Complex sentence: The nut of the horse-chestnut tree ("Aesculus " species, especially"Aesculus hippocastanum"), called chestnuts in the British Isles are inedible because they contain toxic glucoside aesculin.
Split into simpler sentences: The nut of the horse-chestnut tree ("Aesculus " species, especially"Aesculus hippocastanum"), called chestnuts in the British Isles. Conkers are inedible because they contain toxic glucoside aesculin.