Novel approaches to exploring nutritional potential and applications of residual biomass after essential oil extraction: case study of Ammodaucus leucotrichus

The residual biomass (RB) remaining after essential oil (EO) extraction from plants hold significant potential for various applications, particularly in cosmetics. This study investigates the RB of Ammodaucus leucotrichus (AL) seeds, to assess its suitability for skin-care formulations. We compare the effects of three EO extraction methods Microwave-Assisted Extraction (MAE), Steam Distillation (SD), and Water Distillation (WD), on the composition of the biomass and their potential valorization for cosmetic use. Proximate analysis (PA) revealed that the RB retained a high carbohydrate content, ranging from 60.85% to 63.00%, after EO extraction, while protein levels slightly decreased from 11.03% to 9.90%. The RB also preserved significant free sugars, including fructose, glucose, and sucrose, with minimal variation across extraction methods. Organic acids, which contribute to skin exfoliation and antioxidant effects, showed only slight reductions: oxalic acid decreased from 0.88 g/100 g to 0.82 g/100 g, malic acid from 2.11 g/100 g to 1.98 g/100 g, and ascorbic acid from 5.89 mg/100 g to 5.50 mg/100 g. Scanning Electron Microscopy (SEM) images showed that WD and SD methods maintained the structural integrity of the plant tissue with only minor damage, making these methods suitable for cosmetic applications where the stability of bioactive compounds is essential. In contrast, MAE caused significant ruptures in the biomass tissue. While these ruptures enhanced extraction efficiency, they could potentially compromise the stability of certain sensitive bioactive compounds, impacting their suitability for cosmetic applications. Nonetheless, MAE still preserved essential macro-elements (calcium, magnesium, potassium) and microelements (zinc, copper, iron), which are beneficial for skin health. Overall, the results demonstrate that the RB from EO extraction contains valuable bioactive compounds, including carbohydrates, free sugars, organic acids, and essential minerals, making it a promising resource for cosmetic applications. The study underscores the importance of choosing the right EO extraction method to maintain the integrity of these bioactive components and guarantee their bioactivities.