1. Department of Biology, University of Mississippi , Oxford, Mississippi 38677, USA
2. Natural Products Utilization Research Unit, U.S. Department of Agriculture, Agricultural Research Service , Oxford, Mississippi, USA
3. National Center for Natural Products Research, School of Pharmacy, University of Mississippi , Oxford, Mississippi, USA
4. Division of Pharmacology, Department of BioMolecular Sciences, School of Pharmacy, University of Mississippi , Oxford, Mississippi, USA