Metabolites change reveal insights into the heartwood color formation mechanism of Dalbergia odorifera

Dalbergia odorifera T. Chen, an indigenous species in Hainan Island, China, had high economic and cultural values. Its sapwood was light yellow, while, heartwood was rich in colors of red, yellow, orange and black. The colorful oily deposits were found in the vessels, fibers and parenchyma cells of the heartwood. The contents of extractives, flavonoid and anthocyanin in heartwood were found to be 11.83%, 34.88 mg/g and 705.84 μg/g, 3.29 times, 12.37 times and 9.51 times higher than that of sapwood, respectively. More extractives, flavonoid, anthocyanin appeared in the transition zone in heartwood area position with abundant metabolites. Among them, flavonoids were 26.2%. The relative content of metabolites such as anthocyanins, chalcone, flavone and anthraquinone increased greatly in heartwood. The formation of red-yellow-orange mixed color of Dalbergia odorifera heartwood was related to these metabolites.