[Studies on chemical constituents from herbs of Taraxacum mongolicum].

OBJECTIVE: To investigate the chemical constituents of the herbs of Taraxacum mongolicum. METHOD: The chemical constituents were isolated by various column chromatographic methods and their structures elucidated mainly by NMR and MS evidences. RESULT: Forty-four components were obtained and identified were as artemetin (1), quercetin (2), quercetin-3', 4', 7-trime-thyl ether (3), luteolin (4), luteolin-7-O-beta-D-glucopyranoside (5), luteolin-7-O-beta-D-galactopyranoside (6), genkwanin (7), isoetin (8), hesperetin (9), genkwanin-4'-O-beta-D-lutinoside (10), hesperidin (11), quercetin-7-O-[beta-D-glucopyranosyl (1-->6) -beta-D-glucopyranoside (12), quercetin-3, 7-O-beta-D-diglucopyranoside (13), isoetin-7-O-beta-D-glucopyranosyl- 2'-O-alpha-L-arabinopyranoside (14), isoetin-7-O-beta-D-glucopyranosyl-2'-O-alpha-D-glucopyranoside (15), isoetin-7- O-beta-D-glucopyranosyl-2'-O-beta-D-xyloypyranoside (16), caffeic acid (17), furulic acid (18), 3-O-caffeoylquinic acid (19), 3, 5-di-O-caffeoylquinic acid (20), 3, 4-di-O-caffeoylquinic acid (21), 4, 5-di-O-caffeoylquinic acid (22), 1-hydroxymethyl-5-hydroxy-phenyl-2-O-beta-D-glucopyranoside (23), p-hydroxybenzoic acid (24), p-coumaric acid (25), 3, 5-dihydroxylbenzoic acid (26), gallic acid (27), gallicin (28), syringic acid (29), 3, 4-dihydroxybenzoic acid (30), caffeic acid ethyl ester (31), esculetin (32), rufescidride (33), mongolicumin A [6, 9, 10-trihydroxy-benzoxanthene-1, 2-dicarboxylic acid] (34), mongolicumin B [1 l-hydroxy-2-oxo-guaia-1 (10), 3, 5-trien-8, 12-lactone] (35), isodonsesquitin A (36), taraxacin (37), sesquiterpene ketolactone (38), taraxasteryl acetate (39), phi-taraxasteryl acetate (40) and lupenol acetate (41), palmitic acid (42), beta-sitosterol (43), and stigmasterol (44). CONCLUSION: Four compounds (14, 15, 34 and 35) were new compounds, compounds 1, 3, 6-13, 20-22, 30 and 31 were isolated from this genus for the first time, while compounds 18, 23-29, 32 and 37-42 were obtained from this species for the first time.

Three-dimensional Tri-SNSs-layered electrodeposited reduced graphene oxide for ECL biosensing of DNA.

In this study,we proposed a triangular silver nanosheets (Tri-SNSs)-layered, Chitosan (CS)-supported three-dimensional of reduced graphene oxide (3D-ERGO) electrochemiluminescence (ECL) biosensing platform using self-designed dual-Ru(bpy)32+ scDNA (Ru2-DNA) as capture probe for ECL biosensing of single-chain DNA (scDNA). Based on the different affinity with scDNA and double chain DNA (dcDNA), the biosensor is designed to recognize the target DNA (t-DNA), which leads to the desorption of a hybrid molecule from the surface of the biosensor, further removing the Ru2-DNA and inhibiting the ECL. Analytical results clearly showed that the electrochemical and ECL behaviors of proposed biosensing platform on the glassy carbon electrode (GCE) exhibited outstanding performance, which was due to large specific surface area, high carrier mobility and strong π-π non-covalent attraction toward single-chain DNA (scDNA) of the stable 3D platform, and ECL amplification of Tri-SNSs. Besides, based on such a system, this strategy can effectively identify full match and mismatched target DNA (M-DNA) with a wide concentration range beyond 7 orders of magnitude and detection limit down to 16.2 aM. Therefore, the 3D biosensing strategy shows potential for the application of bioassays.