Isolation of 1',3'-dilinolenoyl'-2'-linoleoylglycerol with tyrosinase inhibitory activity from Flammulina velutipes

Enhanced oral bioavailability of a sterol-loaded microemulsion formulation of Flammulina velutipes, a potential antitumor drug

PURPOSE

To investigate the growth inhibition activity of Flammulina velutipes sterol (FVS) against certain human cancer cell lines (gastric SGC and colon LoVo) and to evaluate the optimum microemulsion prescription, as well as the pharmacokinetics of encapsulated FVS.

METHODS

Molecules present in the FVS isolate were identified by gas chromatography/mass spectrometry analysis. The cell viability of FVS was assessed with methyl thiazolyl tetrazolium (MTT) bioassay. Based on the solubility study, phase diagram and stability tests, the optimum prescription of F. velutipes sterol microemulsions (FVSMs) were determined, followed by FVSMs characterization, and its in vivo pharmacokinetic study in rats.

RESULTS

The chemical composition of FVS was mainly ergosterol (54.8%) and 22,23-dihydroergosterol (27.9%). After 72 hours of treatment, both the FVS (half-maximal inhibitory concentration [IC(50)] = 11.99 μg · mL(-1)) and the standard anticancer drug, 5-fluorouracil (IC(50) = 0.88 μg · mL(-1)) exhibited strong in vitro antiproliferative activity against SGC cells, with IC(50) > 30.0 μg · mL(-1); but the FVS performed poorly against LoVo cells (IC(50) > 40.0 μg · mL(-1)). The optimal FVSMs prescription consisted of 3.0% medium chain triglycerides, 5.0% ethanol, 21.0% Cremophor EL and 71.0% water (w/w) with associated solubility of FVS being 0.680 mg · mL(-1) as compared to free FVS (0.67 μg · mL(-1)). The relative oral bioavailability (area-under-the-curve values of ergosterol and 22,23-dihydroergosterol showed a 2.56-fold and 4.50-fold increase, respectively) of FVSMs (mean diameter ~ 22.9 nm) as against free FVS were greatly enhanced.

CONCLUSION

These results indicate that the FVS could be a potential candidate for the development of an anticancer drug and it is readily bioavailable via microemulsion formulations.

Identification of differentially expressed genes in Flammulina velutipes with anti-tyrosinase activity

It was previously shown that fruiting bodies of the mushroom, Flammulina velutipes, exert anti-tyrosinase activity by producing a triacylglycerol characterized as 1',3'-dilinolenoyl-2'-linoleoylglycerol (LnLLn). In this study, we provide evidence that the mycelia of F. velutipes grown on glucose, but not on glycerol, exhibit anti-tyrosinase activity. To identify genes possibly involved in the process of expressing anti-tyrosinase activity in F. velutipes, a reverse transcription-polymerase chain reaction (RT-PCR) method that involves annealing control primers (ACPs) was employed. Using 120 ACPs, a total of 84 differentially expressed genes (DEGs) in F. velutipes mycelia with anti-tyrosinase activity were cloned and sequenced. Basic Local Alignment Search Tool (BLAST) searches revealed that 72 of the genes have known sequence homology. Of these, three genes involved in the synthesis and modification of fatty acids were selected and further quantified by real-time RT-PCR. These genes involved in fatty acid-biosynthetic processes can be potential candidates for further studies related to the development of a new anti-browning agent.