Studies On The Chemical Constituents And Their Neuroprotective Activity Of The Heartwoods Of Aquilaria Sinensis Produced In Guangdong

Chinese agarwood,the resinous heartwoods of Aquilaria sinensis(Lour.)Spreng.(Thymelaeaceae),is a precious traditional Chinese medicine and natural flavor.It has functions of xing-qi zhi-tong,wen-zhong zhi-ou,and na-qi ping-chuan and used to treat thoraco-abdominal distension and pains(xiong-fu zhang-men teng-tong),stomach cold vomiting and hiccup(wei-han ou-tu e-ni),and asthma due to the kidney deficiency(shen-xu qi-ni chuan-ji).In our previous research,it was found that agarotetrol,a major constituent of chinese agarwood,promotes PC12 neuron-like cell differentiation.In the present study,chemical constituents from the heartwoods of A.sinensis will be isolated and screened for neuroprotective activities to find active compounds.Based on organic solvent extraction,macroporous adsorption resin,silica gel and gel column chromatography,and high performance liquid chromatography(HPLC),combined with mass spectrometry(MS),ultraviolet spectroscopy(UV),infrared spectroscopy(IR),nuclear magnetic resonance(NMR),single crystal X-ray diffraction,electronic circular dichroism(ECD)calculations,29 compounds(1–29)were isolated and identified from the EtOAc-soluble part of chinese agarwood.Compounds 1–6 are new isolates,including three sesquiterpenoids,(4S,5S,7S,8S,11R)-7-hydroxyguai-1(10)-en-8,12-olide(1),aquilarisinone(2),and 2Z,7(13),9E-humulatrien-12-ol-5-one(3),one diphenylpentanone,1-(2-hydroxyphenyl)-5-phenylpentan-3-one(4),and two 2-(2-phenyl)chromones,6-epiagarotetrol(5)and oxidoagarochromone D(6).Twenty-three known compounds(7–29)include 12 sesquiterpenoids,(4S,7S,8S,10R,11R)-7,10-epoxyguai-1(5)-en-8,12-olide(7),selina-4,11-diene-12,15-dial(8),(+)-(7R,10R)-methyl 15-oxoeudesma-4,11(13)-dien-12-oate(9),(-)-(5R,7R,10R)-11-hydroxyeudesm-3-en-15-al(10),(-)-(5R,7R,10R)-12,15-dioxo-α-selinen(11),(+)-(7S,9S,10S)-9β-hydroxyeudesma-4,11-dien-3-one(12),(+)-(1R,4S,5R)-1β-hydroxyeremophila-7(11),9-dien-8-one(13),(-)-(4S,5R,7R)-11,12-epoxyeremophil-9-en-8-one(14),neopetasan(15),(+)-(4S,5R,7R,10S)-10β-hydroxyeremophil-11(13)-en-12-al(16),(+)-daphnauranol B(17),(-)-auranticanol A(18)and(-)-chamaejasmone(19),one diphenylpentanone,1-hydroxy-1,5-diphenylpentan-3-one(20),seven 2-(2-phenyl)chromones,5-hydroxy-6-methoxy-2-(2-phenylethyl)chromone(21),2-(2-phenylethyl)chromone(22),6-methoxy-2-(2-phenylethyl)chromone(23),6-methoxy-2-[2-(3-methyoxyphenyl)ethyl]chromone(24),5-hydroxy-2-(2-phenylethyl)chromone(25),isoagarotetrol(26),and agarotetrol(27),one phenylpropanoid,coniferaldehyde(28),and one steroid,stigmasterol(29).Among them,compound 12 is a new natural product.Compounds 9,10,and 13 were isolated from Aquilaria for the first time,and compounds 17,18,19,and 20 were isolated from chinese agarwood for the first time.The isolated compounds from chinese agarwood were evaluated for inhibitory activity againstβsecretase(BACE1).The results showed that several compounds had very weak inhibitory activity onβ-secretase(BACE1),and coniferaldehyde(28)possessed the best activity.At a concentration of 20μM,the inhibition rate on BACE1 was 17.2%.The protective effect of corticosterone-induced neuronal damage was evaluated on the compound isolated from chinese agarwood.At a concentration of 2μM,compound 6,8,and 11 has a very significant protective effect on PC12 cell injure induced by corticosterone(P<0.001),while compounds(16)have a significant protective effect(P<0.05).At a concentration of 20μM,compound(13)has a very significant protective effect on PC12 cell injure induced by corticosterone(P<0.001),while compounds 1,7,9,and 18 have a significant protective effect(P<0.05).The protective effect of MPP~+-induced neuronal damage was evaluated on the compound isolated from chinese agarwood.At a concentration of 2μM,compound 6,and 11has a very significant protective effect on PC12 cell injure induced by MPP~+(P<0.001),while compound(8)has a very significant protective effect on PC12 cell injure induced by MPP~+(P<0.01).At a concentration of 20μM,compound 1,10,and 28 has a very significant protective effect on PC12 cell injure induced by MPP~+(P<0.001),compound(13)has a very significant protective effect on PC12 cell injure induced by MPP~+(P<0.01),while compounds5 have a significant protective effect(P<0.05).