Determination of the purple pigment in the heartwood ofDalbergia congestiflora Pittier B.E.Barraga Ân,L.Herna Ândez, J. Peralta The present text describes a method for the isolation by solid phase extraction of the purple pigment present in D. congesti¯ora heartwood. It also presents the procedure applied to obtain maximum pigment extraction. Purple pigment quanti®cation was carried out by densitometry, showing that its concentration in the heartwood of D. congesti¯ora amounted to approximately 4.85% of dry matter. Bestimmung des Purpur-Farbstoffs im Kernholz von Dalbergia congestiflora Pittier Es wird eine Methode beschrieben, den Purpur-Farbstoff im Kernholz von Dalbergia congesti¯ora in maximaler Ausbeute zu gewinnen. Die Isolierung erfolgte mittels ei- ner Festphasenextraktion auf einer Si-2OH Sa Èule.Die densitrometrische Bestimmung wurde mittels HPTLC auf Kieselgel-beschichteten Platten durchgefu Èhrt.Die Ergeb- nisse zeigten, daû der reine Farbstoff in einer Konzentra- tion von 4,85%. im Kernholz vorliegt. 1 Introduction The wood from trees of Dalbergia genus is intensively used in Me Âxico for handcrafts products, furniture and for the elaboration of musical instruments (Guridi-Go Âmez and LoÂpez 1996) due to its hardness, resonance and color, the latter varying according to species. The ®rst published data on the presence of purple pigments in the wood of Dalbergia genus were presented by Hamburger et al. (1988). They reported that heartwood extracts from a Thailand species (D. candenatensis) contained a complex mixture of yellow and purple pigments, all of them in smallamounts. After a complex method of puri®cation, they obtained a purple pigment in low performance and determined its structure. Our team recently reported on pigment occurrence in high percentage in the wood of a Mexican species: Dalbergia congesti¯ora. These previous studies were focused on characterizing the coloured ex- tract for technological application (Barraga Ân et al.1995). In the present paper, the results of a laboratory level study are presented. The aim was to obtain maximum pigment performance in minimum time and solvent cost, as well as its puri®cation by solid phase extraction and the quantitative determination in alcohol extracts by high performance densitometry on silica plates (HPTLC). 2 Methods The wood was collected and identi®ed in the Mexican state of Michoaca Ân and milled to sawdust. A pilot cyclic ex- traction was made with ethanol using a high wood/solvent rate (1:50) for a period of three hours, in order to determine the maximum recoverable quantity of alcoholic extract. To optimize the process, a series of batch extractions was developed, using the minimum ethanol quantity to cover the wood (wood/ethanol rate 1:5). Extraction was followed by spectrophotometry at 550 nm every 15 min. After 60 min, heating was suspended and the sample was ®ltered. The ®ltrate was evaporated, dried and the weight registered. Recovered ethanol was reused for a renewed extraction of the previously obtained residue, always keeping the 1:5 rate. The process is schematically de- scribed in Fig. 1. An alcoholic extract sample thus obtained was puri®ed by solid phase extraction (Van Horne 1990) using silica gel column modi®ed with diol groups (Varian Si2-OH 500 mg/3 ml). Puri®cation was followed by thin layer chromatography on silica gel, using a solvent system of ethylacetate/ethanol/NH 3 , 4:1:0.25 and developing with 254 nm UV light. The pigment thus obtained was used as standard for further densitometry quanti®cation. To this end, plates of Merck's High Performance Thin Layer Chromatography (HPTLC) were employed and measured in a Desaga CD-60 densitometer with an AS-30 sample applicator and a Spark Holland BV auto-sampler, model 816. 3 Results The maximum portion of alcoholic extract that can be obtained was determined to amount 24.25% in relation to dry wood. Holz als Roh- und Werkstoff 57 (1999) 347±349 Ó Springer-Verlag 1999 Originalarbeiten á Originals B.E.Barraga Ân,J. Peralta Department of Organic Chemistry National School of Biological Sciences I.P.N. Prof.Carpio y Plan de Ayala s/n CP. 11340, MeÂxico DF L. Herna Ândez Department of Pharmacy National School of Biological Sciences I.P.N. Prof.Carpio y Plan de Ayala s/n CP. 11340, MeÂxico DF Correspondence to: B.E.Barraga Ân Thanks to engineer Jose ÂRutiaga Quin Äones for wood conditioning, to biologist Lydia Guridi Go Âmez for wood identi®cation. To Merck-Me Âxico Co.for the given permission of access to the densitometer. 347