Under heavy metal stress, root endophytes are known to confer heavy metal tolerance to their host plants. Recently, siderophores, low molecular weight compounds with metal-chelating activity, have been reported to function as detoxicants for heavy metals in plants. In the present study, we investigated the functions of metabolites produced by the root endophyte, Pezicula ericae, isolated from Aucuba japonica Thunb., naturally growing at a mine site and containing high concentration of Zn in roots. We evaluated the Zn solubilization activities of P. ericae on malt extract agar media containing ZnO and Zn₃(PO₄)₂, and isolated the siderophore via chrome azrol S (CAS) assay and column chromatography. Finally, we conducted nuclear magnetic resonance analysis to elucidate the relative configuration of the compound. As a result, all isolates used for the assay showed Zn solubilization activities and P. ericae w12-25 showed the highest Zn solubilization activity, suggesting that these endophytes might contribute to the Zn toxicity alleviation within A. japonica roots. It was also clarified that the siderophore was a novel compound, a derivative of avenaciolide. We named this compound as avenaciol and discussed the functions of this compound for the heavy metal tolerance of A. japonica and P. ericae.