Short Report

Antibacterial furofuran lignans from Canary Islands propolis

A new rearranged lignan, asasiebolin (1), was isolated from a kind of traditional Chinese medicine Asarum sieboldii, together with two known lignans, L-sesamin and L-asarinin. Asasiebolin (1) contained a benzo[d][1,3]dioxole-5-carboxyl moiety linked to a hydroxymethyl at C-3 of the tetrahydrofuran core, which might be rearranged after a cleavage from C-4. The structure with relative configuration was elucidated by in-depth spectral methods.

Propolis is a resinous mixture that honey bees collect from the tree buds, sap flows, or other botanical sources. The chemical composition of propolis varies and depends on the geographical area, time of collection, seasonality, illumination, altitude, and food availability during propolis exploitation. The goal of this review is to discuss important concepts including mechanisms of action and therapeutic activities of propolis. The PubMed, ScienceDirect, and Cochrane Library databases were searched for the literature published from January the 1st 2000 to October the 1st 2017. Sixteen animals and three clinical studies were included. A quantitative and qualitative review was performed on the clinical trials and the animal studies were comprehensively overviewed. In this study, the clinical trials have been combined and the results were provided as meta-analysis. Propolis is a non-toxic natural product; however some cases of allergy and contact dermatitis to this compound have been described mainly among beekeepers. An important factor in impaired wound healing is biofilm formation; propolis as an anti-microbial agent can reduce biofilm generation and result in accelerated healing processes. Most of the in vivo studies on various wound models suggested the beneficial roles of propolis on experimental wound healing and this has also been approved in the clinical trial studies. However, there is a lack of information concerning, dose, side effects and clinical effectiveness of propolis on wounds. As the effectiveness of propolis between different products is variable, more characterizations should be done and future investigations comparing different propolis based products and characterization of their specific roles on different models of wounds are highly appreciated.

Phytochemical study on the roots of Asarum sieboldii resulted in the isolation of one new compound, (1R,2S,5R,6R)-5′-O-methylpluviatilol (1) and 12 known compounds (2–13). Their structures were determined by extensive spectroscopic methods, including 1D and 2D NMR, and MS spectra. The absolute configuration of compound 1 was established using CD spectrum. Compounds 4, 5, and 12/13 significantly inhibited TNFα-induced NF-κB transcriptional activity in HepG2 cells in a dose-dependent manner, with IC₅₀ values ranging from 6.4 to 9.4 μM. Furthermore, the transcriptional inhibitory function of these compounds was confirmed based on decreases in COX-2 and iNOS gene expression in HepG2 cells. Compounds 1–3, 6, 7, 10, and 11 significantly activated the transcriptional activity of PPARs in a dose-dependent manner, with EC₅₀ values ranging from 1.7 to 20.9 μM. Compounds 7, 10, and 11 exhibited significant dose-dependent PPARα transactivational activity, with EC₅₀ values of 19.5, 15.7, and 4.0 μM, respectively. Compounds 1, 6, 7, 10, and 11 activated PPARγ transcriptional activity, with EC₅₀ values ranging from 3.6 to 22.6 μM, whereas compounds 10 and 11 significantly increased PPARβ(δ) transactivational activity, with EC₅₀ values of 22.6 and 4.9 μM, respectively. These results provide a scientific support for the use of the roots of A. sieboldii and warrant further studies to develop new agents for the prevention and treatment of the inflammatory and metabolic diseases.