Fertility Affects Yield and Emodin Levels but Not Catechin Concentrations in Red-Veined Sorrel (Rumex sanguineus L.)

Species in the genus Rumex (Polygonaceae family) have been wild-harvested and cultivated for their medicinal, culinary and dyeing properties. We exposed one of those species, Rumex sanguineus (red-vein sorrel) to varying rates of nitrogen and phosphorus fertilization in a controlled greenhouse experiment to measure the accumulation of emodin, aloe-emodin, and chrysophanol and catechin in young plants. Even though anthraquinones are found throughout the genus Rumex , we could only reliably extract emodin and catechin from the plants we produced. The low levels of catechin and the anthraquinone emodin we observed were satisfactorily used in fabric dyeing. Further investigation should ascertain if anthraquinones and catechin levels are higher in mature leaves as well as in other plant parts such as roots. Higher levels of anthraquinones and catechin than what we observed in young leaf tissue may make the dyeing process potentially more efficient. Our work also established proper fertilizer regimens for newly transplanted red-vein sorrel. Maximum fresh weight, dry weight, and emodin were observed in nitrogen treatments at and above 200 mg·L −1 nitrogen, whereas fresh weight positively responded to increasing phosphorus fertilizer from 0 to 40 mg·L −1 phosphorus. No interaction between nitrogen and phosphorus fertility levels was found, nor was there any effect of fertilizer application on catechin content. Based on our work, we suggest Rumex sanguineus should be grown in early development at 200 mg·L −1 nitrogen and 10 mg·L −1 phosphorus of a complete fertilizer to maximize fresh weight and dry weight plants for culinary, medicinal, and dyeing purposes.