| Summary: | 碩士 === 國立臺灣大學 === 森林環境暨資源學研究所 === 106 === The depletion of ozone in the atmosphere has resulted in an increase in UV-B irradiation. A high UV-B dosage provokes damage to organism. Plants may attenuate the impact of UV-B irradiation through the accumulation of different types of phenolics produced. Most of these compounds are flavonoid, which can act as an effective UV-B screen. Moreover, some flavonoids may also eliminate free radicals which caused by UV-B radiation. This mechanism will make leaves to synthesis more active compounds, which can be used potentially. Cinnamomum osmophloeum is one of the indigenous trees in Taiwan. This tree contains aboundant kaempferol glycoside compounds in its leaves. These compounds were proved to have antioxidant activity and hypoglycemic effect. This study would irradiate C. osmophloeum leaves with UV-B in various conditions to test the variations of activity compound contents in the leaves.
First, we irradiate leaves with 4 h UV-B by different irradiation distances, and the changing ratio of the total flavonoid contents increase to the maximum 1.21 fold when irradiated at 30 cm (UV-B energy: 4.20 W m-2). We decided to use 30 cm as the irradiation distance for all other tests. Besides, we change 4 h UV-B irradiation to different order of different light irradiation. Only the test group of 2 h blue light + 2 h UV-B showed increased total flavonoid content ratio to 1.18 fold which is similar to the result when trees irradiated with UV-B for 4 h.
Furthermore, in order to know the maximum changing ratios of the active compounds per day, we treat C. osmophloeum leaves with 2, 4, 6 and 8 h irradiation. The changing ratios of the total flavonoid contents were better when irradiating with 4 or 8 h UV-B per day, with the best result when irradiating UV-B for 4 h. Furthermore, in investigating the changing ratio from the UV-B irradiation of the 5 major flavonoid compound, kaempferol-3-O-β-D-glucopyranosyl-(1→4)-α-L-rhamnopyranosyl -7-O-α-L-rhamnopyranoside (F1), kaempferol-3-O-β-D-apiofuranosyl-(1→2)-α-L -arabinofuranosyl-7-O-α-L-rhamnopyranoside (F2), kaempferitrin (F3), kaempferol-3-O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinofuranosyl-7-O-α-L -rhamnopyranoside (F4) and kaempferol-3-O-α-L-rhamnopyranoside (F5) in the water soluble fraction of C. osmophloeum leaves, the results showed that there were no significant differences between the changing ratios of compound F1-F5 from the irradiation with different hours of UV-B. As the result, we decided to treat leaves with 4 h UV-B irradiation as the continuous irradiation condition.
When the trees continuously irradiated UV-B for 4 h per day and lasted for 2, 4 and 8 d, the changing ratios of total flavonoid contents would significantly increase to 1.39 fold after irradiated UV-B for 4 d. But the result for irradiation for 4 d has no difference to that of irradiation UV-B for 8 d. The changing ratio of the total phenolic contents is significantly increased to 1.20 fold when irradiating UV-B for 4 d. Besides, when the tree irradiatind UV-B for 8 d, the changing ratio of total phenolic contents has significant increased to 1.37 fold. The 5 compounds, F1-F5, in the water fraction showed similar changing ratios to that of the total flavonoid contents. The changing ratios of compound F1, F2 and F3 would increase to 1.42 fold after irradiated UV-B for 4 d, but the result for irradiation for 4 d has no difference to that of 8 d.
As the result, we have concluded that to increase total flavonoid contents, total phenolic contents and the flavonol glycoside form water fraction, the most effective condition is to irradiate trees with UV-B at a 30 cm diatance for 4 h per day and last for 4 d. The total flavonoid contents would increase to 1.39 fold, the total phenolic contents would increase to 1.20 fold, the compound F1, F2 and F3 would increase to 1.42 fold when irradiating with this condition.
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