物化性質影響 triterpenoids 在兔子眼角膜穿透作用 之探討
藥物的吸收在藥劑上扮演著重要的角色，而細胞膜的屏障一直是影響藥物吸收的重要因素
，藉由 14C-estradiol 和 14C-mannitol 的穿透實驗來評估藥物的吸收能力是目前藥劑上研 究促進劑干擾細胞膜的方式之一。本研究主要探討齊墩果酸 (oleanolic acid ; OA) 、熊 果酸 (ursolic acid ; UA) 和白樺酸 (betulinic acid ; BA) 這些 triterpenoids 的促進劑
對藥物在兔子眼角膜上穿透的影響。利用 Diffusion cells 的裝置來進行兔子眼角膜之體 外穿透實驗，並利用一系列不同的： (1) 溫度 (2) 帶電性 (3) 粒徑大小 (4)Zeta 電位 (5) 結構 形態 (6) 油水分配係數，來探討促進劑在細胞膜上的表現，同時使用一已知能干擾細胞膜 的促進劑 linolenic acid (LA) 來做正對照。在兔子眼角膜的穿透實驗中，溫度為 37 度且 p
H 值為 7.4 時，對 14C-estradiol 在 control 、飽和的 OA 、 UA 、 BA 及 LA(1mM) 中之綜合穿透係 數分別為 24.67±1.55, 43.70±1.69, 27.13±1.18, 36.19±1.43 and 36.01±1.39 *10
e-6 cm/sec ，其中只有 UA 無顯著增加。而在 14C-mannitol 的穿透部分，只有 LA(1mM) 有顯 著影響。接著同時改變促進劑的帶電性 (pH 由 7.4 改變為 3) ，發現僅 BA 對 14C-estradiol 的穿透仍具有顯著的影響。至於溫度變化的部分，觀察到各促進劑在不同的溫度下 (4 、 20
、 37 和 45 度 ) ，對 14C-estradiol 的穿透有不同程度的影響，以 OA 隨溫度變化影響最劇。然 而在 Zeta 電位和分配係數實驗中，各促進劑則無明顯差異。進而針對 OA 進行低濃度和逆向 穿透實驗，觀察到 OA 在低濃度下對 14C-estradiol 的促進作用消失；而在逆穿透時， OA 仍 有促進作用，但低於正穿透 ( 正、逆穿透分別增加約 77% 和 61%) 。同時觀察 OA 的形態大小，
發現在不同的 pH 下，其形態有明顯的差異，且在不同的濃度時，有不同的凝聚現象和粒徑 大小。結合上述的實驗結果，推測這些 triterpenoids 促進穿透的機制為：以插入的方式 進入脂雙層中，進而干擾細胞膜產生促進作用。
To test the possibility of triterpenoids on cornea tissue fluidity as
well as to modify enhancement by the alternation of physicochemical propertie s of triterpenoids. Methods. Oleanolic acid (OA), Ursolic acid (UA) and Betuli nic acid (BA) were chosen to perturb the cornea tissue by transcellular marker (14C- estradiol) and paracellular marker (C- mannitol), for evaluation the me mbrane integrity and properties. In addition, cornea was treated with Linoleni c acid (LA), well-known membrane perturbation agent, for comparison. A series of different temperatures (4C, 20C, 37C and 45C), charge density, size, zeta p otential, partition coefficient and structure of these reagents were monitored influentially ability. Results. Transcellular marker had shown that the appar ent permeability coefficients of saturated OA, BA and LA (1mM) at 37C were l arger than control(24.67±1.55*10e-6 cm/sec), 43.70±1.69, 36.19±1.43 and 36.
01±1.39*10e-6 cm/sec, respectively, except UA(27.13±1.18*10e-6 cm/sec). On t he other hand, only LA could affect paracellular marker at 37C condition. Af ter modified the charge density (pH=7.4 to 3) of enhancers, OA and LA enhancem ent were disappered, not BA. Different influence patterns of temperature on es
tradiol permeability of cornea by OA, UA, BA and LA were observed and OA was o bserved most sensitivity by thermostat change. Following opposite tansport of
OA on cornea was also shown increment of estradiol permeability and it didn't affect on low concentration performance. In the meantime, under SEM performanc e of OA at pH 7.4 and 3, aggregation of OA particle was observed at different pattern. However, the zeta potential and partition coefficient examinations we re not much different among the all tests for these enhancers. Conclusions. OA , UA, BA and LA revealed different perturbation on different temperature and p H condition. We proposed the enhancement mechanism of these perturbation agent s are interference the cornea tissues by inserting OA among the lipid bilayer.
Perturbation effect of triterpenoids on cornea trans port:by physico-chemical properties
