Leaves from Combretum collinum Fresen (Combretaceae) are commonly used for the treatment of inflammatory conditions, wound healing and bacterial infections in traditional West African medicine. This research focuses on the characterization of the phenolic profile and lipophilic compounds of leaves extracts of C. collinum. Studies of the in vitro anti-inflammatory activity were performed in TNFα stimulated HaCaT cells and antibacterial activity was evaluated with agar well diffusion and microdilution assays. Antioxidant activity was determined by DPPH and ABTS assays and compared to standards. The phytochemical studies confirmed myricetin-3-O-rhamnoside and myricetin-3-O-glucoside as major components of the leaves extracts, each contributing significantly to the antioxidant activity of the hydrophilic extracts. GC-MS analysis identified 19 substances that were confirmed by comparison with spectral library data and authentic standards. Combretum collinum aqueous leaves extract decreased pro-inflammatory mediators in TNFα stimulated HaCaT cells. Further investigations showed that myricetin-3-O-rhamnoside has an anti-inflammatory effect on IL-8 secretion. In the antimicrobial screening, the largest inhibition zones were found against S. epidermidis, MRSA and S. aureus. MIC values resulted in 275.0 µg/mL for S. epidermidis and 385.5 µg/mL for MRSA. The in vitro anti-inflammatory, antibacterial and antioxidant activity supports topical use of C. collinum leaves extracts in traditional West African medicine.

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. Received: 08 March 2020 Accepted after revision: 20 July 2020 Publication Date: 08 September 2020 (online) © 2020. Thieme. All rights reserved. Georg Thieme Verlag KG Stuttgart · New York

In der Zone südlich der Sahara gibt es etwa 7000 verschiedene Pflanzenarten, die ein großes Potenzial haben, zur Ernährungs- und Gesundheitsversorgung der 1,2 Milliarden Einwohner dieser Region beizutragen. Besonders in Benin, einem Staat in Westafrika, sind Heilpflanzen eine wichtige natürliche Ressource, die 80–99 % der Bevölkerung mindestens als ergänzende, wenn nicht sogar als primäre medizinische Grundversorgung nutzen. Blätter von Combretum collinum Fresen. (Combretaceae) werden in der traditionellen westafrikanischen Medizin zur Behandlung bakterieller Infektionen und zur Förderung der Wundheilung eingesetzt. Die vorliegende Untersuchung konzentriert sich auf die phytochemische Charakterisierung und die Analyse der antimikrobiellen Aktivität eines 50 % EtOH-Blattextraktes von C. collinum. Untersuchungen zur antimikrobiellen Aktivität wurden mit Agar-Well-Diffusions- und Mikrodilutionstests durchgeführt. Die phytochemische Charakterisierung erfolgte mit verschiedenen chromatographischen und spektroskopischen Methoden (HPLC, LC-MS, Flash-Chromatographie, ¹H-NMR). Die Untersuchungen bestätigten Myricetin-3-O-rhamnosid und Myricetin-3-O-glucosid als polyphenolische Hauptinhaltsstoffe des 50 % EtOH-Blattextraktes von C. collinum. Im Agar-Well-Diffusionstest zeigte der Extrakt die größten Hemmhöfe gegen S. epidermidis, MRSA und S. aureus. Im Mikrodilutionstest wies der Extrakt durchschnittliche Hemmkonzentrationen von 275,0 µg/ml für S. epidermidis und 385,5 µg/ml für MRSA auf. Der Nachweis der antibakteriellen Aktivität liefert einen deutlichen Hinweis für den möglichen Nutzen der topischen Anwendung von Extrakten aus C.-collinum-Blättern in der traditionellen westafrikanischen Medizin. Die ethnomedizinische Verwendung bietet somit eine alternative Behandlungsoption für topische Infektionen durch Staphylococcus-Arten. From traditional healing to rational phytotherapy: phytochemical analyses and pre-clinical studies of antimicrobial activities from Combretum collinum Fresen. leaf extracts There are about 7000 different plant species in sub-Saharan Africa, which have a great potential to contribute to the nutrition and health care of the region's 1.2 billion inhabitants. Especially in Benin, a country in West Africa, medicinal plants are an important natural resource on which 80–99 % of the population depend to provide at least complementary, if not primary, basic health care. Leaves of Combretum collinum Fresen. (Combretaceae) are used in traditional West African medicine to treat bacterial infections and to promote wound healing. The present study focuses on the phytochemical characterization and analysis of the antimicrobial activity of a 50 % EtOH leaf extract of C. collinum. Analysis of the antimicrobial activity was performed with agar-well diffusion and microdilution tests. The phytochemical characterization was carried out with different chromatographic and spectroscopic methods (HPLC, LC-MS, flash chromatography, ¹H-NMR). The results confirmed myricetin-3-O-rhamnoside and myricetin-3-O-glucoside as the main polyphenolic compounds of the 50 % EtOH leaf extract of C. collinum. In the agar-well diffusion test, the extract demonstrated the largest inhibition sites against S. epidermidis, MRSA, and S. aureus. In the microdilution test, the extract showed inhibition concentrations of 275.0 μg/ml for S. epidermidis and 385.5 μg/ml for MRSA. The evidence of antibacterial activity provides a clear indication of the potential benefits of topical application of extracts of C. collinum leaves in traditional West African medicine. The ethnomedical use thus offers an alternative treatment option for topical infections caused by Staphylococcus species. Publication Date: 01 September 2020 (online) © Georg Thieme Verlag KG Stuttgart · New York