| Summary: | 碩士 === 國立屏東科技大學 === 熱帶農業暨國際合作系 === 101 === Tetranychus kanzawa Kishida cause serious damage to crops due to their short lifecycle, high reproduction, and induced pesticides resistance. However, the traditional agrochemicals can cause serious environmental pollution. Therefore, it is necessary to develop environmental-friendly plant-source pesticides as part of the integrated pest management (IPM). Oil-tea seed dreg is the by-product after oil production from the seeds of Camellia oleifera Abel. The objective of this study was to evaluate the potential of oil-tea seed dreg as an alternative natural pesticide against T. kanzawa. The crude extracts (Aqueous, 50% EtOH, 95% EtOH, and acetone) from oil-tea seed dreg were used in the antimite activity test against T. kanzawa. The crude aqueous extract showed slow-toxicity and the highest lethal effect against female adult among crude extracts. The 50% lethal concentration (LC50) values of after 72 h, were 9.92 mg/mL for aqueous extrect, followed by 95% EtOH extract (20.35 ± 1.93 mg/mL), 50% EtOH extract (24.19 ± 3.35 mg/mL) and
acetone extract (25.85 ± 6.65 mg/mL). The aqueous extract at 14.26 mg/mL caused low mortality of the female adult mites, however, their feeding ability was lost due to epilepsy. At high concentration, swelling and softening of the bodies were evident. The aqueous extract was further partitioned with n-Butanol, producing n-Butanol and aqueous fractions. The aqueous fraction showed higher mortality than that of n-Butanol fraction against T. kansawai suggesting that its bioactive compounds were of high polarity. The LC50 values of n-Butanol fraction and aqueous fraction after 72 h was 12.44 mg/mL and 65.02 mg/mL, respectively. Furthermore, both fractions were separated by column chromatography and grouped into 5 sub-fractions by thin layer chromatography (TLC) in order to find out which sub-fraction containing active compounds. The mortality (70.02%) of T. kansawai treated with 15 mg/mL of A4 sub-fraction was significantly higher than other sub-fractions at the same concentration. However, the lethal activity was reduced after the fractions were separated. Therefore, it can be implied that a synergistic or additive effect of compounds existed in oil-tea seed dreg. As a result, the bioactive components were analyzed by LC-ESI-MS after HPLC isolation and purification. The molecular weights of components were similar with several tea saponins. In oxidative stress experiment, superoxide dismutase (SOD) and peroxidase (POD) were increased after 24 h then inhibited after 48 h. Moreover, after 72 h, the inhibition of SOD and POD were 100% and 89.68 ± 4.28%, respectively. On the contrary, after 24 h after treatment, inhibition of catalase (CAT) was 27.29 ± 7.24%; however, 72 h after treatment, enzyme activity became active (-25.36 ± 12.04%). As a result, the extract of oil-tea seed dreg performed effective antimite activity against T. kanzawa, and the induced oxidative stress may contribute to it’s effect.
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