Abstract:
Polyphenols are micronutrients which has nutritional value owing to their antioxidant
activity. Polyphenol content is usually determined by the standard Folin-Denis
Assay. Water soluble compounds commonly present in biological samples, such as
proteins, ascorbic acid, DNA and RNA may interfere with this assay. Therefore, it is
difficult to determine whether the antioxidant capacity of such samples are owing to
these interfering compounds or other polyphenols present in the aqueous extracts
(AE) like coconut milk (CM). In order to overcome these drawbacks, a modified
extraction method was employed to remove proteins from the AE of CM to determine
the polyphenol content in first (FE) and second (SE) extracts of both domestic and
commercial preparations of CM using Folin-Denis assay. The results were reported
as Gallic acid equivalents (mg/mL). Proteins/peptides present in the AE of CM (1.00
mL) was removed by organic extraction with chloroform (1.00 mL), distilled water
(4.00 mL) and methanol (4.00 mL). Samples were mixed at 30 Hz for 01 min
followed by centrifugation at 6000 rpm for 05 min. The methanolic layer was used
for the Folin-Denis assay. The methanolic extracts (ME) were confirmed free of
proteins by Bradford assay. Results showed significantly low polyphenol content in
the ME compared to the AE indicating interference in the assay from
proteins/peptides present in the AE of CM. Corresponding antioxidant activity of the
ME of both FE and SE of domestic CM preparations were significantly higher
compared to the commercial counterparts regardless of the presence of high
polyphenol content in the AE. Therefore, the modified Folin-Denis assay reported
here determine the polyphenol content in AE of food preparations that may
contribute to their antioxidant potential.
