the applicability of the proposed neutralization stepwas demonstrated for parallel screening of antimicrobial sub-stances in 20 commercially available herbal extracts (Fig. 6). Theextracts were applied on the HPTLC plate and developed witha 1-% acidic mobile phase. The developed plate was neutralizedas described in method 5 (Section 3.4) and subjected to the B. s.bioassay. Up to eleven antimicrobial zones were discovered in par-allel in Iris, sundews, centaury, blueberry leaves and white birchtree leaves. Owed to this neutralization step, the limitation of thesolvent selection was overcome and acidic mobile phases can beapplied routinely, as demonstrated. This improvement is also appli-cable to other bioassays, such as the A. fischeri bioassay