Abstract
The leaves of Piliostigma thonningii are used in traditional medicine in Benin to treat inflammatory skin diseases and
infections. So far, pharmacological studies of the anti-inflammatory and anti-infective
effects of phytochemically characterized extracts of P. thonningii have been very limited. Therefore, we investigated the in vitro anti-inflammatory and antimicrobial effect of P. thonningii leaf extracts and analyzed the phytochemical composition of extracts of different
polarities (water, 50% ethanol, and n-hexane). Quercetin-3-O-rhamnoside was confirmed as the main flavonoid in the polar extracts. GC-MS analysis
identified 20 constituents of the aqueous extract and 28 lipophilic compounds of the
n-hexane extract by comparison with authentic standards and spectral library data.
The aqueous P. thonningii leaf extract inhibited the IL-8 and IL-6 secretion in TNF-α-stimulated HaCaT cells in a
concentration-dependent manner with IC50 values of 74 µg/mL for IL-8 and 89 µg/mL for IL-6. However, an inhibitory effect
of the identified quercetin-3-O-rhamnoside and its aglycone, quercetin, on the release of IL-8 and IL-6 could not
be demonstrated. In the antimicrobial screening, inhibition zones for a 50% EtOH leaf
extract of P. thonningii were found for Staphylococcus epidermidis, Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, and Escherichia coli. For none of the microbial strains, however, the MIC was below 500 µg/mL, so that
the antibacterial activity must be classified as low. As a result, our investigations
primarily support the ethnomedical use of P. thonningii leaf extracts in topical inflammatory conditions. Further studies are required to
identify the compounds responsible for the in vitro anti-inflammatory effects.
Key words
Piliostigma thonningii
- Fabaceae - inflammation - antimicrobial - HaCaT
