為什麼切洋蔥會讓人流眼淚？ 當洋蔥被切開時，釋放出的哪種揮發性含硫化合物會刺激眼睛？ Why do onions make you cry? What volatile sulfur compound is released when an onion is cut that irritates the eyes?
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丙硫醛 S-氧化物 / Syn-propanethial S-oxide 當洋蔥細胞破裂時，酵素會將胺基酸轉化為丙硫醛 S-氧化物，接觸到眼淚後會形成微量硫酸而刺激眼淚分泌。 When onion cells rupture, enzymes convert amino acids into syn-propanethial S-oxide, which forms trace sulfuric acid upon contacting tears and stimulates crying.