Effect of altitude on picroside content in core collections of Picrorhiza kurrooa from the north western Himalayas

Picrorhiza kurrooa Royle ex Benth (Scrophulariaceae), commonly known as Kutki, is a major ingredient of many ayurvedic preparations prescribed in the treatment of various diseases. Picrosides I and II are the active agents responsible for the medicinal effects of Kutki, and the variation in content of these compounds in plants at different altitudes is a major question to be addressed. The picroside I and II content in various plant parts of P. kurrooa collected from different altitudes, viz. Sonemarg (2,740 m a.s.l.), Tangmarg (2,690 m a.s.l.), and Pulwama (1,630 m a.s.l.) in the north-western Kashmir Himalayas was analyzed by HPLC. A considerable degree of variation in picroside content was observed. Picroside I and II was highest in populations collected from Sonemarg followed by Tangmarg, suggesting that picroside accumulation is directly correlated with altitudinal change. More picroside I was found in the rhizome and roots of the Pulwama population as compared to Tangmarg samples, whereas the quantity of Picroside II was reduced in plants from Pulwama compared to the Tangmarg population, suggesting that cultivation of P. kurroa at lower altitude reduces the picroside content. The quantities of picrosides also varied spatially, being highest in rhizome followed by roots, inflorescence and leaves in the populations from all three locations. The study concludes that picroside I and II accumulation depends on altitude, which could help in the selection and collection of superior genotypes with uniform effects for utilization by the pharmaceutical industry.