1. Natural Products Division, Department of Chemistry, Sri Venkateswara University, Tirupati 517 502, India
2. National Institute of Animal Biotechnology, Hyderabad 500 049, India
3. School of Life Sciences, University of Hyderabad, Hyderabad 500 046, India
4. Laboratoire de Chimie et Biochimie des Substances Naturelles, USM 0502 MNHN-UMR 5154, CNRS, 63 rue Buffon, Paris 75005, France