Abstract
Drypetes klainei Pierre ex Pax is used in Cameroon by Baka people in the wound healing process and for the treatment of burns. In a previous paper we demonstrated the ability of both water (WE) and defatted methanol (DME) extracts to accelerate scratch wound closure in fibroblast cultures, thus validating the traditional use of D. klainey stem bark in the treatment of skin lesions. In this work we carried out a bioassay-guided fractionation of the most active DME, which exhibited in vitro efficacy in accelerating wound healing process, in order to isolate and identify the compound/s responsible for the assessed biological activity. HPLC was used for the metabolite profiling of DME and fractions (analytical) and for the isolation of the bioactive compound (semi-preparative). MS analyses and NMR spectroscopy were used for identifying the isolated compound. The abilities of treatments in accelerating wound healing were studied on murine fibroblasts in terms of cell viability and cell migration (scratch wound-healing assay). The results obtained allowed to unambiguously identify the isolated bioactive compound as nigracin, a known phenolic glycoside firstly isolated and characterized from bark and leaves of Populus nigra in 1967. However, this is the first time that nigracin is identified in the Drypetes genus and that a wound healing activity is demonstrated for this molecule. Specifically, we demonstrated that nigracin significantly stimulates fibroblast growth and improves cell motility and wound closure of fibroblast monolayer in a dose-dependent manner, without any toxicity at the concentrations tested, and is still active at very low doses. This makes the molecule particularly attractive as a possible candidate for developing new therapeutic options for wound care.
Highlights
The traditional medicinal uses of 19 species of the genus Drypetes, distributed in Africa and Asia, and the isolation of about 150 compounds have been reported in a rather recent review (Wansi et al, 2016)
We previously demonstrated that both water (WE) and defatted methanol (DME) extracts from Drypetes klainei stem bark significantly improve the wound healing process in vitro, compared to untreated controls, and that the DME was active at lower concentrations, compared to the WE
fraction 1 (Fr1), fraction 2 (Fr2), and fraction 3 (Fr3) were tested for their ability to accelerate wound healing process in murine fibroblasts, in terms of cell viability and migration
Summary
The traditional medicinal uses of 19 species of the genus Drypetes, distributed in Africa and Asia, and the isolation of about 150 compounds have been reported in a rather recent review (Wansi et al, 2016). In a previous paper (Brusotti et al, 2015) we described the validation of the traditional use of Drypetes klainei, known among Baka people in Cameroon as a remedy in the wound healing process and in the treatment of burns. In order to complete the research on this plant, a bioassayguided fractionation of the most active defatted methanol extract (DME), which exhibited in vitro efficacy in accelerating wound healing process (Brusotti et al, 2015), was carried out, aiming to isolate and identify the compound/s responsible for the assessed biological activity. More recently nigracin was found in bark and twigs of Itoa orientalis (Chai et al, 2007), in leaves and twigs of Flacourtia indica (Sashidhara et al, 2013), in stems of Homalium ceylanicum (Liu et al, 2013) but, as far as we know, nigracin was never found before in the genus Drypetes
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