gel time of a 7.5:100 (w/w) paraformaldehyde/extract mixture was determined as a measure of extract reactivity: an aqueous solution of extracts with a 20% solids content was mixed with the appropriate weight of paraformaldehyde, and the time required for the resulting mixture to gel in a water bath at its boiling point (98°C) was determined as per Pizzi and Stephanou (1994).…”

“…Like the extracts of other barks (Weissman 1983, SuomiLindberg 1985, Yazaki and Collins 1994aand b, Grigoriou 1997, those of Pinus pinaster thus have quite high viscosities at the solids contents commonly used in adhesive formulations. However, this does not necessarily rule out their utility, since a) satisfactory results have been obtained with tannin-based adhesives with relatively low solids contents (Pizzi and Stephanou 1994), and b) the viscosity of the extracts can be reduced by sulphitation (Yazaki and Hillis 1980, Weissmann 1983, Yazaki and Collins 1994a or the addition of hydrogen bond breakers (Ayla andWeissmann 1981, Grigoriou 1997). due to both chemical composition and susceptibility to grinding varying from one region of the bark to another.…”

Optimisation of Polyphenols Extraction from Chestnut Shell by Response Surface Methodology

“…The Stiasny number of the extracts was determined according to the procedure proposed by Yazaki and Hillis [17]. The extract (0.25 mg) was dissolved in distilled water (100 mL) and 2.5 mL of 10 M HCl (Panreac, Barcelona, Spain) and 5 mL of 37% formaldehyde (Panreac, Barcelona, Spain) were added.…”