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The methanolic extract and its subfractions from red peony root, the dried roots of Paeonia lactiflora Pallas showed potent antiallergic effects, as inhibition of immunoglobulin E (IgE)-mediated degranulation in rat basophil leukemia (RBL)-2H3 cells. Bioassay-guided fractionation led to the isolation of 16 monoterpene derivatives, including 3 new compounds, paeoniflorol ( 1 ), 4′-hydroxypaeoniflorigenone ( 2 ) and 4- epi -albiflorin ( 3 ), together with 13 known ones ( 4–16 ). The chemical structures of the new compounds were elucidated on the basis of spectroscopic and chemical evidences. Among the isolated monoterpene derivatives, nine compounds showed potent anti-allergic effects and compound 1 was the most effective. A primary structure-activity relationship of monoterpene derivatives was discussed. [ABSTRACT FROM AUTHOR]

The phytochemical investigation of natural products of Gynura divaricata led to the isolation of eleven caffeoylquinic acid derivatives. They were characterized by spectrometric methods as 5- O -caffeoylquinic acid ( 1 ), 5- O - p -coumaroylquinic acid ( 2 ), 5- O -feruloylquinic acid ( 3 ), methyl 5- O -caffeoylquinate ( 4 ), 3,4-dicaffeoylquinic acid ( 5 ), 3,5-dicaffeoylquinic acid ( 6 ), 4,5-dicaffeoylquinic acid ( 7 ), methyl 3,4-dicaffeoylquinate ( 8 ), methyl 3,5-dicaffeoylquinate ( 9 ), methyl 4,5-dicaffeoylquinate ( 10 ) and ethyl 4,5-dicaffeoylquinate ( 11 ). The individual compounds were screened for the inhibition of yeast α-glucosidase and Protein Tyrosine Phosphatase 1B (PTP1B) using in vitro assays. Among the isolated compounds, 3,4-dicaffeoylquinic acid ( 5 ), 4,5-dicaffeoylquinic acid ( 7 ), methyl 3,4-dicaffeoylquinate ( 8 ) and methyl 4,5-dicaffeoylquinate ( 10 ) exhibited significant inhibitory activities against α-glucosidase. In addition, 5- O - p -coumaroylquinic acid ( 2 ), 3,5-dicaffeoylquinic acid ( 6 ) and 4,5-dicaffeoylquinic acid ( 7 ) had considerable inhibitory effect against PTP1B. Based on these findings, the caffeoylquinic acid derivatives were deduced to be potentially responsible for the anti-diabetic activity of G. divaricata . The preliminary structure–activity relationship study suggests that the number and positioning of caffeoyl groups in the quinic acid derivatives are important for both α-glucosidase and PTP1B inhibitory potency. Moreover, the corresponding methyl esters of some dicaffeoylquinic acids have enhanced inhibitory activity against yeast α-glucosidase. [ABSTRACT FROM AUTHOR]