You may want to check with the Botanical Garden of Kolkata...they have a reference library and are cultivating over 100 medicinal and wild herbs...perhaps, since it is a native plant, they can give you a positive ID.
I also ran across the Botanic Survey of India, based in Kolkata...here is some contact info for them.
Sorry, I may have gotten the math wrong. I was thinking that 100 Rupees was equivalent to a little less than $2.00US. We are so used to paying surcharges and taxes on things here that I did not consider the difference in cost.
I'm not sure I understand prickly. The new foliage being purple reminds me of some of the Solanums. Considering Kolkata is in a quite tropical area and the botanical garden would have a good working knowledge of local plants, I'd say themoonhowl's suggestion is a good one.