Biology and Life Sciences Forum (Oct 2023)
Rosemary Essential Oil Extraction and Residue Valorization by Means of Polyphenol Recovery
Abstract
The increasing demand for natural bioactive ingredients extracted from Aromatic and Medicinal Plants (AMPs) has produced disposal problems associated with residual solid waste. One of the main sectors interested in the exploitation of AMPs is the Essential Oils (EOs) industry. Despite EOs being the main commodity in the EOs industry, they only represent a small part of AMPs, generally less than 5% (w/w). This results in the production of a remarkable quantity of biomass that has no apparent commercial value and is therefore underestimated and underutilized by the EOs industry. Among AMPs, Rosmarinus officinalis L., commonly known as rosemary and belonging to the Lamiaceae family, is an aromatic plant endemic to the coastal area of the Mediterranean region but spread worldwide. Rosemary can be cultivated or grow wild as an ornamental evergreen shrub. Their leaves are usually used fresh or dried to flavor foods, mostly in traditional Mediterranean gastronomy, and recently, rosemary extracts were approved for use as food additives in Europe. The antioxidant activity of rosemary leaves has been acknowledged and is ascribed to EOs and polyphenolic compounds. To the best of our knowledge, the optimization of polyphenol recovery from rosemary residues after EO extraction has not yet been investigated. Hence, for the present study, EO extraction from rosemary leaves was performed using the hydro-distillation method, and the antioxidant (EC50) and sun-protective (measured in SPF) activities were evaluated. The polyphenolic fraction was extracted from the rosemary residue under specific experimental variables. In particular, tests were conducted at different extraction times (15 min, 30 min, and 60 min), temperatures (25 °C, 40 °C, 50 °C, 60 °C, and 70 °C), and ethanol concentrations (50%, 60%, 70%, and 80%). In this study, an EO yield of 1.57% was obtained, and the EO had an EC50 value of 240.39 µL/mL and a SPF of 2.55. The maximum amount of polyphenols extracted from the rosemary residue was 24.14 mg GAE/g DW, achieved by using an 80% ethanolic solution at 70 °C for 60 min. This preliminary study reveals how the exploitation and consequential valorization of AMP solid waste may represent new answers for circular economy strategies adopted by European countries.
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