儲藏條件對海巴戟天葉萃取物之抗氧化活性與總酚類含量的影響

Effect of Storage Conditions on the Antioxidation Activity and Total Phenols of Extracts from Morinda citrifolia Leaf

本研究目的在探討海巴戟天葉之水、50%乙醇、95%乙醇及乙酸乙酯等萃取物，儲藏在不同的溫度（25-30℃、6-10℃與-30℃）和時間（最長儲藏時間為90天），對總多酚類含量與其抗氧化活性的影響。結果顯示各種海巴戟天葉萃取物，不論於何種儲藏溫度，儲藏90天後其總多酚類含量尚且穩定。各萃取液之總抗氧化能力隨時間的變化相似於總多酚類含量的變化，顯示各萃取液之總抗氧化能力與總多酚類含量有關。海巴戟天葉之水萃取物具有極佳的還原力（153.9±15.8 μmol/g抗壞血酸當量），並隨著儲藏時間的增加而提升，尤其儲存在25-30℃的條件下，其還原力上升的趨勢高於其他低溫儲藏條件；雖然海巴戟天葉之水萃取物在啟始時間也有較高的總多酚類含量(39.5±4.1mg/g)與總抗氧化能力（544.7±10.1 mg/g trolox 當量），但清除氫氧自由基能力不佳（萃取物濃度在100 μg/mL時，抑制百分比為6.6±2.1%）。95%乙醇萃取物在啟始時間，其總多酚類含量(54.3±1.3 mg/g)與清除氫氧自由基能力（萃取物濃度在100 μg/mL時，抑制百分比為46.5±1.8%）最高，若儲存在-30℃的條件下，90天內還能有效穩定其還原力、總抗氧化能力及清除氫氧自由基能力，此外其中抗氧化成分可能包含非多酚類物質，且高溫儲藏下並不穩定。

The purpose of the research was to investigate the effects of storage in different temperature (25-30℃, 6-10℃ and-30℃) and period (for 90 days) on total phenols content and antioxidation activity of aqueous, 50% ethanol, 95% ethanol and ethyl acetate extracts from noni leaf. The results showed that total phenols content of various extracts were stable in different storage condition for 90 days. The tendencies to antioxidation activity as a function of storage time in various extracts were the same as the changes for total phenols content. The tendencies indicated that antioxidation activity was relations to total phenols. Aqueous extract from noni leaf had better reducing power (153.9±15.8 mg/g ascorbic acid equivalent) and there was an increase in reducing power with increasing period in storage. Besides, the increase in reducing power stored at 25-30℃ was higher than at other low temperatures. Aqueous extract from noni leaf had higher total phenols (39.5±4.1 mg/g) and antioxidation activity (544.7±10.1 μmol/g trolox equivalent) at initial time, but had lowest the scavenging ability of hydroxyl radical (Inhibition percentage of 6.6±2.1% at 100 μg/mL in extract). 95% ethanolic extract from noni leaf had higher total phenols (54.3±1.3mg/g) and the scavenging ability of hydroxyl radical (Inhibition percentage of 46.5±1.8% at 100 μg/mL in extract) at initial time. Furthermore, trolox equivalent antioxidant capacity, reducing power and the scavenging ability of hydroxyl radical were relatively stable at -30℃ for 90days. This implied that non-phenolics compounds may contribute to the antioxidative activity of Noni's leaf extracts and these compounds are unstable at high temperature.