Glucosylation of cyclodextrin-complexed podophyllotoxin by cell cultures of Linum flavum L.

Abstract

The glucosylation of the cytotoxic lignan podophyllotoxin by cell cultures derived from Linum flavum was investigated. Four cyclodextrins: /3-cyclodextrin, y-cyclodextrin, dimethyl-/3-cyclodextrin and hydroxypropyl-/3-cyclodextrin were used to improve the solubility of podophyllotoxin by complexation. Dimethyl-/3-cyclodextrin met our needs the best and the solubility of podophyllotoxin could be enhanced from 0.15 to 1.92 mM, using a podophyllotoxin/cyclodextrin ratio of 1 : 1. Growth parameters of the cell suspensions were not affected neither by the addition of cyclodextrins alone, nor when complexed podophyllotoxin was dissolved in the medium.The complexed lignan disappeared rapidly from the culture medium, within 24h, under all experimental conditions. Almost simultaneously, between 73 and 100% of detectable podophyllotoxin was bioconverted into podophyllotoxin-/3-D-glucoside. A maximal bioconversion rate of 0.51 mmol 1-1 suspension day -1 was calculated for the L. flavum cells growing in a medium which included the podophyllotoxin/dimethyl-/3-cyclodextrin complex at a final concentration of 1.35 mM.

Deoxypodophyllotoxin 6-hydroxylase, a cytochrome P450 monooxygenase from cell cultures of Linum flavum involved in the biosynthesis of cytotoxic lignans

“…Feeding experiments with cell cultures of Podophyllum hexandrum (accumulating podophyllotoxin as the main lignan) and L.¯avum with 6-methoxypodophyllotoxin as the main lignan showed that P. hexandrum converted deoxypodophyllotoxin into podophyllotoxin whereas L.¯avum accumulated 6-methoxypodophyllotoxinb-D-glucoside after feeding of deoxypodophyllotoxin (Van Uden et al 1995, 1997a. Cell cultures of L.¯avum converted exogenously applied podophyllotoxin to podophyllotoxin-b-D-glucoside and not to 6-methoxypodophyllotoxin (Van Uden et al 1993, 1997a. Feeding of b-peltatin resulted in the formation of 6-methoxypodophyllotoxin-b-D-glucoside and b-peltatin-b-D-glucoside in L.¯avum.…”

The production of podophyllotoxin and its 5-methoxy derivative through bioconversion of cyclodextrin-complexed desoxypodophyllotoxin by plant cell cultures

“…The complexation of desoxypodophyllotoxin with dimethyl-/~-cyclodextrin at a ratio 1:1 and at a concentration of 2 mM was rapid and complete, after 3 h. It has been reported previously that cyclodextrins applied at a concentration of 2 mM did not affect the growth characteristics of cell suspensions of Podophyllurn hexandrum (Woerdenbag et al 1990b) and of Linumflavum (Van Uden et al 1993). Also in this study the use of dimethyl-/~-cyclodextrin at a final concentration of 1.4 mM did not affect the growth characteristics.…”

“…To enable feeding of the very apolar desoxypodophyllotoxin to plant cell cultures in a dissolved state, the substrate was first complexed with dimethyl-~-cyclodextrin (Van Uden et al 1993). The complexation of desoxypodophyllotoxin with dimethyl-/~-cyclodextrin at a ratio 1:1 and at a concentration of 2 mM was rapid and complete, after 3 h. It has been reported previously that cyclodextrins applied at a concentration of 2 mM did not affect the growth characteristics of cell suspensions of Podophyllurn hexandrum (Woerdenbag et al 1990b) and of Linumflavum (Van Uden et al 1993).…”

“…In an earlier study, it was found that dimethyl-/~-cyclodextrin-complexed podophyllotoxin at a comparable concentration and fed to the same cell line of L. flavum, vanished from the medium within 1 day (Van Uden et al 1993). Due to the higher bioconversion rate of podophyllotoxin as compared with desoxypodophyllotoxin, the flux of that substrate into the plant cell might have been higher.…”

“…When podophyllotoxin was fed to cell cultures ofL. flavurn, podophyllotoxinfl-D-glucoside was the only bioconversion product (Van Uden et al 1993). In the present study, with desoxypodophyllotoxin as the substrate using the same cell cultures, neither podophyllotoxin nor its /~-D- Table 1.…”