Ecological origin of the appearance of sesquiterpenes in Gyrinops walla Gaetner by wood anatomical and chemical analysis

摘要

Abstract Agarwood oil obtained from a number of genera of the family Thymelaeaceae is an expensive product in the global market. Gyrinops walla produces fragrant resinous substance similar to agarwood produced by Aquilaria spp. and Gonystylus spp. in mature and damaged stems and branches when they become infected with a particular type of mould. The present study focused on anatomical characteristics in healthy and infected wood of G. walla, and distribution of agarwood-type constituents based on their ecological habitats. Anatomical features of transverse, tangential and radial sections of healthy and infected wood samples were stained with safranin and observed under light microscope. The characteristics of wood colour, growth rings, vessel elements, ray parenchyma, axial parenchyma, intercellular spaces, tyloses and mineral inclusions and the distribution of phloem in wood sections were observed and described. White wood sections of G. walla were dried and grounded to execute solvent extraction. Thin-layer chromatography (TLC) and gas chromatography–mass spectroscopy (GC–MS) were performed to identify agarwood-type constituents in each geolocation. Wood anatomy of healthy and infected G. walla wood samples indicated similar anatomical features. Accumulated brownish substances in ray parenchyma, included phloem and xylem vessels in the wood signify the functional importance in agarwood production, and depositions in infected wood imply the involvement of living cells of the wood in the formation of agarwood and xylem as a storing tissue. Due to the appearance of higher amounts of sesquiterpenes on GC–MS analysis of wood extracts of samples collected from Gampaha District, Sri Lanka differs from the rest of the districts indicating an ecological provenance of agarwood formation in G. walla.