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The conjugation of terpenes with phloroglucinol derivatives31, as well as the formation of monoterpene glucose esters32, leads to the myriad of defence compounds that vary across the genus.

Councler substitutes phloroglucinol for pyrogallol, with the advantage of doing away with the digestion at high temperature.

The presence of diresorcinol is without influence on the result, provided a sufficient excess of actual phloroglucinol is employed.

Sulphonation of phloroglucinol succeeds at higher temperatures only, the sulphonic acid being a solid which is scarcely soluble in water, the latter then assuming a wine-red colour.

Of the trihydroxybenzenes pyrogallol and phloroglucinol only were included in these investigations.