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Aims and Background: In this study, the efficacy of silicon (Si) was determined in order to increase the pool of phenols and antioxidant activity in plum (Prunus salicina Shablon) fruits and, thereby, enhance postharvest plum fruit quality.
Materials and methods: The fruits were randomly divided in two groups so that Si-treated group immersed for thirty minutes in solutions of 5 g/l Si and were air-dried at room temperature. The activities of catalase (CAT) and superoxide dismutase (SOD) were determined.
Results: Postharvest silicon application had no effect on CAT activity in contrast, weight loss, total phenolics concentration, lipid peroxidation as well as phenylalanine ammonia-lyase (PAL) and SOD activity responded positively to the Si treatment. Silicon application raised phenylalanine ammonia-lyase activity and total phenol concentrations led to increase the fruit’s ability to better withstand stressful cold impacts. In addition, Si considerably reduced the rise in malondialdehyde (MDA) content during storage, obviously because of an efficient scavenging following significant enhancement of SOD activity.
Conclusion: Postharvest Si application raised antioxodant activity and total phenolic, reduced malondialdehyde content and lipid peroxidation, and led to increase the fruit’s ability to better withstand stressful cold impacts. These results suggest that Si application may be recommended for increasing storage life and maintaining their quality.

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Aim and Background: Plant bioactive substances are a valuable source of various medicines that play an important role in human health. Increasing resistance to different antibiotics has increased the importance of using plant extracts as they have potential sources of antioxidants. Antioxidant compounds of plant origin can protect the body from damage caused by oxidative stress. Recently, the use of natural antioxidants derived from medicinal plants has had medicinal and medical applications. Comparison of the antioxidant activity and total phenolic compounds of Thuja orientalis leaf extracts isolated from the three heights (1, 2, and 3 meters) of Noshahr and Tehran.

Material and Methods: In this experimental study, the leaves of Thuja orientalis were collected in spring from Tehran and Noshahr cities at three heights (1, 2, and 3 meters). Subsequently, the methanolic and aqueous extracts were prepared and their antioxidant activities were evaluated using DPPH and FRAP methods. In addition, the content of the phenolic extract of the extracts was measured by the Folin-Succtile method.
Results: The results of this study showed that both aqueous and the methanolic extracts of T. orientalis exhibited significant total antioxidant activities at a height of 3 meteres. The methanolic extract of T. orientalis collected from Tehran and Noshahr in height of 2 meters showed the howest amounts of antioxidant activity. Moreover, the highest and lowest amounts of total phenolic compounds were belonged to aqueous and the methanolic extracts of T. orientalis collected from Noshahr.  
Conclusion: The results of this study showed that the leaf extract of the C. orientalis can be used as an promising source for the synthesis of antioxidant compounds.