Abstract
The anthranoid composition in roots of Rheum officinale has been followed during a one year cycle. No statistical correlation could be found between total anthranoid content and time of sampling. The mean total anthranoid content was found to be 3.17%, calculated on freeze dried plant material.
On the other hand the ratio anthrone/total anthranoid varied with the season. It was concluded that all anthranoids were present under oxidized form, the anthraquinone, in summer months. They were in the reduced form, the anthrone, in winter. The conversion occured in a time lapse of three weeks.
Also cyclic variations between the relative amounts of anthrone aglycones, anthronemono- and diglycosides could be observed. Just before the conversion anthrone → anthraquinone and vice versa, the anthrone diglycoside content increased markedly.
To find out if ambient temperature decrease is one of the factors influencing the anthraquinone → anthrone conversion, analyses were carried out on plants submitted to a cooling treatment. After comparison with reference plants, it was clear that the composition was similar to that of plants harvested in winter time. This experiment confirms that the conversion anthraquinone → anthrone could be induced artificially by decreasing ambient temperature.
Key Word Index
Rheum officinale - Polygonaceae - Anthraquinones - Anthrones - Cyclic variation
