To 0.5 ml of clear supernatant was added 5.0 ml of
anthrone reagent, and the combination was boiled for 10 min in a water bath.
We determined the total sugar content in each nectar sample (wick) using a colorimetric
anthrone assay modified for microliter volumes (Cipollini et al., 1994).
Free sugars and polysaccharides were determined separately by colorimetry using
anthrone reagent (Clegg 1956).
Determination of dextran with
anthrone. Anal Chem 1953;25:1656-61.
Three milliliters of
anthrone reagent (150 mg anthrone/100 mL of 72% sulfuric acid) was then added to each tube and tubes were incubated in a water bath at 90 [degrees] C for 20 min.
Briefly, extract was mixed with 80% hot ethanol, centrifuged and mixed with
anthrone reagent.
The total carbohydrate contents were estimated using standard
Anthrone method [28] and the contents were calculated from the standard graph curve of glucose.
0.1 mL supernatant was added to 0.4 mL freshly prepared
anthrone reagent at 100 for 10 min and cooled to room temperature in an ice bath.
The products of this reaction condense with the
anthrone, forming a colored teal substance that is used for the reading of soluble sugars made in spectrophotometer (FEMTO, Cirrus 80ST), at 620 nm.
Carbone was quantified by the
Anthrone method, after precipitation of proteins with trichloroacetic acid (Roe, 1955).
Freshly prepared
anthrone (3 ml) was added to 0.1 ml supernatant.
The biosynthetic pathway leading to hypericins starts with the condensation of one molecule of acetyl-CoA with seven molecules of malonyl-CoA to form an octaketide chain that subsequently undergoes cyclizations and decarboxylation to form emodin
anthrone. These reactions are carried out by two polyketide synthases (HpKS1 and HpKS2) having octaketide synthase activity [53].