Strictosidine‐related enzymes involved in the alkaloid biosynthesis of Uncaria tomentosa root cultures grown under oxidative stress

The activity and gene expression of strictosidine‐related enzymes in Uncaria tomentosa root cultures exposed to oxidative stress were studied. Elicitation with 0.2 mM hydrogen peroxide (H 2 O 2 ) or a combination of 0.8 mM buthionine sulfoximine and 0.2 mM jasmonic acid (BSO‐JA) increased peroxidase activities by twofold at Day 8 and glutathione reductase by 1.4‐fold at Day 5 in H 2 O 2 elicited cultures respect to the control. Production of monoterpenoid oxindole alkaloids (MOA), 3α‐dihydrocadambine, and dolichantoside was stimulated after H 2 O 2 elicitation, reaching levels of 886.4 ± 23.6, 847.7 ± 25.4, and 87.5 ± 7.2 µg/g DW, at Day 8 which were 1.7‐, 2.1‐, and 2.3‐fold higher relative to control. BSO‐JA elicited cultures produced about twice alkaloids than H 2 O 2 ‐treated cultures, following a biphasic pattern with maxima at 0.5 and 8 days. Alkaloid production was preceded by increase in strictosidine synthase (STR) and strictosidine glucosidase (SGD) activities. After elicitation with H 2 O 2 or BSO‐JA, the STR activity (pKat/mg protein) increased by 1.9‐fold (93.8 ± 17.8 at 24 h) or 2.5‐fold (102.4 ± 2.2 at 6 h) and the SGD activity (pKat/mg protein) by 2.8‐fold (245.2 ± 14.4 at 6 h) or 4.2‐fold (421.2 ± 1.8 at 18 h) relative to control. STR and SGD transcripts were upregulated after elicitation. H 2 O 2 ‐treated roots showed higher levels of STR at 48–192 h and SGD at 24–48 h, while BSO‐JA treatments showed STR increased at 12 h and SGD at 24 h. Also, LC/ESI‐MS confirmed the biosynthesis of dolichantoside from N ‐ω‐methyltryptamine and secologanin by U. tomentosa protein extracts. © 2013 American Institute of Chemical Engineers Biotechnol. Prog ., 29:621–630, 2013