" which is the dried stem of genus Dendrobium, has been used to treat fever, inflammation, and similar conditions. 1,2) Within genus Dendrobium, Dendrobium nobile LINDL. and D. officinale K. KIMURA et MIGO were originally used as "Xiao Huang Cao Shi Hu." However, these plants are very rare, and therefore, other plants of genus Dendrobium, including D. loddigesii ROLFE, D. moniliforme (L.) SW., and D. lohohense TANG et WANG, have also been distributed as "Xiao Huang Cao Shi Hu" in medicinal herb markets in China. D. loddigesii parasitic on the trees and the rocks in Laos to South China.During our screening of herbal medicines for active compounds with inhibitory activities against nitric oxide (NO) production, some plants of the genus Dendrobium were found to be as active as the herbal medicines.3) Thus, we investigated 80% MeOH extracts of D. loddigesii in order to isolate inhibitors of NO production. New phenanthrenes, loddigesiinols A (1) and B (7), and stilbenes, loddigesiinols C (8) and D (9), were isolated from the active portions, i.e., the n-hexane and EtOAc extracts, along with known compounds, including five phenanthrenes, three stilbenes, two lignans, and three sterols. Here, we describe the isolation and structure determinations of the new compounds, loddigesiinols A (1) and B (7) and loddigesiinols C (8) and D (9), and evaluate their effects against NO production and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging.The 80% MeOH extract of D. loddigesii was partitioned in succession with n-hexane, EtOAc, and n-BuOH. The EtOAc extract, which showed strong inhibitory activity against NO production (inhibition rate: 43.4% at 30 mg/ml), was chromatographed on a silica gel column, and then purified using normal and reverse phase HPLC to obtain compounds 9-12 and 16-18. Another active fraction, n-hexane extract (inhibition rate: 43.6% at 30 mg/ml), was also separated by normal and reverse phase column chromatography, and then purified by HPLC to obtain compounds 1-8 and 13-15. Compounds 2-6 and 10-18 were found to be identical to moscatin 4) (plicatol B 5) ), 5-hydroxy-2,4-dimethoxyphenanthrene, 6) lusianthridin, 7) rotundatin 8) (plicatol C 5) ), hircinol, 9) moscatilin 10) (aloifol II 11) ), gigantol, 12) batatasin III, 11) stigmasterol, b-sitosterol, sitostenone, dehydrovomifoliol, 13) (Ϫ)-pinoresinol, 14) and (Ϫ)-medioresinol, 15) respectively, by comparisons with spectroscopic data from the existing literature.Loddigesiinol A (1) was obtained as a pale brownish amorphous powder. Its molecular formula was determined to be C 16 H 14 O 3 by high resolution (HR)-electron ionization (EI)-mass spectra (MS). The UV spectrum showed absorption peaks at 211, 259, 282, 315, and 362 nm, indicating the presence of a phenanthrene skeleton. 16) In the IR spectrum, absorption at 3286 cm Ϫ1 indicated hydroxy groups. 1 H-NMR revealed meta-coupled signals at d H 6.81 (d, Jϭ2.4 Hz) and 6.99 (d, Jϭ2.4 Hz), indicating the presence of a tetrasubstituted phenyl group; a spin system at d H 7.13 (dd, Jϭ7.5...

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