This is the 11149th most frequent Turkish word.
duyurduğu
"That which he/she/it announced."
The word 'duyurduğu' is a conjugation from the verb 'duyurmak' (to announce) used in possessive participle form, qualifying the direct action of announcing by the mayor.
Gazeteler, belediye başkanının yeni projeyi duyurduğunu yazdı.
The newspapers wrote that the mayor announced the new project.
Here, 'duyurduğu' describes the products previously announced by the company, showing an action performed earlier.
Şirket, duyurduğu ürünlerin tanıtımına başladığını açıkladı.
The company announced that it has started the promotion of the products it had previously disclosed.
In this sentence, 'duyurduğu' modifies 'arkadaşlarının', signifying that he/she had mentioned these friends previously in an announcement.