以密閉式藻類毒性試驗方法評估二級、三級炔丙基醇類之毒性與結構–活性關係之研究

Abstract

本研究以藻類（Pseudokirchneriella subcapitata）利用BOD瓶進行一密閉式系統之毒性試驗，使用溶氧變化量（△DO），藻細胞的數量變化（Final yield），以及以藻類細胞密度變化量計算所得的生長率（Growth rate）三個終點，評估二級以及三級炔丙基醇類之毒性，藉由Probit模式求出半致死濃度（50% Effect concentration，EC50）。以及利用物化參數logP以及Elumo值來評估這一類化學物質之QSAR。 本次實驗結果可發現三個參數中以Final yield的敏感度是最高的，而二級炔丙基醇類之毒性高低是和其炔基接的位置有一定的關聯性，三級炔丙基醇類之毒性則與疏水性的高低有關：疏水性越高其毒性越強。在與其他物種敏感度比較方面，敏感度的高低排列如下：BOD-FY > BOD-DO > Fathead minnow > BOD-GR >Tetrahymena Pyriformis。 在QSAR的分析方面，二級炔丙基醇當中去除三個炔基接在一的位置之化合物並且使用logP以及Elumo值對其毒性做迴歸分析，能得到不錯的迴歸效果（R2 = 0.852~0.926），然而三級炔丙基醇類，單純用logP值就能達到很好的效果了（R2 = 0.914~0.965）。此外，本研究以平均中斷值（cut-off value）作為選擇NOEC或EC10的客觀參考點，結果顯示NOEC比EC10較能提供生物更嚴謹的保護標準。

A closed-system algal toxicity test was applied to evaluate the toxicity of secondary and tertiary propargylic alcohols to Pseudokirchneriella subcapitata. The effects of propargylic alcohols were evaluated by three kinds of response endpoints, i.e., dissolved oxygen production, cell density, algal growth rate. Median effective concentraton (EC50) were estimated using the Probit model. The quantitative structure-activity relationships (QSARs) were established based on the 1-octanol/water partition coefficient (logP) and an electronic parameters-lowest unoccupied molecular orbit (Elumo). The result shows that the highest sensitivity is cell density between three end points, and the toxicity of secondary and tertiary propargylic alcohols is correlation to the position of alkynyl and hydrophobicity, respectively. Compare with sensitivity for other species, BOD-FY > BOD-DO > Fathead minnow > BOD-GR > Tetrahymena Pyriformis。 The QSAR about the secondary propargylic alcohols has a good fit (R2 = 0.852~0.926) with the logP and Elumo except three outliers that alkynyl attached to 1-position. The QSAR using logP for tertiary propargylic alcohols has a good fit (R2 = 0.914~0.965). Moreover, a cut-off value approach is proposed to determine whether NOEC or EC10 should be chosen for estimating low toxic effects. The results indicate that NOEC offers better protection to test organisms than EC10.