Natural products in agarwood andAquilariaplants: chemistry, biological activities and biosynthesis

Abstract

This review provides a comprehensive summary of the research progress on natural products from agarwood and Aquilaria trees, including chemistry, biological activities and biosynthesis.

The Characteristic Fragrant Sesquiterpenes and 2-(2-Phenylethyl)chromones in Wild and Cultivated “Qi-Nan” Agarwood

“…As presented in Figure 3 A, both of WQN and CQN showed high contents of 2-(2-phenylethyl)chromones. Especially, the relative content of the two main 2-(2-phenylethyl)chromones, 2-(2-phenylethyl)chromone ( 59 ) and 2-[2-(4-methoxyphenyl)ethyl]chromone ( 60 ), was very high (43.89–73.04% in WQN agarwood and 72.43–95.61% in CQN agarwood in this study), which was consistent with the result of our previous study [ 7 , 23 ] and Ishihara’s discovery [ 27 ]. Most of the CQN agarwood possessed higher contents of ( 59 ) and ( 60 ) than the levels found in WQN agarwood.…”

“…Both of the two aforementioned agarwood varieties were reported as “Qi-Nan” agarwood and were richer in guaiane sesquiterpenes compared with CQN, while the structural characteristics of guaiane sesquiterpenes in the two agarwood types were totally different, which may be due to their different origin plants. At present, 15 agarofuran sesquiterpenes have been reported from agarwood [ 23 ]. Only three ( 10 , 11 and 12 ) of them were isolated from the two above noted high-quality “Qi-Nan” agarwood varieties and others were identified from ordinary agarwood [ 23 ].…”

“…At present, 15 agarofuran sesquiterpenes have been reported from agarwood [ 23 ]. Only three ( 10 , 11 and 12 ) of them were isolated from the two above noted high-quality “Qi-Nan” agarwood varieties and others were identified from ordinary agarwood [ 23 ]. Although significant differences in the relative contents of agarofuran sesquiterpenes between WQN and CQN agarwood were observed in this study, it is hard to say that agarfuran sesquiterpenes could be a chemical marker for high quality agarwood.…”

“…Sesquiterpenes and 2-(2-phenylethyl)chromones were reported as their main constituents. Guaianes, eudesmanes, and eremophilanes are the three main types of sesquiterpenes found in the two wild “Qi-Nan” agarwood varieties, together with several agarofurans, agarospiranes, acoranes, cadinanes ( Figure 1 ) [ 22 , 23 ]. In particular, guaianes show great structural diversity and might be used as markers for different kinds of agarwood.…”

“…As for 2-(2-phenylethyl)chromones, 23 of them, except for 6-methoxy-2-[2-(4-methoxyphenyl)ethyl]chromone ( 67 ), have been isolated from the Chinese agarwood “Lv Qi-Nan” of A. sinensis , while only three—2-(2-phenylethyl)chromone ( 59 ), 2-[2-(4-methoxyphenyl)ethyl]chromone ( 60 ), and ( 67 )—have been isolated from kanankoh; a high-quality agarwood of A. agallocha ( Figure 2 ). Compounds ( 59 ) and ( 60 ) are two typical 2-(2-phenylethyl)chromones without substitution of the chromone moiety, which are most abundant in high quality “Qi-Nan” agarwood, as well as frequently found in most ordinary agarwood with a low relative content [ 22 , 23 ]. A 2-(2-phenethyl)chromone glycoside ( 72 ) was obtained from the high-quality “Lv Qi-Nan” of A. sinensis , which is the only chromone glycoside reported from agarwood up to now [ 17 ].…”