n-Butanol/HCl assay: n-Butanol/HCl assay was carried
out according to a slightly modified method of Vemerris
[19]. In brief, to 0.1 mL of samples was added 1 mL of an
acidic solution of ferrous sulfate [7.7 mg of FeSO4.7H2O
dissolved in 50 mL of conc. HCl- n-butanol (2:3, v/v)].
The mixtures, loosely sealed in test tubes, were placed in a
water bath 95C for 15 min.