Chemical Profiles of Cultivated Agarwood Induced by Different Techniques

Abstract

Agarwood is the resinous wood produced in some Aquilaria species and is highly valued for wide usages in medicine, incense, and perfume. To protect the threatened Aquilaria species, the cultivation of Aquilaria sinensis and artificial agarwood induction techniques have been effectively established in China. To evaluate the quality of agarwood induced by different techniques, patterns of chemical constituents in artificial agarwood by four methods (wounding using an axe, burning-chisel-drilling, chemical inducer, and biological inoculation) were analyzed and compared by UPLC-ESI-MS/MS and GC-EI-MS in this study. Results of GC-MS gave a panorama of chemical constituents in agarwood, including aromatic compounds, steroids, fatty acids, sesquiterpenoids, and 2-(2-phenlyethyl)-chromones (PECs). Sesquiterpenoids were dominant in agarwood induced by wounding using an axe. PEC comprised over 60% of components in agarwood produced by biological inoculation and chemical inducers. PECs were identified by UPLC-ESI-MS/MS in all artificial agarwood and the relative contents varied in different groups. Tetrahydro-2-(2-phenylethyl)-chromones (THPECs) in wounding by axes induced agarwood were lower while 2-(2-phenylethyl)-chromones (FPECs) were higher than other groups. The results showed that methods used for inducing agarwood formation in Aquilaria sinensis affect the chemical constituents of agarwood.

Effects of various artificial agarwood-induction techniques on the metabolome of Aquilaria sinensis

“…In spite of the fact that agarwood-producing plants such as A. sinensis take a long time to develop and the agarwood-formation process takes an equivalent amount of time, the demand for agarwood and its derivatives is on the rise [ 4 , 13 , 28 ]. To overcome this, A. sinensis is intentionally wounded to produce agarwood [ 11 , 13 , 37 – 39 , 44 ]. The quantity and quality of agarwood is well documented to be influenced by locations and induction techniques [ 13 , 45 – 47 ].…”

“…Traditional agarwood induction methods and non-traditional agarwood induction methods are the two most common types of agarwood induction methods available. Physical incursions such as burning, chisel drilling, and wounding with an axe are used in the traditional procedures, which have been in use in China for about 1000 years [ 13 ]. Other non-traditional induction strategies include trunk injection with solvents that contain ions or microbial additives to facilitate the production of agarwood [ 4 , 11 , 14 ] and trunk injection with solvents that contain ions but do not contain any microbial additives [ 4 , 11 , 14 ].…”

“…Traditional induction techniques are being investigated for the manufacture of agarwood, however such research is still in its early phases [ 4 , 11 ]. Since there are different methods of agarwood production, a comparison of chemical constituents is absolutely required to gain comprehensive knowledge on quality and metabolite profiles of agarwood [ 8 , 13 ]. Further studies are required to elucidate the mechanism of secondary metabolites accumulation in agarwood induced by non-traditional techniques.…”

“…Chromone profiling using liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) separated chromones into three groups: tetrahydro-2-(2-phenylethyl) chromones (THPECs), epoxy-(2-phenylethyl) chromones (EPECs), and diepoxy-(2-phenylethyl) chromones (DEPEC). A large number of studies have indicated that both chromones and sesquiterpenes are essential for the medicinal and incense applications of agarwood [ 4 , 8 , 13 ]. Recently, it has been revealed that the quantity of chromones in agarwood fluctuates throughout agarwood production [ 25 ], but 2-(2-phenylethyl) chromones have been shown to accumulate significantly in high-quality agarwood [ 8 , 13 , 23 , 25 ].…”

“…A large number of studies have indicated that both chromones and sesquiterpenes are essential for the medicinal and incense applications of agarwood [ 4 , 8 , 13 ]. Recently, it has been revealed that the quantity of chromones in agarwood fluctuates throughout agarwood production [ 25 ], but 2-(2-phenylethyl) chromones have been shown to accumulate significantly in high-quality agarwood [ 8 , 13 , 23 , 25 ].…”