Woodinine and its Stereomers - Absolute Configuration

The synthesis of all the four stereomers of the alkaloid woodinine ( 12a )¹⁾ is described and the stereochemical conclusions of Païs³⁾ and Still⁶⁾ are discussed. The absol. configurations of woodinine ( 12a ) and its diastereomer 8b are unequivocally deduced from the pertinent piperazinediones 16 and 17 .     

Structure-function relationship of new anthralin derivatives assayed for growth inhibition and cytotoxicity in human keratinocyte cultures.

HaCaT keratinocyte cultures were exposed to twelve hydrophilic anthralin derivatives 1 to 12 with substituents at C-1 and C-8 of the anthrone skeleton, of one H at C-10 and of both H's at C-10 by lacton rings. After 3 microM treatment growth was determined by cellular protein content, 3H-thymidine- and 14C-amino-acid-uptake and cytotoxicity by the release of cytoplasmic LDH into the culture medium. In comparison to acetone control (100%) anthralin suppressed mean protein content, as well as DNA- and protein-synthesis to 33, 28, and 21%, respectively, and the drug revealed an enzyme release of 660%. In relation to the parent drug we found similar cell growth inhibitory effects of compounds 4, 6, 8, 9, 10, and 12. Deriv. 4, 8, and 10 were, however, to some extent less cytotoxic than anthralin, whereas deriv. 6, 9, and 12 were in the same range. An extreme suppression of growth parameters which differed from the anthralin effect by a factor 0.5-0.8 was caused by deriv. 11, showing the same cytotoxicity. Deriv. 1, 2, 3, 5, and 7 did not demonstrate any cytotoxicity. Concerning growth parameters, deriv. 2 induced a slight stimulation, deriv. 3 and 7 were completely ineffective, deriv. 1 and 5 induced slightly to moderately inhibited proliferation but both being much less effective than anthralin. These data indicate that the "minimum structure" concept by Krebs and Schaltegger--claiming 1-hydroxy-9-anthrone as a precondition for clinical antipsoriatic potency--is not valid at least in cell-biological tests and point toward possible usefulness of some experimental model compounds as alternative antipsoriatics.     

Anthralin derivatives--inhibition of 5-lipoxygenase--antipsoriatic efficacy.

Inhibition of 5-lipoxygenase by anthralin (1) and 41 derivatives is determined: the acids 38 and 39, the lactones 40-42 and 9-anthrone (8) are the most potent inhibitors, the lactone 41 reaching the efficacy of nordihydroguaiaretic acid (NDGA). The results were correlated with the hydrophilic/lipophilic balance of the test compounds and their clinical efficacy as far as known. There is no correlation between the "minimum structure" of Krebs and Schaltegger concerning antipsoriatic activity and the inhibitory effects against 5-lipoxygenase.     

Medicinal plants from nepal: evaluation as inhibitors of leukotriene biosynthesis

The methanolic extracts of 25 different Nepalese medicinal plants were tested for their activity to inhibit the biosynthesis of leukotriene B₄ in bovine polymorphonuclear leukocytes. The selected indigenous plants are used in traditional herb remedies to treat inflammatory diseases such as asthma, bronchitis, rheumatism, and skin disorders presumed to be mediated by leukotrienes. The leaves of Zanthoxylum nepalensis were shown to be the most potent inhibitor with an IC₅₀ value of 11 μg/ml. The extracts obtained from Astercantha longifolia and Hedychium ellipticum also exhibited potent inhibitory action with IC₅₀ values of 20 and 22 μg/ml, respectively.     

Metabolism of antipsoriatic anthrone derivatives

The metabolisation of the antipsoriatically active molecules 1,8,9-triacetoxy-anthracene und 1,8-diacetoxy-9-anthrone by serum is described. Under these conditions 1,8-dihydroxy-9-anthrone, 1-hydroxy-8-acetoxy-9-anthrone, 1,8,1',8'-tetrahydroxy-bisanthrone, 1,8-dihyroxy-anthraquinone, 1,8-diacetoxy-anthraquinone and 1-hydroxy-8-acetoxy-anthraquinone arise from both educts. Quantitative determinations of these metabolites indicate that hydrolytic reactions occur prior to oxidation. Contrary to 1,8-dihydroxy-9-anthrone, 1,8,9-triacetoxyanthracene and 1,8-diacetoxy-9-anthrone are effective against psoriatic lesions without accompanying inflammations of the skin. 1,8,9-Trimethoxy-anthracene, however, is ineffective, also indicating that at least 1,8,9-triacetoxy-anthracene is a prodrug.--In agreement with Krebs' hypothesis 10,10-dialkylated 1,8-dihydroxy-9-anthrones described in this paper are ineffective against psoriasis.     

Temporal representation of iterated rippled noise as a function of delay and sound level in the ventral cochlear nucleus

The discharge patterns of single units in the ventral cochlear nucleus (VCN) of anesthetized guinea pigs were examined in response to iterated rippled noise (IRN) as a function of the IRN delay (which determines the IRN pitch) and the IRN sound level. Delays were varied over five octaves in half-octave steps, and sound levels were varied over a 30- or 50-dB range in steps of 5 dB. Neural responses were analyzed in terms of first-order and all-order inter-spike intervals (ISIs). The IRN quasi-periodicity was preserved in the all-order ISIs for most units independent of unit type or best frequency (BF). A deterioration of the temporal all-order code was found, however, when the neural response was influenced by inhibition. The IRN quasi-periodicity was also preserved in first-order ISIs for a limited range of IRN delays and levels. Sustained Chopper units (CS) in the VCN responded with very regular ISIs when the IRN delay corresponded to the unit's chopping period; i.e., the unit showed an increased proportion of intervals corresponding to the IRN delay (interval enhancement) relative to an equal-level, white-noise stimulation. This interval enhancement has a band-pass characteristic with a peak corresponding to the chopping period. Moreover, for CS units in rate saturation, the chopping period, and thus the interval enhancement to the IRN, did not vary with level. Units classified as onset-chopper also show a band-pass interval enhancement to the IRN stimuli; however, they show more level-dependent changes than CS units. Primary-like (PL) units also show level-dependent changes in their ability to code the IRN pitch in first-order intervals. The range of delays where PL units showed interval enhancement was broader and extended to shorter delays. Based on these findings, it is suggested that CS units may play an important role in pitch processing in that they transform a higher-order interval code into a first-order interval place code. Their limited dynamic range together with the preservation of the temporal stimulus features in saturation may serve as a physiological basis for the perceived level independence of pitch.