1. a National Center for Natural Products Research, School of Pharmacy, University of Mississippi, University , MS 38677 , USA
2. b Research Institute of Pharmaceutical Sciences, School of Pharmacy, University of Mississippi, University , MS 38677 , USA
3. c Center for Bottomland Hardwoods Research, USDA-Forest Service, Southern Hardwood Laboratory , Stoneville , MS 38776 , USA
4. d Crop Genetics and Production Research Unit, USDA-ARS , Stoneville , MS 38776 , USA