Lignan derivatives from Krameria lappacea roots inhibit acute inflammation in vivo and pro-inflammatory mediators in vitro.

The roots of Krameria lappacea are used traditionally against oropharyngeal inflammation. So far, the astringent and antimicrobial properties of its proanthocyanidin constituents are considered to account for the anti-inflammatory effect. The aim of the present study was to characterize pharmacologically a lipophilic extract of K. lappacea roots and several isolated lignan derivatives (1-11) in terms of their putative anti-inflammatory activity. The dichloromethane extract (ID50 77 µg/cm²) as well compounds 1-11 (ID50 0.31-0.60 µmol/cm²) exhibited topical antiedematous properties comparable to those of indomethacin (ID50 0.29 µmol/cm²) in a mouse ear in vivo model. Two of the most potent compounds, 2-(2-hydroxy-4-methoxyphenyl)-5-(3-hydroxypropyl)benzofuran (5) and (+)-conocarpan (7), were studied regarding their time-dependent edema development and leukocyte infiltration up to 48 h after croton oil-induced dermatitis induction, and they showed activity profiles similar to that of hydrocortisone. In vitro studies of the isolated lignan derivatives demonstrated the inhibition of NF-κB, cyclooxygenase-1 and -2, 5-lipoxygenase, and microsomal prostaglandin E2 synthase-1 as well as antioxidant properties, as mechanisms possibly contributing to the observed in vivo effects. The present findings not only support the ethnopharmacological use of K. lappacea roots but also reveal that the isolated lignan derivatives contribute strongly to the anti-inflammatory activity of this herbal drug.

Differential and stereoselective in vitro cytotoxicity of eremophilane sesquiterpenes of Petasites hybridus rhizomes in rat hepatocytes.

We tested two CO (2) extracts of Petasites hybridus L. rhizomes, A (rich in furanoeremophilanes) and B (rich in petasins), for IN VITRO cytotoxicity in rat hepatocytes by means of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay (EC (50) values of 0.64 mg/mL for A and 0.32 mg/mL for B). Eight eremophilane sesquiterpene lactones (SL) (1- 8) and one petasin (9) isolated from A were nontoxic or showed moderate cytotoxicity. The presence and type of the ester side chain most probably control the extent of cytotoxicity of the eremophilanolides. (8 R)-2-[(angeloyl)oxy]eremophil-7(11)-en-12,8-olide (1) damaged the hepatocytes most. The 8 α-stereoisomers of both 8-H epimeric couples of the 2-angeloyloxy- and 2-methacroyloxy-esters seem to be more cytotoxic (up to approx. 10-fold) than the corresponding 8 ß-H stereoisomers. Moreover, the results of the MTT assay depended on the cell density being more pronounced with both 8 α-stereoisomers. Further investigations were conducted to study the influence of the stereochemistry on cell respiration, energy metabolism, and membrane integrity [release of lactate dehydrogenase (LDH)] with both couples of the 2-angeloyloxy- and 2-methacroyloxy-esters. In the LDH-leakage assay, (8 R)-2-[(methacroyl)oxy]eremophil-7(11)-en-12,8-olide (2) was the most toxic eremophilane. The stereoselectivity of cell damage of some SL points to a specific, yet unidentified molecular cytotoxicity target.

Absolute configuration of eremophilane sesquiterpenes from Petasites hybridus: comparison of experimental and calculated circular dichroism spectra.

In-depth conformational analyses of 10 known eremophilane (= (1S,4aR,7R,8aR)-decahydro-1,8a-dimethyl-7-(1-methylethyl)napththalene) sesquiterpenes, 1-10, from Petasites hybridus were performed with molecular mechanics as well as density functional theory methods. Electronic transition energies and rotational strengths of these eight eremophilane lactones and two petasins were calculated by time-dependent density functional theory (B3PW91/TZVP). The absolute configurations of the constituents could be assigned by comparison of their simulated and experimental circular dichroism (CD) spectra in methanol as (4S,5R,8S,10R) (1, 2), (2R,4S,5R,8S,10R) (3, 4, 5), (2R,4S,5R,8R,9R,10R) (6), (2R,4S,5R,8R,10R) (7, 8), and (3R,4R,5R) (9, 10). Single-crystal X-ray diffraction data of 8beta-hydroxyeremophilanolide ((8S)-8-hydroxyeremophil-7(11)-en-12,8-olide) (1) served as starting point for the theoretical conformational calculations of the 8beta-epimers of the eremophilane lactones. Experimental CD spectra as well as (1)H NMR spectra of compound 1 in methanol were considerably dependent on sample concentration.

Design and synthesis of ten biphenyl-neolignan derivatives and their in vitro inhibitory potency against cyclooxygenase-1/2 activity and 5-lipoxygenase-mediated LTB4-formation.

A set of ten derivatives of methylhonokiol, an anti-inflammatory active biphenyl-type neolignan from Magnolia grandiflora, has been evaluated for their in vitro cyclooxygenase-1/2 (COX-1/2) inhibitory activity using assays with purified prostaglandin H synthase (PGHS)-1 and PGHS-2 enzymes as well as for their 5-lipoxygenase (5-LOX) mediated LTB(4) formation inhibitory activity using an assay with activated human polymorphonuclear leukocytes. The derivatization reactions included methylation, acetylation, hydrogenation, epoxydation and isomerization. Five of the derivatives are new to science. The most active compound against COX-1 and COX-2 was methylhonokiol with IC(50) values of 0.1 microM, whereas the most active compound against LTB(4) formation was (E)-3'-propenyl-5-(2-propenyl)-biphenyl-2,4'-diol with an IC(50) value of 1.0 microM. Structure-activity relationship studies showed that the polarity of the derivatives plays a crucial role in their activity towards COX-1/2 enzyme and 5-LOX mediated LTB(4) formation.

Discovering COX-inhibiting constituents of Morus root bark: activity-guided versus computer-aided methods.

The aim of this study was to compare the efficiency of two well known approaches for the discovery of the bioactive principle/s in medicinal plants, namely the activity-guided isolation versus the computer-aided drug discovery by means of virtual screening (VS) techniques. Morus root bark of Morus sp. L. (Moraceae) was selected as application example for the discovery of compounds with anti-inflammatory activity. The two cyclooxygenase isoenzymes COX-1 and COX-2 were chosen as targets and the corresponding pharmacophore models were generated by our research. The activity-guided fractionation of the methanol extract of the root bark resulted in the isolation of nine compounds. Their structures were elucidated by mass spectrometry, 1- and 2-dimensional NMR experiments and identified as moracins B, M, the regioisomers O/P as a mixture, and sanggenons B, C, D, E and O. The COX-1 and COX-2 inhibiting activities of these compounds were established in an enzyme assay and compared with the predicted hits obtained from the VS. Sanggenons C, E, and O, that were tested the first time for an inhibitory effect on COX-1 and -2, showed IC50 values of 10-14 microM, and 40-50 microM, respectively. The results show that the COX activities obtained for the sanggenons are correctly predicted by the in silico filtering experiment. In the case of the isolated moracins, however, it failed because the COX inhibiting activities of moracins M and P/O were not retrieved by the VS. Structure-activity relationships of the isolated compounds are discussed as well as potential pitfalls and advantages of the applied strategies.

Synthesis and biological evaluation of a new class of acyl derivatives of 3-amino-1-phenyl-4,5-dihydro-1H-pyrazol-5-one as potential dual cyclooxygenase (COX-1 and COX-2) and human lipoxygenase (5-LOX) inhibitors.

A series of acyl derivatives of 3-amino-1-phenyl-4,5-dihydro-1H-pyrazol-5-one as potential human 5-LOX and COX 1 and COX-2 inhibitors structurally related to the 1-phenyl-3-pyrazolidinone (phenidone, 1) have been synthesized and the activity against COX-1, COX-2 and human 5-LOX enzymes has been evaluated. All the derivatives showed poor activity against enzymes. These data, together with our previous studies, indicated that phenidone and related compounds are not suitable as human 5-LOX inhibitors and that pyrazoline nucleus should not be considered a good scaffold for inhibitors of human 5-LOX enzyme, suggesting the necessity to revisit the proposed mechanism of action of phenidone (1) in human models.

Synthesis and biological evaluation of new phenidone analogues as potential dual cyclooxygenase (COX-1 and COX-2) and human lipoxygenase (5-LOX) inhibitors.

A new series of potential human 5-LOX inhibitors structurally related to the 1-phenyl-3-pyrazolidinone (phenidone, 2) has been synthesized and the activity against COX-1, COX-2, and human 5-LOX enzymes has been evaluated. In contrast with literature data, we observed that phenidone resulted to be inactive against human 5-LOX, while retains its activity against cyclooxygenases in a micromolar range. The present results suggest that the substitution of the amino function at the 4-position is detrimental in terms of activity toward COX-1 and COX-2, while the presence of a double bond at the 4,5-position does not alter the biological profile against COX. The absence of activity vs. human 5-LOX strongly suggests a re-consideration of phenidone and its analogs as 5-LOX inhibitors in humans.