Oil from the wild roots of North India is said to be highly levorotatory (rotates the plane of polarized light to the left), whereas that from the cultivated roots from South India is dextrorotatory (rotates polarized light to the right).    From Wordnik.com.  [4 Questions and Answers] Reference

The '265 patent discusses the unusual stereoselectivity of the biological properties as between the dextrorotatory and the levorotatory enantiomers.    From Wordnik.com.  [Patent Baristas] Reference

Believing that there was no advantage to separation of the enantiomers of thienopyridines, and no other racemates were separated until November 1985 when Sanofi then determined the biological properties of the enantiomers of PCR 4099, and found that they had the rare characteristic of "absolute stereoselectivity": the dextrorotatory enantiomer provided all of the favorable antiplatelet activity but with no significant neurotoxicity, while the levorotatory enantiomer produced no antiplatelet activity but virtually all of the neurotoxicity.    From Wordnik.com.  [Patent Baristas] Reference