Quality and characteristic chemical composition of Chinese agarwood ‘Qi-Nan’ induced by drilling

Objective  This study aims to determine the optimal spacing for drilling-induced agarwood formation in Qi-Nan agarwood and to explore the quality of the resulting agarwood, providing guidance for future applications and production.

Methods Different drilling distances of 4 cm (FW), 8 cm (EW), and 16 cm (SW) were used to induce agarwood formation over 12 months. The contents of alcoholic extracts and essential oils were analyzed, along with chromatic reactions. Volatile sesquiterpenes and 2-(2-phenylethyl) chromones (PECs) were characterized using gas chromatography-mass spectrometry (GC-MS), and non-volatile PECs were further analyzed by high performance liquid chromatography-mass spectrometry (HPLC-MS).

Results (1) The content of alcoholic extracts for FW, EW, and SW treatments was (42.01 ± 1.86)%, (46.60 ± 0.73)%, and (42.54 ± 2.15)%, respectively, with essential oil contents of (37.47 ± 1.45)%, (40.47 ± 0.91)%, and (37.33 ± 1.14)%. (2) Chromatic reactions of the Qi-Nan agarwood samples appeared purple, cherry red, and reddish-purple, all conforming to the standards of Pharmacopoeia of the People’s Republic of China. (3) A total of 40 volatile compounds were identified, with the combined sesquiterpenes and PECs under FW, EW, and SW treatments amounting to 36, 38, and 38, and relative contents of 86.63%, 91.89%, and 79.10%, respectively. (4) A total of 62 non-volatile PECs were identified, including 5 2,2′-Diepoxy-2-(2-phenylethyl)chromone (DEPECs), 6 Monoepoxy-2-(2-phenylethyl)chromone (EPECs), 3 Tetrahydro-2-(2-phenylethyl)chromone (THPECs), and 48 Flidersia-type 2-(2-phenylethyl) chromone (FTPECs), with detailed analysis of the cleavage patterns for these chromone types. Metabolomics analysis successfully distinguished samples under different drilling distances (SW and EW-FW).

Conclusion Drilling treatment demonstrated high efficacy in inducing agarwood formation in Qi-Nan agarwood, with EW treatment being particularly effective. This innovative method not only significantly enhances resin formation efficiency but also drastically reduces the required time, thereby improving both the yield and quality of agarwood, offering promising applications.