Antioxidant activity, inhibition of nitric oxide (NO) overproduction, and antiproliferative effect of ethyl acetate extracts of maple sap and syrup from 30 producers were evaluated in regard to the period of harvest in three different regions of Québec, Canada. Oxygen radical absorbance capacity (ORAC) values of maple sap and syrup extracts are, respectively, 12 +/- 6 and 15 +/- 5 micromol of Trolox equivalents (TE)/mg. The antioxidant activity was also confirmed by a cell-based assay. The period of harvest has no statistically significant incidence on the antioxidant activity of both extracts. The antioxidant activity of pure maple syrup was also determined using the ORAC assay. Results indicate that the ORAC value of pure maple syrup (8 +/- 2 micromol of TE/mL) is lower than the ORAC value of blueberry juice (24 +/- 1 micromol of TE/mL) but comparable to the ORAC values of strawberry (10.7 +/- 0.4 micromol of TE/mL) and orange (10.8 +/- 0.5 micromol of TE/mL) juices. Maple sap and syrup extracts showed to significantly inhibit lipopolysaccharide-induced NO overproduction in RAW264.7 murine macrophages. Maple syrup extract was significantly more active than maple sap extract, suggesting that the transformation of maple sap into syrup increases NO inhibition activity. The highest NO inhibition induced by the maple syrup extracts was observed at the end of the season. Moreover, darker maple syrup was found to be more active than clear maple syrup, suggesting that some colored oxidized compounds could be responsible in part for the activity. Finally, maple syrup extracts (50% inhibitory concentration = 42 +/- 6 microg/mL) and pure maple syrup possess a selective in vitro antiproliferative activity against cancer cells.
"It has been demonstrated that transformation of maple sap in syrup improves NO inhibition activity. The heating process involved in the transformation of maple sap in syrup induces oxidation of the phenolics, suggesting its implication in the activity (Legault et al., 2010). Further research is needed to identify these compounds as they may contribute to the observed biological effects of maple syrup. "
[Show abstract][Hide abstract] ABSTRACT: The in vitro anti-inflammatory effects of a phenolic-enriched Canadian maple syrup ethyl acetate extract (MS-EtOAc) and 15 purified phenolic constituents were evaluated in a LPS-stimulated RAW 264.7 murine macrophage cell model. MS-EtOAc decreased nitric oxide (NO) and prostaglandin-E2 (PGE2) production at 10–100 μg/mL concentrations. The observed NO inhibition was a direct result of reduced nitric oxide synthase (iNOS) protein and gene expression through suppression of NF-κB transcriptional activation. In addition, MS-EtOAc upregulated cyclooxygenase-2 (COX-2) mRNA and protein expression. Among the 15 pure isolates, (E)-3,3′-dimethoxy-4,4′-dihydroxystilbene was most effective in decreasing both NO and PGE2 levels. However, 4-acetylcatechol, tyrosol, and protocatechuic acid only reduced PGE2 levels. Thus, the potential anti-inflammatory activity of MS-EtOAc can be attributed to its unique combination of compounds and not as a result of a single purified phenolic constituent alone. Future research on the purified phenolic compounds will be useful in understanding the overall in vitro anti-inflammatory effects of maple syrup.
"In fact, the relative levels of the most active isolates were higher in the grade D MS-BuOH extract. These results are in agreement with a previous report where darker grades of maple syrup were found to be more active than lighter grades (Legault et al., 2010). The antiproliferative activities exhibited by the maple syrup extracts were not due to cytotoxicity since the viability of the treatment cells was not significantly different from that of control cells. "
[Show abstract][Hide abstract] ABSTRACT: The antiproliferative effects of Canadian maple syrup (grades C and D) extracts and fifty-one purified phenolic constituents were evaluated against human tumourigenic (HT-29, HCT-116, and CaCo-2) and non-tumourigenic (CCD-18Co) colon cells. Overall, maple syrup ethyl acetate (MS-EtOAc), butanol (MS-BuOH), and methanol (MS-MeOH) extracts were more active against the tumourigenic versus non-tumourigenic colon cells. At equivalent phenolic levels, the antiproliferative activities of grade D>C maple syrup, and MS-BuOH>MS-MeOH>MS-EtOAc. Among the isolates, gallic acid, catechaldehyde, syringaldehyde, and catechol were most active and their higher levels in grade D MS-BuOH extract could account for the highest observed anticancer effects of that extract. Moreover, the maple syrup extracts did not induce apoptosis of the colon cancer cells but induced cell cycle arrest which was also associated with a decrease in cyclins A and D1 levels. These results suggest that phenolics may impart potential biological effects to maple syrup.
[Show abstract][Hide abstract] ABSTRACT: A solid phase extraction procedure was developed for the extraction of phenolic compounds from maple syrup. The list of targeted chemicals contains phenolic acids as well as aldehydes, flavanols and others such as coniferyl alcohol and 5-hydroxymethyl furfural. The procedure consists in passing a small quantity of maple syrup, 1 g diluted in 2 ml deionized water, through an Oasis HLB cartridge of 200 mg. The cleanest extracts were obtained by rinsing the cartridge load with formic acid 2 %/methanol (9:1). The analytes eluted with methanol were passed in an high-performance liquid chromatography (HPLC)-DAD system for analysis. The method performances show good recoveries; excluding gallic acid measured at 49 %, the chemical recoveries ranged from 81 to 119 %. Moreover, the method repeatability is less than 12 % (RSD) relative standard deviation for all chemicals except for epicatechin (20 %). The analysis method was applied for the determination of phenolic compounds in maple syrups from different color classes (Extra Light to Amber). Results show that concentrations of phenolic compounds vary among syrup classes and the greatest concentration was observed for the Amber syrups.
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