Chemical Constituents And Their Bioactivity Of Five Plants

Lichens, symbiotic organisms of fungi and algae, synthesize a great number of metabolites, which comprise amino acid derivatives, sugar alcohols, aliphatic acids, monocyclic aromatic compounds, quinones, chromones, xanthones, dibenzofuranes, depsides, depsidones, depsones, terpenoids, steroids and carotenoids. Lichens have been used in folk medicine for the treatment of various diseases in many countries. For example, Cetraria islandica was used to protect against coughing; Lobaria pulmonaria was used to protect against lung desease, Usnea longissima is widely used in the treatment of legs and loin's injuries, bone fractures, and skin eruptions in the folk medicine of different countries. It has also been used widely as an expectorant, for wound dressing and in the treatment of ulcers.Rhodobryum giganteum and R. roseum were named to be "Hui Xin Cao" in the folk. Widely, it has been used in folk medicine for the treatment of cardiovascular diseases, such as hypertension, coronary heart disease (CHD), and atherosclerosis. Previous phytochemical investigations of R. giganteum have demonstrated the presence of terpenoids, steroids, fatty acids, flavanoids and alkloids.By various separation techniques, 14 compounds were isolated from the lichen Sticta nylanderiana and among them 13 compouds were determined on the basis of spectral data (MS, ¹H-NMR, ¹³C-NMR and 2D-NMR), as well as by comparison of their spectral data with those of literature reported values(Table 1). These compounds were ethyl 3-formyl-2,4-dihydroxy-5,6-dimethylbenzoate (1), methyl 2,4-dihydroxy-3, 5, 6-trimethylbenzoate (2), 2,6-dihydroxy-3,4-dimethylbenzal dehyde (3), orsellinic acid (4), methyl orsellinate (5), ethyl orsellinate (6), 3,5-dihydroxytoluene (7), lecanoric acid (8), gyrophoric acid (9), 4-(9-methyl gyrophoric acid (10), retigeric acid B (11), ergosterol (12) and 1-(O-α-D-Gluco-pyranosyl)-3-one-hentriacontaol (13) . Among them compound 1 was a new compound. Compound 2 was isolated from lichen plants for the first time as well as compounds 3～8 and 10-12 were isolated from this species for the first time. The antifungal activities of compounds 6 and 11 were evaluated according to NCCLS method. Using fluconazole as positive control, the MIC₅₀ of compounds 6 and 11 were given to be 128μg/ml and 64μg/ml respectively.From Lobaria kurokawae Yoshim, 9 components were isolated and their structures were elucidated as ergosterol (Sa-1), Stictan-3β, 22α-diol (Sa-2), ethyl orsellinate (Sa-3), 3-O-Methyl-1,2:5,6-bis-O-(1-methyl ethylidene)-d-chiro-inositol (Sa-4), retigeric acid B (Sa-5), retigeric acid A (Sa-6), retigeric ester A (Sa-7) and retigeric ester B (Sa-8) (Table 2). Compounds Sa-7, Sa-8 and Sa-9 were new compounds. Sa-1～Sa-4 were isolated for the first time from this species. And the main component of this plant (compound Sa-5) showed significant antifungal activity. Compounds Sa-5 and Sa-6 were only detected by TLC and HPLC methods previously.From Lobaria yunnanensis Yoshim 5 compounds were obtained and their structures were identified as orsellinic acid (L-l), ethyl orsellinate (L-2), 3, 5-dihydroxytoluene (L-3), lecanoric acid (L-4), and gyrophoric acid (L-5) (Table 3). All these compounds were isolated from this species for the first time.The ethyl ether extract of Ramalina sinensis were analysed by HPLC and 5 compounds were obtained. Among them 2 compounds have been determined as usnic acid (SH1) and lecanoric acid (SH2) (Table 4). Compound SH2 was isolated for the first time from this plant.The chemical components of the moss R. giganteum were studied and the antioxidant activities of four compounds were assessed by the reducing power and free radical scavenging tests. The protective effects against H₂O₂-induced oxidative cardiac cell injury of these four compounds were also evaluated. The ethanol extracts of R. giganteum were chromatographed repeatedly on various columns and 26 compounds were obtained. Among them 22 compounds were determined as: 3,3',5,5'-tetramethoxy-(1,1'-biphenyl) -4,4'-diol (cw-1), 4-hydroxy-3,5-dimethoxybenzoic acid (cw-2), 4-hydroxy-3- methoxy benzoic acid (cw-3), 4-hydroxy-3,5-dimethoxybenzaldehyde (cw-4), 1-(4-hydroxy-3,5- di methoxyphenyl)ethanone ( cw-5),1-(4-hydroxy-3-methoxy phenyl)ethanone (cw-6), 4-hydroxy-3-methoxybenzaldehyde (cw-7), 4-hydroxy benzaldehyde (cw-9), 4-hydroxybenzoic acid (cw-14), ursolic acid (cw15), friedelin (cw16), friedelinol (cw-17), 3-hydroxy-olean-5(6)-ene (cw-18), (E)-4-ethoxy-4- oxobut-2-enoic acid (cw-8), 5-ethoxy-5-oxopentanoic acid (cw-10), 4-oxohexanoic acid (cw-11), (E)-4-hydroxyhex-2-enoic acid (cw-12), tetracosanoic acid (cw-22), 3-hydroxy- 2-methyl-4H-pyran-4-one (cw-13), 5,8-epidioxy-5a,8a-ergosta-6,22E-dien-3β-ol (cw-19),β-sitosterol (cw-20) and daucosterine (cw-21) (Table 5). Among them compounds cw-1 and cw-5 were new natural products, and compounds cw-2～cw-4, cw-6～cw-14, cw-17～cw-19 and cw-22 were isolated for the first time from this species.The antioxidant properties of compounds cw-1,cw-4,cw-5 and cw-7 were evaluated. The reducing power test shows that all the samples have reducing power. The scavaging-activity test shows that the samples can reduce the stable free radical,α,β-diphenyl-β-picrylhydrazyl (DPPH). And the result of flow-cytometric assay of 2', 7'-dichlorodihygrofluorescein(DCFH) shows that the samples have protective effects against oxidative cardiac cell injury induced by H₂O₂. These results may explain the mechanisms of this herb being used as the treatment to cure heart desease in folk medicine. But further studies should be performed to verify them.