田間氮磷肥施用量對黃荊產量、精油含量及組成分、 多酚含量與抗氧化活性的影響研究

Abstract

黃荊 (Vitex negundo Linn) 為可食藥用香草植物，主要分布於亞洲及非洲熱帶地區，其具有廣泛的藥理活性如抗蟲、抗菌及抗發炎等。依據《中華藥典》記載，黃荊具有散風祛痰，止咳平喘功能，主要用於治療感冒咳嗽、哮喘及胃痛等病症。黃荊精油的主要活性成分為石竹烯 (β-caryophyllene) 及佛術烯 (eremophilene)，其中石竹烯具有抗發炎、抗焦慮及抗憂鬱等功效，而佛術烯則具有抗菌、抗癌及免疫調節等活性。雖然目前已有不少有關黃荊的活性研究報告，但是黃荊栽培技術及肥培管理的相關研究仍非常缺乏，因此本研究的目的為探討施用氮肥及磷肥對黃荊的生長、精油產量及組成分、多酚類含量與抗氧化活性的影響。本研究以田間方式進行，試驗採用隨機完全區集設計 (RCBD)，依據肥料施用量共分為氮肥控制組 (無施用肥料)、磷肥控制組 (無施用肥料)、三種量之氮肥處理組 (分別為50、100及200 kg-N ha^(-1)) 及三種量之磷肥處理組 (分別為50、100及200 kg-P ha^(-1))，種植180天後採收黃荊地上部，並分析土壤及植體樣品。結果顯示，200 kg-P ha^(-1)磷肥處理組之生質量及精油產量為最高，且精油中之化學成分種類為最多 (45種)、其次為100 kg-P ha^(-1)磷肥處理組 (42種)，200 kg-N ha^(-1) 氮肥處理組及50 kg-P ha^(-1)磷肥處理組之精油則含有40種化學成分。此外，200 kg-P ha^(-1)磷肥處理組也具有最高佛術烯的含量。各處理之間的總酚類及總黃酮類濃度結果並無顯著差異，但隨著氮肥及磷肥施用量增加，氮肥及磷肥處理組之總酚類則有先減少而後增加的現象，而磷肥處理組之總黃酮類含量也有相同的趨勢，推測此結果為氮磷肥施用量比例之差異，影響黃荊對磷的利用，造成總酚類及總黃酮類濃度的改變。抗氧化活性結果顯示，各處理組地上部萃取物及精油之DPPH（1,1-diphenyl-2-picrylhydrazyl）自由基清除力並無顯著差異；隨著氮肥及磷肥施用量增加，氮肥及磷肥處理組地上部萃取物的鐵離子還原力(Ferric reducing antioxidant power；FRAP) 結果則有先減少而後增加的趨勢且與總酚類及總黃酮類濃度結果相似，因此推論黃荊地上部的抗氧化能力與總酚類及總黃酮類濃度有關；然而，黃荊精油之FRAP鐵離子還原力結果顯示，各處理組間並沒有顯著差異，表示不同氮磷肥施用量對黃荊精油之FRAP鐵離子還原力的影響不顯著。本研究說明施用200 kg-P ha^(-1)之磷肥可有效促進黃荊之生質量與精油產量，以及提升黃荊主要活性成分的含量。

Vitex negundo Linn is an edible aromatic medicinal plant, which is distributed throughout tropical Asia and Africa. The shoots of V. negundo possess various medicinal properties, such as pesticidal, anti-fungal, anti-bacterial and anti-inflammatory activity. According to the Chinese Pharmacopoeia, V. negundo is used as a medicinal plant for the treatment of cough, flu, asthma and stomachache. The main bioactive compounds present in V. negundo essential oil are β-caryophyllene and eremophilene. β-caryophyllene possesses anti-inflammatory, anti-depression and anti-anxiety activities, eremophilene possesses anti-microbial, anti-cancer and immunomodulatory properties. To date, although many studies have reported on the bioactivities of V. negundo, information on the cultivation and fertilizer management of V. negundo still remains limited. Therefore, the objective of this study was to evaluate the effects of nitrogen and phosphorus fertilization rates on the biomass, essential oil yield and composition, polyphenol contents and antioxidant activities in V. negundo. This study was conducted under field conditions, eight treatments namely nitrogen control (no fertilizer；NCK), phosphorus control (no fertilizer；PCK), three different rates of nitrogen (50, 100, 200 kg-N ha^(-1)) and three different rates of phosphorus (50, 100, 200 kg-P ha^(-1)). After 180 days of cultivation, soil sample and shoots of V. negundo were collected for chemical analysis. The results showed that at 200 kg-P ha^(-1) phosphorus, V. negundo had the highest biomass and essential oil yield. The essential oil compositions of V. negundo showed that 200 kg-P ha^(-1) treatment had the highest number of volatile components (45 compounds), followed by 42 compounds in 100 kg-P ha^(-1) treatment, 40 compounds in 200 kg-N ha^(-1) treatment and 50 kg-P ha^(-1) treatment. In addition, 200 kg-P ha^(-1) treatment also showed the highest contents of eremophilene (23.44%) content. Total phenolic and total flavonoid contents in shoots of different fertilizer treatments were not significantly different. However, with the increasing rates of nitrogen and phosphorus fertilization, the contents of total phenols in shoots of different nitrogen and phosphorus treatments appear to decrease, and then increased. Similar result also found in the contents of total flavonoid in shoots of different phosphorus treatments. The changes of total phenolic and total flavonoid contents in shoots could be due to the different nitrogen and phosphorus fertilization rates. Antioxidant activity studies of V. negundo shoot extracts and essential oils showed that there were no significantly difference in DPPH（1,1-diphenyl-2-picrylhydrazyl）radical scavenging activity. Antioxidant activity studies of V. negundo essential oils also showed that there were no significantly difference in the FRAP (Ferric reducing antioxidant power) assay. However, the FRAP assay values of the V. negundo shoot extracts were found to decrease, and then increased with increasing nitrogen and phosphorus fertilization rates, its values were similar to the total phenolic and total flavonoid contents, suggesting that the amount of polyphenols might contribute to the antioxidant capacity of V. negundo shoots. In conclusion, this study indicates that 200 kg-P ha^(-1) phosphorus fertilization rates has a positive effect on the biomass, essential oil yield and bioactive compounds of V. negundo.