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DOI: 10.1055/a-1229-4565
Phytochemical Analysis, In Vitro Anti-Inflammatory and Antimicrobial Activity of Piliostigma thonningii Leaf Extracts from Benin
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.
Supporting Information
- Supporting Information
HPLC fingerprint profiles of PTEE at UV 254 nm and 352 nm and a summary of the chromatographic, UV-Vis-spectroscopic, and mass spectrometric characteristics of the compounds identified from the extract are provided as Supporting Information. Furthermore, there is a GC-MS chromatogram of the n-hexane extract of P. thonningii leaves and a table with the identified compounds. In addition, a figure of the metabolic activity of HaCaT cells after co-incubation with PTAE and stimulation with TNF-α is available as Supporting Information.
Publication History
Received: 08 March 2020
Accepted after revision: 20 July 2020
Article published online:
08 September 2020
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