The investigation of inhibiting quorum sensing and methicillin-resistant Staphylococcus aureus biofilm formation from Liriodendron hybrid.

The quorum sensing (QS) of pathogens has been found to affect their biofilm forming ability, making it a potential target for anti-microbial therapy. The present research aimed to evaluate the anti-QS activities of different extracts and isolated phytochemicals from Liriodendron hybrid barks and their roles in the inhibition of the growth and biofilm formation of methicillin-resistant Staphylococcus aureus (MRSA). The assays on the inhibition of QS by the five extracts (n-hexane, dichloromethane, ethyl acetate, acetone, and methanol) and eight isolated compounds were carried out by using both the indicator strains Chromobacrerium violaceum CV026 and C. violaceum ATCC12472. The in vitro effects of the five extracts and eight isolated compounds on MRSA biofilm were also preliminarily evaluated using crystal violet micro titer plate assays. The results suggested that the dichloromethane extract showed anti-QS and MRSA biofilm inhibitory activities and the n-hexane extract possessed only MRSA biofilm inhibitory effect. The dichloromethane extract could serve as a source for developing bacterial intervention strategies targeting microbial QS system. All eight isolated compounds showed no anti-QS and biofilm formation inhibiting activities. So further researches are still being required to purify and identify the compounds possessing anti-QS and biofilm inhibitory effects from the dichloromethane and n-hexane extracts.

In vitro tumor cytotoxic activities of extracts from three Liriodendron plants.

The extracts prepared from Liriodendron tulipifera Linn., L. chinense (Hemsl.) Sarg., and their hybrid L. chinense x L. tulipifera, were investigated for their cytotoxic abilities in vitro against five human cancer cell lines: MDA-MB-231 and MCF-7 breast cancer cells, SGC-7901 gastric cancer cells, HuH-7 hepatocarcinoma cells, and HCT-15 colon carcinoma cells, and then measured their phenols and alkaloids contents. Of these plant extracts, some of them, especially the lower polar extracts from barks, exhibited potent cytotoxic effects on five tested tumor cell lines.