Study On Phenolic Compounds And Their Antioxidant Activities From Peach Fruit

Peach fruit are an important part of human diet due to their nutritional value. In addition to vitamin C and E, peach fruit contain large amount of phenolic compounds. Recently, many researches have reported the beneficial effects of these phenolic compounds to human health, such as antioxidant, anticancer, anti-inflammatory and prevention of cardiovascular diseases. In this paper, the antioxidant potentials of five different peach cultivars and the relationship with the antioxidant bioactive compounds of the peach fruit was investigated. The antioxidant properties of the peach fruit extract was evaluated for their potential antioxidant capacity by several assays and tested for their antioxidant bioactive compounds. We also discuss the impacts of peach tissues, mature stages, different postharvest treatments and storage conditions on these bioactive compounds and antioxidant activities. The main results were as follows:The cellulose mediated extraction of phenolic compounds from peach fruit was optimized by single factors trial and Box-Behnken experiment design, considering the effects of four parameters such as addition of cellulose, temperature, enzymatic duration and pH value. The results showed the best combination for the extraction were:2.0% (addition of cellulose),43℃, pH 4.0 and 30 min (enzymatic duration), respectively. Under the optimized conditions, the experimental value of yield is 45.49 GAE/100 mg FW, which was agreed well with the estimated value of 0.8% with relative error.Purification of phenolic crude extract from peach fruit on macroporous resin was studied. Through static adsorption and desorption tests, D101 resin was chosen for the separation of phenolics due to its higher adsorption and desorption capacity. Then, dynamic adsorption and desorption experiment was carried out on a D101 resin packed column to obtain optimal separation parameters. The results revealed that the largest adsorption capacity of D101 was achieved when initial phenolic concentration was 10 mg/mL (pH 4.5), feed flow was 2 mL/min and feed volume was 10.9 bed volume (BV). The saturated resin with feed volume 25 BV was first washed using water to remove impurities such as sugar and proteins, and then eluted with 200 mL 70% aqueous ethanol at flow rate of 1 mL/min. The desorption ration of phenolics from resin was up to 91.3%, and the purity of phenolic in crude extracts was increased from 31.2% to 85.7%. The yield and recovery of phenolics was 0.62% and 78.5% respectively.This study determined the total phenolic content, individual phenolic composition and evaluated antioxidant properties, separately for pulp and peel. The antioxidant activities were evaluated by means of several in vitro methods, such as the β-carotene/linoleate test, ABTS·+ and DPPH radical scavenging capacity and iron reducing power. The results showed that the predominant phenolic compounds in the five peach cultivars was found to be chlorogenic acid, followed by neo-chlorogenic acid, (+)-catechin, quercetin-3-rutinoside and protocatechuic acid. There was significant differences in phenolic contents among all analyzed peach cultivars. In addition, peach peels had a higher phenolic content than pulp tissue. We also found a significant positive correlation between total phenlic contents and antioxidant activities based on different assays.The changes of physiochemicals associated with fruit quality, antioxidant component and antioxidant properties during the last month on-tree ripening were investigated. The correlation between ascorbic acid or phenlics content and the antioxidant properties was determined. The results showed that the ascorbic acid and phenolic content as well as antioxidant activities decreased dramatically over the ripening period. Based on correlation analysis, we found that the antioxidant activity may highly affected by hydroxycinnamates (chlorogenic and neo-chlorogenic acid) and flavan-3-ols ((+)-catechin) contents.This study investigated the postharvest characters, phenolic compounds and total antioxidant activities in response to 1-methylcyclopropene (1-MCP) during the ripening process of peach (cv. Yuhualu) fruit. The results showed that 1-MCP treatment best retained fruit quality. Additionally, ethylene production and respiration rate were delayed. 1-MCP significantly reduced levels of chlorogenic acid and neo-chlorogenic acid, but enhanced levels of (+)-catechin and quercetin-3-rutinoside in the peach fruit. Compared with the control peach, the application of 1-MCP treatment had no significant effect on the protocatechin acid. Moreover, treatment with 1-MCP effectively postponed the onset of peak values of phenolic compounds positively identified in the peach fruit as well as antioxidant activities.Effects of storage temperature on fruit quality and nutritional value of peach cultivar (cv. Yuhualu) were investigated. Peaches were stored at 0℃,2℃,4℃ and 6℃ for 30 or 50 days. Browning index and other quality parameters were taken as reference index for evaluate the effect of different storage temperatures on quality of peach. Meanwhile, the changes of phenolic compounds and antioxidant activities were monitored during the storage time. Our results indicated that 0℃ and 2℃ can keep a longer storage duration, effectively delay and reduce the occurrence of chilling injury, significantly inhibit ethylene production and respiration rate as well as maintain a higher fruit quality. However, peach fruit stored at 0 and 2℃ showed lower L-ascorbic acid, phenolic compounds and antioxidant capacities than those stored at 4 and 6℃. Therefore, for immediate consumption or short holding period, keeping peaches at warm temperature (e.g.4 or 6℃) is desirable for obtaining high antioxidants. However, if extending the storage life of the fruit is the goal, keeping the fruit as cold as possible without freezing (e.g.0℃) is recommended.Effects of fumigation with 5 μL L-1 1-methylcyclopropene (1-MCP), intermittent warming (IW) and a combination of 1-MCP and IW (1-MCP plus IW) on chilling injury, fruit quality, phenolic compounds and total antioxidant properties as well as relative enzyme activities were evaluated in peach (cv. Yuhualu) fruit. 1-MCP could counteract the side effect of IW, and 1-MCP+IW significantly prevented the chilling injury and obviously maintained the fruit quality of’Yuhualu’ peach. Additionally, treatment with 1-MCP alone or combined with IW effectively delayed and elevated the accumulation of phenolic compounds and TAA of peach fruit during cold storage and subsequent shelf life. Peaches treated with 1-MCP+IW had significantly higher levels of phenolic compounds, antioxidant capacities and relative enzyme activities than other treatments.