Resveratrol, a phenolic compound possessing vital biological activities such as anti-cancer, is present abundantly in grape skin, a waste produced during the processing of grape juice. The objectives of this study were to prepare resveratrol-gold nanoparticles and a resveratrol nanoemulsion from grape skin and study their inhibition effects on pancreatic cancer cells BxPC-3. The spherical-shaped citrate gold nanoparticles (GNPs) and resveratrol-gold nanoparticles (R-GNPs) were, respectively, prepared with a surface plasmon resonance peak at 528 and 538 nm, mean particle size of 20.8 and 11.9 nm, and zeta-potential at −32.7 and −66.7 mV, by controlling an appropriate concentration of citrate/resveratrol and gold chloride as well as stirring time and temperature. The resveratrol nanoemulsion, composed of soybean oil, Tween 80, and sucrose fatty acid ester in glycerol and water, possessed a high storage stability with a mean particle size of 14.1 nm, zeta-potential of −49.7 mV, and encapsulation efficiency of 95.5%. An antiproliferation study revealed that both R-GNPs and resveratrol nanoemulsion could effectively inhibit the growth of pancreatic cancer cells BxPC-3, with the latter showing a higher inhibition effect. Western blot analysis implied that both can down-regulate expressions of cyclin A, cyclin B, CDK1, and CDK2 and up-regulate expressions of p53 and p21, accompanied by enhancing cytochrome C expression, decreasing BcL-2 expression, increasing Bax expression, and leading to the elevation of caspase-8, caspase-9, and caspase-3 activities for cell apoptosis execution. Future research is needed to study the inhibition of pancreatic tumors in vivo by R-GNPs and resveratrol nanoemulsions.
Grape is a popular fruit crop that generates about one-fourth of total weight as pomace during winemaking and commercial juice production. However, a significant amount of resveratrol and related stilbenes is present in grape skin, and their effective isolation enables the production of functional foods. Herein, an improved analytical method for the determination of trans-resveratrol and related stilbenes in grape skin waste by QuEChERS method coupled with a high-performance liquid chromatograph-photodiode array detector-mass spectrometer was developed. By employing a Gemini C18 column and a mobile phase of acetic acid in water (pH 3.6) and acetonitrile, a total of five resveratrol and related stilbenes could be separated within 15 min with a flow rate of 0.8 mL min −1 and detection wavelength at 306 nm. The optimised QuEChERS conditions were 10 mL of acetonitrile, 1 mL of grape skin extract and 900 mg of magnesium sulphate plus 25 mg of primary secondary amine. Principal component analysis by two principal components (74.18%, 25.82%) could well describe the trans-resveratrol recovery at different QuE-ChERS conditions. A mean recovery, as well as coefficient of variation (CV, %) of repeatability and intermediate precision, ranged from 96.6% to 104.4%, 1.96% to 3.10% and 1.68% to 4.27%, respectively, conforming to the regulation set by Taiwan Food and Drug Administration. Quantitation revealed cispiceid to be present in largest amount (2.616 μg mL −1 ), followed by trans-piceid (1.027 μg mL −1 ), transresveratrol (0.967 μg mL −1 ), ε-viniferin (0.660 μg mL −1 ) and cis-resveratrol (0.183 μg mL −1 ) in grape skin extract, with their corresponding contents in dried grape skin being 4.185, 1.643, 1.539, 1.056 and 0.293 μg g −1 , respectively.
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