Assessment of the presence of damiana in herbal blends of forensic interest based on comprehensive two-dimensional gas chromatography

The popularity of 'herbal highs' as an alternative to common illegal drugs is becoming an emerging concern for forensic laboratories and medical facilities. One of the herbal ingredients often claimed by the suppliers to be present in their products is Turnera diffusa, commonly known as 'damiana,' which has a long history as a pharmaceutical drug and an intoxicating substance due to its alleged psychoactive effects. The present project focused on the analysis of the chemical signature of damiana for its identification in different herbal blends of forensic interest. Comprehensive two-dimensional gas chromatography proved to be a powerful tool for the extensive analysis of the wide range of volatile compounds present in extracts of damiana and related herbal products. Due to the absence of unique compounds in Turnera diffusa, the chemical pattern has to be considered to ascertain the presence of this species in herbal blends. Differentiation to the closely related species Turnera ulmifolia was provided based on the chemical profile. Compound alignment based on both retention times and mass spectral data revealed the presence of damiana in all 'herbal high' products, regardless of whether the presence was declared on the product or not. For several blends, damiana appeared to be the exclusive herbal component. Thus, it confirms the presumption that Turnera diffusa is one of the preferred herbs used as a matrix for 'herbal high' products. Utilizing principle component analysis, 31 compounds were selected, which provided discrimination of five commercial damiana batches.