Bileşiminde nikotin ve 4 bine yakın zehirli madde bulunan tütün bitkisinin kıyılmış, kurutulmuş ve kullanılmaya hazır duruma getirilmiş yaprağından sigara yapılır.
I'm not sure if the meaning will change or not, but I think the text says; "the plant of tobacco contains nicotine and approximately 4000 toxic subtances, and its minced, dried and ready for use tabacco leaves are used to make cigarettes."
So the thing containing nicotine and approximately 4000 toxic subtances is the plant of tobacco, not the leaves of tobacco.