Study on the Feasibility of Extracting Bioactive Compounds from Melinis minutiflora (Molasses Grass) Using Conventional and Emerging Technology-Assisted Methods

Food color is the first attribute influencing consumer acceptance. In recent years, there has been increasing demand for natural and functional products, challenging the use of synthetic dyes such as Brilliant Blue, Red 40, and Tartrazine. In this context, anthocyanins water soluble pigments ranging from red to purple, stand out as natural colorants with antioxidant potential. Melinis minutiflora (molasses grass), a perennial invasive species in Brazilian ecosystems, produces abundant reddish-purple inflorescences rich in these pigments. Recent studies on anthocyanin extraction highlight emerging technologies that improve yield and process efficiency. Among them, ultrasound treatment applies high-frequency sound waves to disrupt cellular structures, enhancing the release of intracellular compounds. This study aimed to evaluate the effect of high-power ultrasound on the extraction of anthocyanins from M. minutiflora. Eight treatments were conducted: four conventional extractions in 80% ethanol for 24 h, and four using ultrasonic treatment (U) at 850 W and 20 kHz for 1 min. Samples were also divided into non-acidified (P) and acidified (A), and refrigerated (R) or non-refrigerated (Q) groups during extraction. The samples were concentrated using rotary evaporation, colorimetric parameters and total phenolic and anthocyanin contents were analyzed. Colorimetric results showed variations in L*(32.09±0,02 –50.03±0,01), a*(1.33±0,01 –25.08±0,03), and b*(10.53±0,04 –14.92±0,03), with higher values obtained in ultrasound-assisted extractions, indicating improved pigment recovery. In general, ultrasonic treatment enhanced extraction efficiency, producing higher phenolic contents than solvent-only methods. For example, UQP and QP treatments yielded 0.30 and 0.09 mg gallic acid equivalents per liter, respectively. In contrast, URP and RP samples yielded 0.18 and 0.25 mg gallic acid equivalents per liter respectively, showed that ultrasound at neutral pH may promote phenolic degradation. The treatment AUR provided the highest anthocyanin concentrations (331.45 and 217.25 mg cyanidin-3-glucoside per mL of extract), confirming that acidic conditions favor anthocyanin extraction and stability. Overall, extraction with 80% acidified ethanol combined with probe-type ultrasound and refrigeration produced higher levels of bioactive compounds compared with conventional methods, demonstrating that ultrasound-assisted extraction is an efficient and sustainable technique for recovering anthocyanins from Melinis minutiflora.