Fig. 5 Transformation of UA by Nocardia sp. NRRL 5646
Moreover, UA has been well modified by various fungi59. Aspergillus flavus (ATCC 9170) was able to convert UA into the new natural product 3-oxo-UA derivative with C-3 hydroxylation (Fig. 6A ) 60. In addition, four UA derivatives have been produced by Syncephalastrum racemosum(Cohn) Schroter AS3.264 61, indicating the inhibitory effect against protein tyrosine phosphatase 1B (Fig. 6C ). UA was also biotransformed into six glycosylated and hydroxylated products by an endophytic fungi Alternaria longipes AS3.287562. One of the resultant new compounds, 28-o-β-d-glucopyranosyl-3-oxo-UA, showed stronger antibacterial activity against Staphylococcus aureus and methicillin-resistantStaphylococcus aureus (Fig. 6B ). Liu et al.obtained three new derivatives transformed by Mucor spinosusAS3.3450 63(Fig.6D ). Among them, 3β,7β,21β-trihydroxy-UA showed stronger cytotoxicity against HeLa cells, K562 cells and KB cells, enlightening its potential therapeutic role in anticancer therapy.