Region-selective biosynthesis of artemisinic acid glycosides by crown galls of Panax quinquefolium and their in vitro antitumor activities.

BACKGROUND

The biosynthesis of artemisinin derivatives is one of the interesting subjects. Artemisinic acid (AA) has been widely studied as a supposed intermediate in the biosynthetic pathway leading to artemisinin in Artemisia annua.

OBJECTIVE

To investigate the bioconversion of AA by transgenic crown galls of Panax quinquefolium.

METHODS

AA was administered into crown galls of P. quinquefolium and co-cultured for 2 days. The methanol extract was separated by column chromatography, and the structures of two biosynthesis products were elucidated by physicochemical and spectroscopic methods. Co-culture time curves on conversion were also established. In addition, the effects of AA on the growth and ginsenosides production of crown galls of P. quinquefolium were investigated. Furthermore, the in vitro antitumor activities of AA and two glycosides against HepG2 cell line were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay.

RESULTS

Glycosylation of AA by crown galls of P. quinquefolium was observed, and two region-selectively glycosylated products were obtained (AA-1, AA-2), involving one new compound (AA-2). Their structures were elucidated to be AA β-D-glucopyranosyl ester (AA-1) and AA β-D-glucopyranosyl-(2 → 1)-β-D-glucopyranosyl ester (AA-2). The maximum yield of AA-1 was 19.3% on the 1(st) co-culture day while that of AA-2 was 59.1% on the 2(nd) day. MTT assay showed that the activity of monosaccharide glycoside (AA-1) was better than that of disaccharide glycoside (AA-2).

CONCLUSIONS

Two AA glycosides involved one new compound with potential antitumor activity were obtained by region-selective biosynthesis with crown galls of P. quinquefolium.