| Summary: | 碩士 === 國立屏東科技大學 === 農園生產系所 === 106 === Guava is one of the important economic fruit trees in Taiwan. In addition to its fruits, its leaves are rich in antioxidant components and have the potential for the prevention of degenerative diseases. The aim of the present study was to understand the effects of drying temperature and duration on the total phenolic content and antioxidant capacity of guava leaves at young and mature stages. The variations of total phenolic content, antioxidant capacity and α-amylase inhibitory rate among genotypes were also investigated. In total, 36 genotypes were evaluated including six cultivars, five introduced or collected cultivars (line), 23 breeding lines and two related species. The results showed that drying young leaves at 40°C for 48 hours generally had the highest total phenolic content and antioxidant capacity among treatments. However, no significant difference was found between treatments at 40°C and at 50°C for 12 hours. When drying leaves at 50°C for 12 hours, it was found that there were significant variations in total phenolic content, FRAP, DPPH radical-scavenging power and α-amylase inhibitory activity among genotypes. Young leaves were better than mature leaves in terms of total phenolic content and antioxidant capacity. The total phenolic content, FRAP, DPPH scavenging power and α-amylase inhibition rate of the young leaves of the genotypes ranged from 197.89 to 94.52 mg GAE/g, 34.42 to 9.78 g Vitamin C/g, 45.62 to 13.52 g Trolox/g and 79.0% to 13.7%, respectively. Regardless of the leaf ages, total phenolic content is highly significantly correlated with both FRAP and DPPH scavenging power. Genotypes show better quality than the commonly grown cultivars in total phenolic content, antioxidant capacity and α-amylase inhibition rate have been selected. They can be used for further breeding or healthy product development.
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