Hui Meng

Whole-tree Agarwood-Inducing Technique: An Efficient Novel Technique for Producing High-Quality Agarwood in Cultivated Aquilaria sinensis Trees

Agarwood is the fragrant resin-infused wood derived from the wounded trees of Aquilaria species. It is a valuable non-timber forest product used in fragrances and as medicine. Reforestation for Aquilaria trees in combination with artificial agarwood-inducing methods serves as a way to supply agarwood and conserve of wild Aquilaria stock. However, the existing agarwood-inducing methods produce poor-quality agarwood at low yield. Our study evaluated a novel technique for producing agarwood in cultivated Aquilaria trees, called the whole-tree agarwood-inducing technique (Agar-Wit). Ten different agarwood inducers were used for comparison of Agar-Wit with three existing agarwood-inducing methods. For Aquilaria trees treated with these ten inducers, agarwood formed and spread throughout the entire tree from the transfusion point in the trunk to the roots and branches of the whole tree. Agarwood yield per tree reached 2,444.83 to 5,860.74 g, which is 4 to 28 times higher than that by the existing agarwood-inducing methods. Furthermore, this agarwood derived from Agar-Wit induction was found to have a higher quality compared with the existing methods, and similar to that of wild agarwood. This indicates Agar-Wit may have commercial potential. Induction of cultivated agarwood using this method could satisfy the significant demand for agarwood, while conserving and protecting the remaining wild Aquilaria trees.

Hydrogen peroxide induces vessel occlusions and stimulates sesquiterpenes accumulation in stems of Aquilaria sinensis

Agarwood is highly valuable resinous and fragrant heartwood, produced principally from tropical tree species in the genus Aquilaria, which is used widely in countries of the Middle East, Southeast Asia and Japan. Generally, healthy trees will not produce agarwood, but wounding of the tree initiates the production of agarwood. In this study, the pruning of actively growing saplings of Aquilaria sinensis resulted in hydrogen peroxide (H2O2) burst, which was followed by formation of vessel occlusions and sesquiterpene biosynthesis in the pruned stems. Treatment of the pruned stems with scavenger of H2O2 (ascorbate, AsA) greatly reduced the amount of H2O2 released, the number of vessel occlusions, and the amount of sesquiterpenes produced. In addition, exogenous H2O2 also induced A. sinensis plants to form vessel occlusions and produce sesquiterpenes as pruning treatment. The results indicated that H2O2 may be an important post-wounding signal in A. sinensis that leads to the induction of vessel occlusions formation and sesquiterpene biosynthesis, and thus H2O2 might play a vital role in agarwood formation in pruned stems of A. sinensis.

The Sesquiterpene Biosynthesis and Vessel-Occlusion Formation in Stems of Aquilaria sinensis (Lour.) Gilg Trees Induced by Wounding Treatments without Variation of Microbial Communities

As widely recognized, agarwood formation in Aquilaria trees is induced by external wounding. Because agarwood usually harbors specific microbes, the function of microbes in agarwood formation has been debated for almost a century. In this study, two wounding methods, the burning-chisel-drilling method (BCD) and the whole-tree agarwood-inducing method (Agar-Wit), were used under the non-contamination of environmental microorganisms. After pyrosequencing the small rRNA subunits of the wounds induced by the BCD and Agar-Wit, no substantial variation was observed either in fungal and bacterial enrichment and diversity or in the relative abundances of taxa. By contrast, significant variations in fungal and bacterial communities were detected following the partial tree pruning (PTP)-wounding. The wound-induced sesquiterpene biosynthesis and vessel-occlusion formation, however, were found to be similar in all types of wounded trunks. We thus infer that wounding in the absence of variations in microbial communities may induce agarwood formation. This result does not support the long-standing notion that agarwood formation depends on microbes.

Sesquiterpenoids with cytotoxicity from heartwood of Dalbergia odorifera

Abstract Two new sesquiterpenoids, named dalodorin A (1) and dalodorin B (2), together with four known sesquiterpenoids, were isolated from the heartwood of Dalbergia odorifera. Their structures were elucidated on the basis of spectroscopic analysis including 1D and 2D NMR techniques and HR-ESI-MS. Evaluation of the isolated compounds for cytotoxicity against two human cancer cell lines (Hela and HepG-2) showed moderate activities (25.22–60.45 μM).