2-(2-Phenylethyl)Chromones And Biological Activities Of The Agarwood From Aquilaria Crassna In Laos

Agarwood,named for its sinking into water and its aroma,is a resinous core material produced by the Aquilaria plant and the Gyrinops plant of the Thymelaeaceae family by the external stress（thunder,insect,fire,etc.）.Agarwood-producing tree widely distributed in Laos,the Middle East,Cambodia,China,Myanmar,and Japan,and agarwood is very precious due to its wide application in medicine,perfume,and culture.However,wild agarwood resources are in the exhaustive risk owing to its slow formation,low yields,and high market demand.Objective:To study the chemical constituents of 2-（2-phenylethyl）chromone in the wild agarwood of Laos,and the bioactivities the isolated compounds.In order to obtain more structurally novel compounds and enrich the chemical and biological activity diversities of the compounds from agarwood of Aquilaria crassna.Methods:1.A variety of chromatographic techniques including semi-preparative HPLC(C₁₈column,C₈ column,phenyl column and naphthalene ring column,etc.),preparative thin layer chromatography,and Sephadex LH-20,etc.were used.2.Compounds were identified by various spectral methods（1D NMR,2D NMR,IR,UV,HR-ESI-MS,optical rotation,and CD calculation）and comparison with published data.3.The crude extract and the isolated compound were tested for cytotoxic and tyrosinase inhibitory activities.Results:1.Twenty-four compounds,including ten（1～10）new compounds and fourteen known compounds,were isolated from agarwood of Aquilaria crassna.Compounds 1～3 and 11～21are Fidersia type 2-（2-phenethyl）chromones;compounds 4～7,9-10,and 22～24 are 5,6,7,8-tetrahydro-2-（2-phenylethyl）chromones;compound 8 is a 2-（2-phenylethyl）chromone dimer.Compounds 1～12 and 15～24 were isolated from the agarwood of Aquilaria crassna for the first time.Compounds 9 and 10,a pair of acetyl-substituted tetrahydro 2-（2-phenylethyl） chromones,was firstly reported in the agarwood.Twenty-four compounds were identified as6-Methoxy-2-[2-（2-hydroxyphenyl）ethyl]chromone（1）,5,6-Dihydroxy-2-（2-phenylethyl）chromone（2）,6-Methoxy-2-[2-（3-hydroxyphenyl）ethyl]chromone（3）,6,7-cis-Dihydroxy-5,6,7,8-tetrahydro-2-（2-（4-methoxyphenyl）ethyl）chromone（4）,（5R,6S,7S,8R）-5,6,7-Trihydroxy-8-methoxy-5,6,7,8-tetrahydro-2-（2-（4-methoxyphenyl）ethyl）chromone（5）,rel-（5S,6R,7R,8S）-8-Chloro-5,6,7,8-tetrahydro-5,6,7-trihydroxy-2-[2-（4-methoxyphenyl） ethyl]-4H-1-benzopyran-4-one（6）,（6S,7S,8R）-6,7-Dihydroxy-8-chloro-5,6,7,8-tetrahydro-2-（3-hydroxy-4-methoxyphenyl）ethyl)chromone（7）,3′-Hydroxyaquisinenone D（8）,5β,6β,7β-Trihydroxy-8α-acetoxy-2-（2-phenylethyl）-5,6,7,8-tetrahydrochromone（9）,5β,6β,7β-Trihydroxy-8α-acetoxy-2-[2-（4-methoxyphenyl）ethyl]-5,6,7,8-tetrahydrochromone（10）.5-Methoxy-6-hydroxy-2-[2-（4’-methoxyphenyl）ethyl]chromone（11）,5-Methoxy-6-hydroxy-2-（2-phenylethyl）chromone（12）,5-Methoxy-2-[2-（3’-methoxy-4’-hydroxyphenyl）ethyl] chromone（13）,6-Methoxy-2-[2-（3’-hydroxy-4’-methoxyphenyl）ethyl]chromone（14）,6-Methoxy-7-hydroxy-2-[2-（4’-methoxyphenyl）ethyl]chromone（15）,6,7-Dimethoxy-2-[2-（3’-hydroxy-4’-methoxyphenyl）ethyl]chromone（16）,6,7-Dimethoxy-2-[2-（4’-methoxyphenyl）ethyl]chromone（17）,5-Hydroxy-2-[2-（2’-hydroxyphenyl）ethyl]chromone（18）,5-Hydroxy-2-[2-（4’-hydroxyphenyl）ethyl]chromone（19）,5-Methoxy-6-hydroxy-2-[2-（3’-hydroxy-4’-methoxyphenyl）ethyl]chromone（20）,5-Hydroxy-6-methoxy-2-[2-（3’-hydroxy-4’-methoxy phenyl）ethyl]chromone（21）,Agarotetrol（22）,5α,6β,7β,8α-Tetrahydroxy-2-[2-（4-methoxy phenyl）ethyl]-5,6,7,8-tetrahydro chromone（23）,Tetrahydrochromone F（24）.2.Cytotoxic activity was evaluated for all the isolates.The results showed that compounds 2,5,13,and 21 exhibited cytotoxicity against human chronic myeloid leukemia cells（K562）,and 2,the most potent one,showed inhibition with IC₅₀ value of 28.51±0.14（μM）;and 7 was cytotoxic to human cervical cancer cells（Hela）with IC₅₀ value of 49.82±1.20（μM）.The isolated 2-（2-phenethyl）chromones were also tested for the tyrosinase inhibitory activity.Compounds 2,13,15,16,and 17 exhibited tyrosinase inhibitory activity（The inhibition rate is between 20%and 55%at 100μM）.The most effective compound,2showed inhibition with IC₅₀ value of 172.6±1.7μM（Positive control:kojic acid,46.1±1.3μM）.Conclusion:This study continued the phytochemical investigation on the agarwood of Aquilaria crassna,which enriched the chemical and bioactivity diversities of constituents of agarwood from Aquilaria crassna,and provided the scientific basis for the development and utilization as well as quality evaluation of agarwood from Aquilaria crassna.