Four new bi-phenylethylchromones from artificial agarwood

Agarwood is the fragrant resinous heartwood harvested from the Aquilaria species of the family Thymelaeaceae, which was mostly distributed in China, Japan, India and Southeast Asian countries [1], [2] and was widely used in incenses, perfumes, traditional medicines and other products in the world market [3]. Aquilaria sinensis (Lour.) is the main plant resource of Chinese agarwood, and the wild agarwood was close to exhausted due to the condition particularity of formation and a long period of time required for agar to accumulate in the wound tissues of trees [4], [5], coupled with the increase of commercial demand resulted in the anthropogenic deforestation. Fortunately, the holing method has widely been accepted recently to produce artificial agarwood attributed to the good quality of the product and the lasting aroma of its ether extract [5], [6]. Despite the commercial and biological significance of artificial agarwood, only a few researches on chemical constituents was conducted, which led to a series of sesquiterpenoids and 2-(2-phenylethyl)chromones [7], [8], [9], [10], [11].

Though 2-(2-phenylethyl)chromones were widely distributed in agarwood, and was considered as one of diagnostic components of agarwood quality [8], [9], [12], [13], the research progress about phenylethylchromone polymers (including dimer and trimer) was slow that no more than eleven analogues have been reported since the first one was isolated from the Kalimantan agalwood named “Jinko” and characterized by Iwagoe et al. in 1986 [14], [15], [16], [17], [18].

With the aim to study the chemical constituent of artificial agarwood, as well as to expand the diversity of bioactivities and chemical structures of bi-phenylethylchromones, the ongoing chemical investigation on agarwood induced by artificial holing was carried out, which led to the isolation and identification of four new bi-phenylethylchromone derivatives (1–4). Their structures were elucidated by extensive UV, IR, 1D and 2D NMR, and the absolute configuration was determined by electronic circular dichroism (ECD) spectroscopic analysis. All compounds were tested for AChE and α-glucosidase inhibitory activity.