Bigel formulations of St. John's wort extract in wound healing: toxicological aspects

This study aimed to investigate the toxicological profile of hyperforin (HP) in silico and to assess it in vivo after topical application of an HP-rich St. John's wort (SJW) extract. The former analysis predicted low toxicity because of HP's inability to bind DNA or proteins, but structural alerts for skin irritation/corrosion, carcinogenicity, and mutagenicity were found. Animal studies involved the treatment of excision wounds in Wistar rats with poloxamer 407/borage oil formulations (bigels; Bs) containing HP-rich SJW extract previously developed by us. The effects of semisolids comprising 'free' extract (B/SJW) or extract loaded in nanostructured lipid carriers (B/NLC-SJW) were compared to positive (commercial herbal product) and negative (untreated) controls after 2-, 7-, 14-, and 21-day applications. Malondialdehyde (MDA) and ABTS assays evaluated the degree of oxidative stress-treatment with bigels did not affect MDA favorably but led to an increased radical-cation scavenging capacity (compared to controls). Gamma-glutamyl transferase (GGT), aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT), and lactate dehydrogenase (LDH) enzyme levels were measured as indicators for liver/tissue damage. Treatment with both B/SJW and B/NLC-SJW for 21 days resulted in lower GGT and ASAT levels than those in controls. Two-day application of the biphasic semisolids contributed to normalized ALAT levels (lower than in both negative and positive controls), and the same trends were observed in LDH levels after a 7-day treatment. The promising results obtained after the B/NLC-SJW application suggest that this drug delivery system may not only preserve HP in SJW extract effectively but also 'expose' its cyto-/hepatoprotective potential.