The isolation and identification of dermatologically active constituents of coal tar
The production and uses of coal tar are reviewed as are the
uses of steroids and cytotoxic agents in the treatment of psoriasis
with a review of the condition also.
An attempt was made to improve the efficaciousness and cosmetic
acceptability of a low temperature tar, by screening fractions of
this tar, derived from a variety of separation procedures. The most
efficacious fraction was the highest boiling acid fraction, which
is believed to consist mainly of mono- and di-hydric phenols. A
time and concentration study showed that the optimum regime was the
application of a 10% concentration in 5% wool fat in soft, yellow
paraffin daily for 21 days.
The mouse tail skin was selected as an experimental model, to
ascertain the efficaciousness of fractions, because of the similarities
between this skin and the psoriatic lesion. The activity of a
fraction was monitored by the inducement of a granular layer in the
mouse tail epidermis.
Because coal tar is not an easy medium to work with, and the
active fractions showed no increase in cosmetic acceptability over
the parent coal tar, likely coal tar constituents were selected for
screening on the basis of phenolic character, and the molecular
weight range elucidated by mass spectroscopy.
32 potential anti-psoriatic agents were screened on mouse tail.
Two catechols, 3,5-di-t-butyl and 4-t-butyl catechols were active.
Other structures showed little or no activity. 24 catechols were
screened and two extremely active catechols were discovered, 3-methyl-
5-t-octyl and 5-methyl-3-t-octyl catechols.
The screening of catechol-rich coal tar fractions and a coal
tar fraction which had had the catechols removed by oxidation, showed
that some anti-psoriatic activity was contained in the catechol
fraction of coal tar.
Attempts to elucidate the mode of action of these two compounds
met with little success, but two modes of action are suggested.