Quercetin是一種廣泛存在植物中的類黃酮，有研究指出這個化合物可能是一種具有生物活性的分子，可以作為抗氧化劑及訊號傳遞分子。在先前的研究觀察到quercetin可以降低在A549細胞中高劑量β-carotene所誘發的促傷害，及增加低劑量β-carotene對抗BaP傷害的保護效果。但quercetin在體內是否可以調節或影響β-carotene的效果並不清楚，所以我們用沙鼠進行本實驗，觀察在有無BaP處理下，β-carotene及quercetin在肝臟及肺臟的分佈情形，及β-carotene及quercetin是否有交互作用。我們選擇沙鼠作為此實驗的動物是因為有研究指出此物種可以像人類一樣完整的吸收膳食中的β-carotene並且於血漿及組織中可偵測的到。結果顯示可以在肝臟及肺臟中偵測到β-carotene及quercetin或quercetin的代謝產物。補充高劑量（非低劑量）β-carotene可以顯著的增加β-carotene在肝臟中達476％；而兩個劑量的補充均會在肺臟中增加約45％；補充quercetin在肝臟增加448％及肺臟中增加340％。當沙鼠以BaP處理後，肝臟中quercetin會減少β-carotene的消耗，而β-carotene亦可保護quercetin被消耗；在肺臟中我們觀察亦觀察到β-carotene會減少quercetin的消耗量。沙鼠在BaP處理下，會顯著或輕微的增加肝臟及肺臟中之TBARS。在BaP處理下，只有quercetin顯著的減少TBARS的產生，而高劑量的β-carotene只有輕微的影響。在抑制TBARS的產生上，β-carotene和quercetin合併使用有相加的效果。總結以上發現，在沙鼠實驗顯示β-carotene及 quercetin可能可以降低彼此在體內由BaP誘發的損耗，而合併這兩個化合物可以相加性的抑制肝臟及肺臟中TBARS的產生。
Quercetin is a flavonoid that ubiquitously present in plant foods. This phytochemical compound has been reported possibly to be a useful bioactive compound of the human diet, both as an antioxidant and as a signalling molecule. In the previous studies, it has been shown that quercetin attenuates the pro-oxidative or harmful effects of high dose β-carotene (20 μM) and enhances the preventive effects of low doseβ-carotene (2μM) on the damage of A549 cells induced by smoke-related carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and benzo[a]pyrene (BaP). However, whether quercetin modulates the effects of β-carotene in vivo is unclear. Thus, we conducted feeding studies in gerbils with or without treated by BaP and determined the levels of β-carotene, total quercetin and TBARS in livers and lungs of gerbils to investigate the interaction of quercetin andβ-carotene. We chose gerbils as an in vivo model because this species has been shown to absorb dietary β-carotene intact and to accumulate β-carotene in tissue and sera like humans. The results showed thatβ-carotene and the metabolites of quercetin distributed in livers and in lungs of gerbils. The supplementation of high dose of β-carotene (10 mg/kg b.w.) rather than low dose (4 mg/kg b.w.) significantly increased the level of β-carotene in liver by 476%; two doses of β-carotene significantly increased the level of β-carotene in lungs by 45%. The supplementation of quercetin increased the level of quercetin in livers and in lungs by 448% and 340%, respectively. When gerbils were treated with BaP, quercetin decreased the consumption of β-carotene and β-carotene also had a protective effect on the consumption of quercetin in liver; in lungs, we only observed that β-carotene decreased the consumption of quercetin. BaP significantly or slightly increased the production of thiobarbituric acid reactive species (TBARS) in livers and in lungs of gerbils. Quercetin alone significantly decreased the formation of TBARS induced by BaP, whereas high dose of β-carotene only had a slight effect. Combination of quercetin and β-carotene had an additive effect on suppressing the formation of TBARS. In conclusion, the gerbil feeding study demonstrated that quercetin and β-carotene may decrease the consumption of each other induced by BaP in vivo, and the combination of these two compounds additively decreased the formation of TBARS in livers and in lungs.
