Remarkable Phytochemical Characteristics of Chi-Nan Agarwood Induced from New-Found Chi-Nan Germplasm of Aquilaria sinensis Compared with Ordinary Agarwood

Abstract

Wild Chi-Nan agarwood is regarded as the highest quality agarwood from Aquilaria spp. However, the comprehensive research on chemical composition of wild Chi-Nan agarwood is limited. An integrated strategy using SHS-GC-MS and UPLC-Q/Tof-MS was applied to explore the phytochemical characteristics of a kind of agarwood induced from a newly identified germplasm of Chi-Nan A. sinensis. Progenesis QI and MS-Dial were used to preprocess the UPLC-Q/Tof-MS and GC-MS raw data, respectively. Principle component analysis (PCA) and orthogonal partial least squares to latent structure-discriminant analysis (OPLS-DA) models were built to discriminate Chi-Nan agarwood from ordinary agarwood and to screen potential distinguishing components between them. In this study, we clarified the distinguishing differences between Chi-Nan agarwood and ordinary agarwood. The difference is mainly manifested in the average contents of 2-(2-phenylethyl)chromone and 2-[2-(4'-methoxybenzene)ethyl]chromone, which are 170 and 420 times higher in Chi-Nan agarwood than in ordinary agarwood, respectively, while the contents of 5,6,7,8-diepoxy-2-(2-phenylethyl)chromones(DEPECs), 5,6-epoxy-2-(2-phenylethyl)chromones(EPECs), and 5,6,7,8-tetrahydro-2-(2-phenylethyl)chromones(THPECs) such as agarotetrol are extremely low. The content of the main sesquiterpenes in Chi-Nan agarwood was higher than that in ordinary agarwood, especially in regard to guaiane and eudesmane derivatives. In addition, there were significant differences in the contents of low-molecular-weight aromatic compounds such as 2-methyl-4H-1-benzopyran-4-one, 4-methoxybenzaldehyde, and 2-hydroxybenzaldehyde between Chi-Nan agarwood and ordinary agarwood. All the mentioned main chemical characteristics of this new Chi-Nan agarwood were coincident with those of the rare wild Chi-Nan agarwood from A. malaccensis, A. sinensis, and A. crassna. We reported differences in 2-(2-phenylethyl)chromones, sesquiterpenes, and low-molecular-weight aromatic compounds between Chi-Nan agarwood and ordinary agarwood from A. sinensis for the first time; it is necessary to evaluate the agarwood from the new-found Chi-Nan germplasm.

Figure 1

The total ion chromatograms of Chi-Nan agarwood (CNA1) and ordinary agarwood (OA1) acquired by LC-MS. (a zone: 0–10 min; b zone: 10–15 min; c zone: 15–30 min).

Figure 2

PCA (a) and OPLS-DA (b) scores plots for the first two components of Chi-Nan agarwood (filled triangle)and ordinary agarwood (filled square) data analyzed by LC-Q/Tof-MS.

Figure 3

The total ion chromatograms of typical agarwood samples (OA1 and CNA1) acquired by SHS-GC-MS and the corresponding temperature gradientvariety diagram (a zone: 0–10.6 min; b zone: 10.6–34.0 min; c zone: 34.0–45 min).

Figure 4

PCA (a) and OPLS-DA (b) scores plot for the first two components of Chi-Nan agarwood (filled triangle) and ordinary agarwood (filled square) data analyzed by GC-MS.

Figure 5

Comparison of sesquiterpenes in different configurations between the CNA (colored blue) and OA (colored yellow) (the stars on the boxes represent mean values of different types of sesquiterpenes). The stars on the boxes represent mean values. The median is drawn as a black horizontal line inside the box.

Figure 6

S-plot at the first component used in potential distinguished components selection based on LC-Q/Tof-MS (a) and GC-MS (b), constituent ions with VIP value >4 were marked with a black square, compounds marked with yellow stars are richer in CNA, and dark blue marked compounds are richer in OA.