Traditionally, the hot oil extraction of YaSP has been intensively used in the treatment of chronic wounds, which invariably result in biofilm-associated bacterial infections. This study is the first work that explored the traditional form of YaSP, a complex herbal medicine, instead of its extracts. The anti-biofilm activity of YaSP on both hydrophobic and hydrophilic surfaces might be partly associated with the presence of α-mangostin in the formula. The anti-Pseudomonas biofilm activity of the herbal formula could also be effective in the prevention J. Chokpaisarn et al. Microbial Pathogenesis 128 (2019) 354–362 361 of the development and growth of many other pathogens found in chronic wounds such as Staphylococcus spp. and Enterococcus spp.