Purificação de extrato de alfavaca-cravo (Ocimum gratissimum L.) utilizando processo de filtração por membranas

Abstract

Using neglected and underutilized species present greater diversity in obtaining micronutrients and bioactive compounds with antioxidant properties. Clove basil (Ocimum gratissimum L.), a medicinal plant found in tropical areas and already used in folk medicine, has the potential to advance in the productive chair, generating herbal medicines and functional foods. Obtaining phytochemicals is usually performed by extraction processes followed by a purification process. Membrane separation processes stand out as clarification and purification processes granting a quality product without losing the essential properties of bioactive compounds. This work aims to evaluate ultrafiltration with polymeric membranes to clarify the aqueous extract of clove basil. To improve the quality of the membrane, we also proposed coating a membrane with graphene oxide and evaluating its performance in the filtration of the same extract. The extraction of phenolic compounds was performed at 75 °C for 120 min using a solid-liquid ratio of 1 g of dry leaves to 100 mL of solvent. The membranes used in the extraction process were 10 kDa and 150 kDa polyethersulfone membranes and a 150 kDa membrane coated with graphene oxide solution. The crude extract was characterized as to the content of total phenolic compounds (340.22 ± 1.82 mgEAG∙gextract-1), antioxidant capacity (2493.54 ± 77.61 μMET∙gextract-1 for the DPPH assay and 2597.10 ± 175.52 μMET∙gextract-1 for the ABTS assay), to the colour, turbidity (29.5 ± 2.1 NTU), to the content of total solids (0.230 ± 0.038 %) and other relevant analyzes. The 10 kDa membrane filtration process made it possible to remove 64% of total solids and 84% of turbidity and maintained 50% of the content of total phenolic compounds in the permeate. The 150 kDa membrane filtration process maintained 60% of the content of total phenolic compounds and removed 27% of total solids and 30.5% of turbidity. The membrane coated with graphene oxide created a greater restriction on the passage of extract flow and showed an intrinsic resistance 225 times greater than the membrane without coating. In the flow decay analysis, the largest contributor to the 10 kDa membrane operation was cake formation, while all mechanisms contributed to the flow decay in the 150 kDa membrane operation. Regarding the series resistance model, concentration polarization caused a greater effect of resistance on 10 kDa and 150 kDa membranes, while the combined action of reversible and irreversible fouling caused the highest resistance in the coated membrane. Using more restrictive membranes was efficient to concentrate bioactive compounds, such as catechins and low molecular-weight phenolic acids. Finally, ultrafiltration presented itself as an efficient process to clarify the clove basil extract and follows as a promising process of clarification of various extracts.