Altitudinal variability in anthraquinone constituents from novel cytotypes of Rumex nepalensis Spreng-a high value medicinal herb of North Western Himalayas

Rumex nepalensis is a reputed medicinal herb of North Western Himalayas. It owes its pharmacological significance to an active class of compounds known as anthraquinones. In the present study four different intraspecific cytotypes with varying ploidy level ranging from tetraploidy (4×, 2n = 40) to octaploidy (8×, 2n = 80) were discovered, hitherto unreported. The investigation also included the evaluation of chemical variability in four major anthraquinone constituents of different cytotypes from five altitudinal habitats of Himalayas using standard HPLC method. There was significant increase in the aglycone components of anthraquinones with the increase in ploidy status, except for dodecaploid type (12×, 2n = 120) that showed a decreasing trend in their accumulation. However, the overall concentration of anthraquinones, both glycone and aglycone constituents was found to be highest (33.95%) in the dodecaploid type from Lidderwatt location. Polyploidy, an important driver of eukaryotic evolution is a prevalent feature among angiosperm species providing dynamic genome flexibility to them. Polyploids can undergo rapid structural and functional alterations, allowing them to adapt and persist across heterogeneous landscapes in the long run. It is reflected in the robust adaptability of different cytotypes of R. nepalensis. These display appreciable chemical variability, and ecological plasticity possibly because of the intraspecific polyploidization in response to different ecological niches of a geographical region. The scope of present investigation also extends to identify elite cytotypes in terms of their desirable chemoprofiles for pharmaceutical and commercial purposes.