Biosynthetic origin of alkylated decaline-type polyketides and induction of a new metabolite by addition of benzoate in cultured mycobionts of Pyrenula sp.

•The biogenetic origin of pyrenulic acid C was verified by feeding experiments.•The cultured mycobionts produced pyrenulic acid I by addition of benzoate to medium.•The structure of pyrenulic acid I was spectroscopically determined.