Evaluation of spectrophotometric methods for screening of green rooibos (Aspalathus linearis) and green honeybush (Cyclopia genistoides) extracts for high levels of bio-active compounds
ARC Infruitec-Nietvoorbij, Private Bag X5026, Stellenbosch, 7599, South Africa; Department of Food Science, Stellenbosch University, Private Bag XI, Matieland, Stellenbosch 7602, South Africa
The potential of UV spectrophotometry and an aluminium chloride (AlCl3) colorimetric method to determine the dihydrochalcone (DHC) and mangiferin contents of green rooibos and honeybush (C. genistoides) extracts, respectively, was investigated. The DHC content of rooibos water extracts, determined using UV spectroscopy, correlated with the sum of the aspalathin and nothofagin contents as quantified using HPLC (r = 0.98). A correlation coefficient of 0.91 was obtained when correlating the mangiferin content of C. genistodies methanol extracts, determined by the AlCl3 colorimetric method, with the results obtained by HPLC. Using the linear equations from the correlations it was possible to predict the DHC and mangiferin contents of extracts from the respective spectrophotometric measurements to a reasonable accuracy as an alternative to HPLC. The total polyphenol (TP) content of rooibos water extracts can also be determined using UV spectrophotometry and aspalathin as a standard (r = 0.99) as an alternative to the Folin-Ciocalteau method. The TP content of rooibos extracts correlated (r = 0.99) with its total antioxidant activity (TAA) as determined with the ABTS radical cation scavenging assay, but the TP content of C. genistoides water extracts is not a good indication of their TAA (r = 0.27). The aspalathin content of rooibos extracts correlated with their TAA (r = 0.96), but the mangiferin content of honeybush water extracts only gave a moderate correlation with their TAA (r = 0.75). Copyright © 2007 John Wiley & Sons, Ltd.
aluminum chloride; antioxidant; aspalathin; Aspalathus linearis extract; chalcone derivative; Cyclopia genistoides extract; dihydrochalcone; mangiferin; methanol; natural product; nothofagin; plant extract; polyphenol; unclassified drug; accuracy; antioxidant activity; article; Aspalathus; Aspalathus linearis; colorimetry; correlation analysis; correlation coefficient; Cyclopia genistoides; drug screening; drug structure; high performance liquid chromatography; linear system; prediction; quantitative analysis; scavenging system; ultraviolet spectrophotometry; Aluminum Compounds; Aspalathus; Chalcones; Chlorides; Chromatography, High Pressure Liquid; Colorimetry; Cyclopia Plant; Molecular Structure; Plant Extracts; Spectrophotometry, Ultraviolet; Water; Xanthones; Aspalathus linearis; Cyclopia genistoides