Anti-oxidant and anti-inflammatory compounds from Magnolia liliifera (L.) Baill. flower and dendrobium signatum Rchb.f.

Abstract

In this study, a purification of the EtOAc crude extract of Dendrobium signatum Rchb.f. aerial parts was performed fifteen compounds (1-15) and the hexane crude extracts of Magnolia liliiferra (L.) Baill. were further isolated to accomplish three compounds (16-18). They yielded one new picrotoxane sesquiterpene, 7-hydroxydendroterpene B (2) and a new a-pyrone, (-)-6R-signatone (4), along with sixteen known compounds. These included dendroxine (1), crystallinin (3), dendrocandin B (5), dendrocandin I (6), 6''-de-O-methyldendrofindlaphenol A (7), p-hydroxyphenylethyl-p-coumarate (8), 3,4-dihydroxy-5,4'-dimethoxybibenzyl (9), 3-methoxy-5-[2-(4-methoxyphenyl) ethyl]phenol (10), 4,4'-dihydroxy-3,5-dimethoxybibenzyl (11), naringenin (12), (2S)-homoeridodictyol (13), (2S)-homohesperetin (14), (-)-syringaresinol (15), (+) sesamin (16), (+) fargesin (17) and (-) kobusin (18). Their structures of new compounds were elucidated through by analysis of spectroscopic data and single-crystal X-ray diffraction analysis, whereas those of the known ones were identified by comparison of their data in the literature. Afterward, all the extracted isolated compounds were evaluated for antioxidant activity using the DPPH and ABTS free radical scavenging assay. The results showed that the new (-)-6R-signatone 4 exhibited very promising ABTS scavenging activity with IC50 of 0.71 ± 0.01 µM in comparison with a positive control Trolox® (IC50 of 27.26 ± 0.33 µM). Furthermore, the dimer bibenzyls (5-7) along with compounds 3. 4, 8, 9 and 17 were promising to inhibit the lipid peroxidation in range (53-70 %) in the vital model at concentration 5 µM. For the anti-inflammatory activity, among all the compounds, it was found that lignans, (-) kobusin 18 (IC50 of 4.72 ± 0.17 µM) significantly enhanced the NO production inhibition activity. Similarly, phenylpropanoids, p-hydroxyphenylethyl-p-coumarate 8 also displayed the high potent inhibition with IC50 of 6.18 ± 0.50 µM as compared to the standard indomethacin (IC50 of 28.42 ± 3.51 µM).