| Summary: | 碩士 === 國立臺灣大學 === 食品科技研究所 === 97 === Epidemiological studies have shown that dietary flavonoids may contribute to the prevention of oxidative damage in our body. Among different flavonoids, proanthocyanidins have received quite significant interest due to their observed health benefits. Previous study in our laboratory indicated that the water and methanol extracts of longan (Dimocarpus longan Lour.) flower had good antioxidative activity, and proanthocyanidin A2 (PA2) and (-)-epicatechin (EC) were found to be the major active compounds.
PA2 is a very unstable compound, it could easily be transformed to its isomers epicatechin-(4β→8;2β→O→7)-ent-catechin (PA4) and epicatechin- (4β→6;2β→O→7)- ent-catechin (PA5) in cell culture medium. PA2 and EC are present together in longan flower, so the objective of this study was to use the 4 pure compounds PA2, EC, PA4 and PA5 and also 4 compounds mixtures with different molar or weight ratios of PA2 and EC (2:1), (1:1), (1:2) and nature existence condition (1:3.3), to test their bioavailability, anti-inflammatory and anti-oxidant effects.
The Caco-2 cells model has been used to test the bioavailability. Caco-2 cells are derived from human adenocarcinoma and will differentiate into polarized enterocyte-like monolayers, acting similarly to human intestinal epithelial cells. Caco-2 cell monolayer system has provided a useful model to evaluate intestinal transepithelial transport and accumulation of pure phytochemicals. Results of this study showed that PA2 could be absorbed and transported to basolateral side with the apparent permeability coefficient (Papp) of 4.72 ± 0.42×10-6 cm/s but EC could not be transported to basolateral side. On the other hand, PA4 can be absorbed and transport to basolateral side with the Papp = 11.45 ± 5.02×10-6 cm/s which was even higher than PA2, it may be due to the presence of catechin in the lower unit of the molecule. Nevertheless, PA5 (Papp = 2.51±0.21×10-6cm/s) did not possess good permeability as PA4, the reason needs further investigation. As for the mixtures groups, it was found that the permeability of PA2 was interfered by the presence of EC and EC still could not be absorbed by Caco-2 cell.
Inhibition of LPS-induced NO production in RAW264.7 cell was used as anti-inflammatory assay model. PA2 showed good ability in inhibiting NO formation but PA2 isomers did not show as good effects. Compared to PA2, EC was found to be less effective. As for the mixtures groups, the anti-inflammatory effect was better when EC was in lower ratio in the mixture.
In the chemical based in vitro antioxidant assays (DPPH, ORAC) EC had better antioxidant activity than PA2. However, in the cell based antioxidant assay (CAA), the effect of PA2 was far better than EC. The mixture group also has this similarity: when the EC was present more in the ratio, the chemical based in vitro antioxidant effect was better but the cell based antioxidant effect was worse. This may be because EC can not be absorbed by cells.
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