عنوان مقاله [English]
Introduction: Citrus is in the first rank in the world with respect to production among fruits. They are grown commercially in more than 50 countries around the world. Several factors such as rootstock, nutrition and irrigation regimes, cultivation design and etc. may affect the promotion of quality and quantity of fruits. Lemon fruits are among the most valuable functional diets shown to lower oxidative-related disease risks, particularly cardiovascular disease. A well-documented characteristic of these fruits is the accumulation of high amounts of glycoside flavonones, named hesperidin in the fruits. Several recent studies have demonstrated that the cytoprotective action of citrus fruits is enhanced by the presence of antioxidants including vitamin C, phenolics, carotenoids and flavonoids. Hesperidin and its metabolites significantly have been found to lower the total cholesterol and triglyceride concentrations in plasma. Hesperidin acts as a chemopreventive agent against colon carcinogenesis induced by azoxymethane. Lemons are one of the citrus species having many medicinal effects owing to their secondary metabolites. Flavonoids are a part of aromatic polyphenols having different biological actions such as antioxidant activity, anti-cancer, anti-sensation and etc. Hesperidin is one of the abundant secondary metabolites belonging to flavonoids in citrus, which is effective in treating many diseases.
Materials and Methods: In order to investigate the effect of lemon fruits (Citrus lemon cv. Cluster, C. lemon cv. Lisbon and C. lemon cv. Eureka) tissue type and harvesting time on the flavonoids hesperidin content, this experiment was carried out. Thus, this research was conducted in a factorial arrangement on the basis of completely randomized design with three factors: tissue type (Flavedo, Albedo and Flesh), harvesting time (45, 75, 105 and 135 days after full bloom) and three lemon cultivars (Cluster, Lisbon and Eureka) with three replications. Studied trees in Kotra Research Station were planted for research aims and were 20-year grafted on sour orange rootstocks. For selection of trees, the same height, crown, and other morphological attributes were considered. As the fruit quality may be differ in different parts of crown, fruits were harvested from different geographical orientations of crown. Samples were gathered after full bloom at the 30-day intervals. The measured parameters were included fruit weight, diameter, peel thickness, dry matter and hesperidin flavonoid in extraction of various fruit tissues. Extraction was conducted by methanol and hesperidin content recorded by High Performance Liquid Choromatography (HPLC). Chemicals and reagents used in this study were high quality grade and acquired from Sigma-Aldrich
Results and Discussion: Results showed that the fruit harvesting time significantly affected on fruit diameter, peel thickness, dry matter and also hesperidin content of tissue extraction. Fruit diameter variation was related to the fruit weight. The highest fruit weight attained in cultivars Lisbon and Eureka (88.39 g and 84.72 g, respectively) at the fourth harvesting time (135 days after full bloom) and the minimum, in sour lemon cv. Cluster (4.16 g) at the first harvesting time (45 days after full bloom). The maximum of fruit diameter was recorded in cultivar Lisbon (54.81 mm) at the fourth harvesting time and the minimum diameter in cultivar Eureka (20.75 mm) at the first harvesting time. Fruit peel thickness at the first harvesting stage increased and then decreased. Cluster sour lemon cultivar possessed the highest peel thickness (7.16 mm) and the Eureka cultivar had the minimum (4.66 mm). Percentage of dry matter increased at the first harvesting stage and then decreased. The maximum percentage of dry matter was recorded in cluster sour lemon cultivar (22.83%) and minimum in Lisbon lemon cultivar (11.36%). The highest amount of hesperidin was observed in Lisbon cultivar (1606.93 ppm). These amounts decreased afterward until fruit harvesting time. The highest hesperidin content was produced in albedo tissue. Lisbon lemon in the hesperidin was better than the other two cultivars. It is concluded that the most suitable time of mature fruits harvesting is 45 days after full bloom. At this time the fruit diameter of lemon cv. Eureka, Lisbon and Cluster were 20.7, 22.8 and 25.8 mm; respectively. Hesperidin flavonoid was produced in albedo tissue in all cultivars. Therefor; fruit albedo tissue can be regarded as the best tissue for extracting hesperidin. Hesperidin was severely affected by harvesting time, tissue and cultivar. Hesperidin was achieved in the most amounts at the first harvesting stage in Lisbon lemon compared to all studied cultivars. As the fresh consumption of Eureka, Lisbon and specially Cluster lemon is few, thus preparing programs to extract flavonoid and use this cultivar in food industries is suggested.