Identity issues surrounding American skullcap (Scutellaria lateriflora) and an optimised high performance liquid chromatography method to authenticate commercially available products

Abstract

Traditional use of American skullcap (Scutellaria lateriflora) for anxiety and related conditions is well documented. There is evidence of flavonoid instability in S. lateriflora and a high rate of substitution with other skullcap species or adulteration with potentially hepatotoxic germanders (Teucrium spp.). It is therefore essential for the identity, quality and safety of a commercial S. lateriflora product to be verified prior to clinical use. The objective was to review the literature relating to substitution and adulteration of S. lateriflora and to present a simple, optimised high performance liquid chromatography (HPLC) method to verify the absence of adulterants in a commercial sample of S. lateriflora, by comparing its chromatographic profile with that of authenticated S. lateriflora. S. lateriflora reference material and a freeze-dried commercial sample were extracted with methanol and water (80:20, v/v) and compared by HPLC analysis. The commercial sample showed reproducible retention times (RTs) of the flavonoid biomarkers baicalin (RT = 14.8 min; mean ± SD = 11.71 ± 1.16 mg/g); baicalein (RT = 20.4 min; 7.67 ± 0.89 mg/g); wogonin (RT = 23.7 min; 0.65 ± 0.06 mg/g). It appeared to be free from adulteration with germander (verbascoside was not detected; RT = 9.1 min) and its phytochemical profile was consistent with that of the S. lateriflora reference material. It is crucial that commercial products are adequately identified prior to use. The reported HPLC method has shown the potential to compare non-authenticated S. lateriflora samples with authenticated voucher specimens – essential when conducting any phytochemical analysis of the herb.