Polyphenolic Compounds Determination And Bioactivity EvaluationofDifferent Apple (Malus Pumila Mill.)Cultivars

To fully understand the variation of fruit quality among apple(Malus pumila Mill.) cultivars,35apple cultivars from National Germplasm Repository of Apple (Xingcheng, Liaoning province) were collected for the investigation of postharvest fruit quality, including color, firmness, total soluble solids (TSS), total phenolics, proanthocyanidins, and antioxidant capacity, etc. In addition, the composition and content of phenolics compounds in different cultivars were studied and their anti-tumor proliferation activity, cellular glucose consumption promotion activity and endothelial cells protection activity were evaluated. The main results are as follows:1. Significant differences were observed in fruit quality indices among35apple fruit cultivars. Among them,’Vista Bella’ had the lowest fruit firmness, while ’DanGuang’ had the highest fruit firmness. By using1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay and ferric reducing antioxidant power (FRAP) assay, the antioxidant activity of phenolics extracts from peel and pulp of35apple cultivars were evaluated. Results showed that antioxidant activities of apple fruit were significantly correlated with their total phenolics content and total proanthocyanidins content, respectively (R2>0.91). The antioxidant activity varied significantly among cultivars and tissues, and apple peel extracts showed relatively higher antioxidant activity than their pulp counterpart.’XBLYBD’ peel showed the highest total phenolic content (64.76mg CAE/g DW), while’Golden Delicious’peel showed the lowest (12.97mg CAE/g DW) in all the peel samples.’XBLYBD’ pulp showed the highest total phenolic content (58.11mg CAE/g DW), while ’XSJ’ pulp showed the lowest (2.39mg CAE/g DW) in all the pulp samples.2. Eleven phenolics compounds were identified from apple fruit, including cyanidin-3-galactoside, chlorogenic acid, proanthocyanidin Bl, proanthocyanidin B2, epicatechin, p-coumarylquinic acid, quercetin-3-rutinoside, quercetin-3-galactoside, quercetin-3-glucoside, quercetin-3-arabinoside and phlorizin. They can be classified into anthocyanins, phenolic acids, flavan-3-ols, flavonols and dihydrochalcones, respectively. Their content were significantly different among cultivars and tissues. For example, chlorogenic acid content in peel (0.02-2.76mg/g DW) was generally higher than that in pulp (0.07-4.39mg/g DW), cyanidin-3-galactoside and flavonol glycosides can be detected only in the peel. The contents of phenolic acids and flavan-3-ols showed significant correlation with the antioxidant activity, indicating that they may play important role in antioxidant activity of apple extract.3. The in vitro anti-tumor proliferation activity of apple extracts were evaluated by HepG2liver cancer cell line. The results showed that, apple extracts significantly inhibited HepG2cell proliferation, with the inhibition activity varied significantly between cultivars. For example,’XBLYBD’pulp extract showed the lowest IC50values (5.02μg/ml), while ’ZSX’ pulp extract showed the highest IC50values (21.05(μg/ml). The anti-tumor proliferation activity was correlated with the content of epicatechin in peel (R2=0.643) and proanthocyanidin B2in peel (R2=0.655). Such results indicated that these compounds in apple extracts may play important roles in inhibiting tumor cell proliferation.4. In addition, the HUVEC protection activity and cellular glucose consumption promotion activity of the apple peel and pulp extracts were evaluated. Results showed that ’JS’ pulp extract,’XBLYBD’ peel and pulp extracts showed protective effects on HUVEC injury caused by H2O2.’CX’ and ’JX’peel extracts significantly increased cell viability (56.39%and53.42%, respectively), compared to33.63%of control.’HFS’peel extract,’XBLYBD’ peel and pulp extracts as well as ’Jinshuai’ peel extract significantly increased glucose consumption in HepG2cells, all in dose-dependant manners. An increase of41.3%in the cellular glucose consumption was observed by the’HFS’peel extract treatment.Overall, the present evaluated the phenolic compounds and different bioactivities among35apple cultivars. Research findings may provide scientific basis for further nutritional investigation of the apple resources, which is important for the development of apple industry in China.