Catalyzes the glutathione-dependent reduction of S-glutathionylquercetin to quercetin. In vitro, possesses glutathione-dependent thiol transferase activity toward 2-hydroxyethyl disulfide (HED). glutathione + RX = a halide anion + an S-substituted glutathione + H(+) By glutathione, ascorbate and auxin. Belongs to the GST superfamily. Lambda family.