Manfreda maculosa Leaf Extracts and Their Effects on Whole and Selected Myotoxic Components in Crotalid Venom

Manfreda spp have been used for the treatment of snakebite by several cultures in North and Central America (Austin & Honychurch, 2004, Johnson, 1999, Moerman, 2008, Verhoek, 1978a). There has been no systematic study of the genus Manfreda for its usefulness in the treatment of snakebite. While the annual incidence of snakebite in the United States is relatively low (approximately 8,000–10,000), with a low mortality rate of 5–6 cases per year, there is still significant morbidity associated with snakebite (CDC–NIOSH, 2018, Springhouse Corp (eds), 2005). Worldwide numbers of the cases of snakebite can only be estimated and run as high as 1,841,000 cases with fatalities as high as 94,000 (Kasturiratne et al., 2008). Currently the only treatment for snakebite consists of antivenom administration in a hospital setting due to the possibility of an anaphylactic response. A plant-based treatment could have fewer reactions and provide onsite treatment for snakebite injuries thus possibly lowering the morbidity of the local tissue effects (Houghton, 1994). An aqueous extract of Manfreda maculosa leaves was examined to see if it could mitigate the effects of whole venom obtained from Crotalus viridus viridus in an in vitro study using human skeletal muscle cells. Experiments measuring cell death using differential nuclear staining and experiments examining cell proliferation using human skeletal myoblasts or differentiated myocytes (myotubes) were performed. While the clinical picture of envenomation shows tissue necrosis, this study found no cell death, neither necrosis nor apoptosis, occurring in venom-treated HuSKM myoblasts and myocytes or necrosis with the myotoxins in the same cells using the methods employed. The aqueous extract of Manfreda maculosa leaves was not reliably found to offer any protection from rattlesnake evenomation. However, previous research had not used human skeletal muscle cells or a cell proliferation assay within the setting of venom toxicity studies. The further use of these technologies may prove useful in elucidating venom toxicity